from __future__ import print_function, division

import itertools

from sympy.core import S
from sympy.core.containers import Tuple
from sympy.core.function import _coeff_isneg
from sympy.core.mod import Mod
from sympy.core.mul import Mul
from sympy.core.numbers import Rational
from sympy.core.power import Pow
from sympy.core.relational import Equality
from sympy.core.symbol import Symbol
from sympy.printing.precedence import PRECEDENCE, precedence, precedence_traditional
from sympy.utilities import group
from sympy.utilities.iterables import has_variety
from sympy.core.sympify import SympifyError
from sympy.core.compatibility import range
from sympy.core.add import Add

from sympy.printing.printer import Printer
from sympy.printing.str import sstr
from sympy.printing.conventions import requires_partial

from .stringpict import prettyForm, stringPict
from .pretty_symbology import xstr, hobj, vobj, xobj, xsym, pretty_symbol, \
    pretty_atom, pretty_use_unicode, pretty_try_use_unicode, greek_unicode, U, \
    annotated

from sympy.utilities import default_sort_key

# rename for usage from outside
pprint_use_unicode = pretty_use_unicode
pprint_try_use_unicode = pretty_try_use_unicode


class PrettyPrinter(Printer):
    """Printer, which converts an expression into 2D ASCII-art figure."""
    printmethod = "_pretty"

    _default_settings = {
        "order": None,
        "full_prec": "auto",
        "use_unicode": None,
        "wrap_line": True,
        "num_columns": None,
        "use_unicode_sqrt_char": True,
    }

    def __init__(self, settings=None):
        Printer.__init__(self, settings)
        self.emptyPrinter = lambda x: prettyForm(xstr(x))

    @property
    def _use_unicode(self):
        if self._settings['use_unicode']:
            return True
        else:
            return pretty_use_unicode()

    def doprint(self, expr):
        return self._print(expr).render(**self._settings)

    # empty op so _print(stringPict) returns the same
    def _print_stringPict(self, e):
        return e

    def _print_basestring(self, e):
        return prettyForm(e)

    def _print_atan2(self, e):
        pform = prettyForm(*self._print_seq(e.args).parens())
        pform = prettyForm(*pform.left('atan2'))
        return pform

    def _print_Symbol(self, e):
        symb = pretty_symbol(e.name)
        return prettyForm(symb)
    _print_RandomSymbol = _print_Symbol

    def _print_Float(self, e):
        # we will use StrPrinter's Float printer, but we need to handle the
        # full_prec ourselves, according to the self._print_level
        full_prec = self._settings["full_prec"]
        if full_prec == "auto":
            full_prec = self._print_level == 1
        return prettyForm(sstr(e, full_prec=full_prec))

    def _print_Cross(self, e):
        vec1 = e._expr1
        vec2 = e._expr2
        pform = self._print(vec2)
        pform = prettyForm(*pform.left('('))
        pform = prettyForm(*pform.right(')'))
        pform = prettyForm(*pform.left(self._print(U('MULTIPLICATION SIGN'))))
        pform = prettyForm(*pform.left(')'))
        pform = prettyForm(*pform.left(self._print(vec1)))
        pform = prettyForm(*pform.left('('))
        return pform

    def _print_Curl(self, e):
        vec = e._expr
        pform = self._print(vec)
        pform = prettyForm(*pform.left('('))
        pform = prettyForm(*pform.right(')'))
        pform = prettyForm(*pform.left(self._print(U('MULTIPLICATION SIGN'))))
        pform = prettyForm(*pform.left(self._print(U('NABLA'))))
        return pform

    def _print_Divergence(self, e):
        vec = e._expr
        pform = self._print(vec)
        pform = prettyForm(*pform.left('('))
        pform = prettyForm(*pform.right(')'))
        pform = prettyForm(*pform.left(self._print(U('DOT OPERATOR'))))
        pform = prettyForm(*pform.left(self._print(U('NABLA'))))
        return pform

    def _print_Dot(self, e):
        vec1 = e._expr1
        vec2 = e._expr2
        pform = self._print(vec2)
        pform = prettyForm(*pform.left('('))
        pform = prettyForm(*pform.right(')'))
        pform = prettyForm(*pform.left(self._print(U('DOT OPERATOR'))))
        pform = prettyForm(*pform.left(')'))
        pform = prettyForm(*pform.left(self._print(vec1)))
        pform = prettyForm(*pform.left('('))
        return pform

    def _print_Gradient(self, e):
        func = e._expr
        pform = self._print(func)
        pform = prettyForm(*pform.left('('))
        pform = prettyForm(*pform.right(')'))
        pform = prettyForm(*pform.left(self._print(U('DOT OPERATOR'))))
        pform = prettyForm(*pform.left(self._print(U('NABLA'))))
        return pform

    def _print_Atom(self, e):
        try:
            # print atoms like Exp1 or Pi
            return prettyForm(pretty_atom(e.__class__.__name__))
        except KeyError:
            return self.emptyPrinter(e)

    # Infinity inherits from Number, so we have to override _print_XXX order
    _print_Infinity = _print_Atom
    _print_NegativeInfinity = _print_Atom
    _print_EmptySet = _print_Atom
    _print_Naturals = _print_Atom
    _print_Naturals0 = _print_Atom
    _print_Integers = _print_Atom
    _print_Complexes = _print_Atom

    def _print_Reals(self, e):
        if self._use_unicode:
            return self._print_Atom(e)
        else:
            inf_list = ['-oo', 'oo']
            return self._print_seq(inf_list, '(', ')')

    def _print_subfactorial(self, e):
        x = e.args[0]
        pform = self._print(x)
        # Add parentheses if needed
        if not ((x.is_Integer and x.is_nonnegative) or x.is_Symbol):
            pform = prettyForm(*pform.parens())
        pform = prettyForm(*pform.left('!'))
        return pform

    def _print_factorial(self, e):
        x = e.args[0]
        pform = self._print(x)
        # Add parentheses if needed
        if not ((x.is_Integer and x.is_nonnegative) or x.is_Symbol):
            pform = prettyForm(*pform.parens())
        pform = prettyForm(*pform.right('!'))
        return pform

    def _print_factorial2(self, e):
        x = e.args[0]
        pform = self._print(x)
        # Add parentheses if needed
        if not ((x.is_Integer and x.is_nonnegative) or x.is_Symbol):
            pform = prettyForm(*pform.parens())
        pform = prettyForm(*pform.right('!!'))
        return pform

    def _print_binomial(self, e):
        n, k = e.args

        n_pform = self._print(n)
        k_pform = self._print(k)

        bar = ' '*max(n_pform.width(), k_pform.width())

        pform = prettyForm(*k_pform.above(bar))
        pform = prettyForm(*pform.above(n_pform))
        pform = prettyForm(*pform.parens('(', ')'))

        pform.baseline = (pform.baseline + 1)//2

        return pform

    def _print_Relational(self, e):
        op = prettyForm(' ' + xsym(e.rel_op) + ' ')

        l = self._print(e.lhs)
        r = self._print(e.rhs)
        pform = prettyForm(*stringPict.next(l, op, r))
        return pform

    def _print_Not(self, e):
        from sympy import Equivalent, Implies
        if self._use_unicode:
            arg = e.args[0]
            pform = self._print(arg)
            if isinstance(arg, Equivalent):
                return self._print_Equivalent(arg, altchar=u"\N{LEFT RIGHT DOUBLE ARROW WITH STROKE}")
            if isinstance(arg, Implies):
                return self._print_Implies(arg, altchar=u"\N{RIGHTWARDS ARROW WITH STROKE}")

            if arg.is_Boolean and not arg.is_Not:
                pform = prettyForm(*pform.parens())

            return prettyForm(*pform.left(u"\N{NOT SIGN}"))
        else:
            return self._print_Function(e)

    def __print_Boolean(self, e, char, sort=True):
        args = e.args
        if sort:
            args = sorted(e.args, key=default_sort_key)
        arg = args[0]
        pform = self._print(arg)

        if arg.is_Boolean and not arg.is_Not:
            pform = prettyForm(*pform.parens())

        for arg in args[1:]:
            pform_arg = self._print(arg)

            if arg.is_Boolean and not arg.is_Not:
                pform_arg = prettyForm(*pform_arg.parens())

            pform = prettyForm(*pform.right(u' %s ' % char))
            pform = prettyForm(*pform.right(pform_arg))

        return pform

    def _print_And(self, e):
        if self._use_unicode:
            return self.__print_Boolean(e, u"\N{LOGICAL AND}")
        else:
            return self._print_Function(e, sort=True)

    def _print_Or(self, e):
        if self._use_unicode:
            return self.__print_Boolean(e, u"\N{LOGICAL OR}")
        else:
            return self._print_Function(e, sort=True)

    def _print_Xor(self, e):
        if self._use_unicode:
            return self.__print_Boolean(e, u"\N{XOR}")
        else:
            return self._print_Function(e, sort=True)

    def _print_Nand(self, e):
        if self._use_unicode:
            return self.__print_Boolean(e, u"\N{NAND}")
        else:
            return self._print_Function(e, sort=True)

    def _print_Nor(self, e):
        if self._use_unicode:
            return self.__print_Boolean(e, u"\N{NOR}")
        else:
            return self._print_Function(e, sort=True)

    def _print_Implies(self, e, altchar=None):
        if self._use_unicode:
            return self.__print_Boolean(e, altchar or u"\N{RIGHTWARDS ARROW}", sort=False)
        else:
            return self._print_Function(e)

    def _print_Equivalent(self, e, altchar=None):
        if self._use_unicode:
            return self.__print_Boolean(e, altchar or u"\N{LEFT RIGHT DOUBLE ARROW}")
        else:
            return self._print_Function(e, sort=True)

    def _print_conjugate(self, e):
        pform = self._print(e.args[0])
        return prettyForm( *pform.above( hobj('_', pform.width())) )

    def _print_Abs(self, e):
        pform = self._print(e.args[0])
        pform = prettyForm(*pform.parens('|', '|'))
        return pform
    _print_Determinant = _print_Abs

    def _print_floor(self, e):
        if self._use_unicode:
            pform = self._print(e.args[0])
            pform = prettyForm(*pform.parens('lfloor', 'rfloor'))
            return pform
        else:
            return self._print_Function(e)

    def _print_ceiling(self, e):
        if self._use_unicode:
            pform = self._print(e.args[0])
            pform = prettyForm(*pform.parens('lceil', 'rceil'))
            return pform
        else:
            return self._print_Function(e)

    def _print_Derivative(self, deriv):
        if requires_partial(deriv) and self._use_unicode:
            deriv_symbol = U('PARTIAL DIFFERENTIAL')
        else:
            deriv_symbol = r'd'
        x = None
        count_total_deriv = 0

        for sym, num in reversed(deriv.variable_count):
            s = self._print(sym)
            ds = prettyForm(*s.left(deriv_symbol))
            count_total_deriv += num

            if (not num.is_Integer) or (num > 1):
                ds = ds**prettyForm(str(num))

            if x is None:
                x = ds
            else:
                x = prettyForm(*x.right(' '))
                x = prettyForm(*x.right(ds))

        f = prettyForm(
            binding=prettyForm.FUNC, *self._print(deriv.expr).parens())

        pform = prettyForm(deriv_symbol)

        if (count_total_deriv > 1) != False:
            pform = pform**prettyForm(str(count_total_deriv))

        pform = prettyForm(*pform.below(stringPict.LINE, x))
        pform.baseline = pform.baseline + 1
        pform = prettyForm(*stringPict.next(pform, f))
        pform.binding = prettyForm.MUL

        return pform

    def _print_Cycle(self, dc):
        from sympy.combinatorics.permutations import Permutation, Cycle
        # for Empty Cycle
        if dc == Cycle():
            cyc = stringPict('')
            return prettyForm(*cyc.parens())

        dc_list = Permutation(dc.list()).cyclic_form
        # for Identity Cycle
        if dc_list == []:
            cyc = self._print(dc.size - 1)
            return prettyForm(*cyc.parens())

        cyc = stringPict('')
        for i in dc_list:
            l = self._print(str(tuple(i)).replace(',', ''))
            cyc = prettyForm(*cyc.right(l))
        return cyc

    def _print_PDF(self, pdf):
        lim = self._print(pdf.pdf.args[0])
        lim = prettyForm(*lim.right(', '))
        lim = prettyForm(*lim.right(self._print(pdf.domain[0])))
        lim = prettyForm(*lim.right(', '))
        lim = prettyForm(*lim.right(self._print(pdf.domain[1])))
        lim = prettyForm(*lim.parens())

        f = self._print(pdf.pdf.args[1])
        f = prettyForm(*f.right(', '))
        f = prettyForm(*f.right(lim))
        f = prettyForm(*f.parens())

        pform = prettyForm('PDF')
        pform = prettyForm(*pform.right(f))
        return pform

    def _print_Integral(self, integral):
        f = integral.function

        # Add parentheses if arg involves addition of terms and
        # create a pretty form for the argument
        prettyF = self._print(f)
        # XXX generalize parens
        if f.is_Add:
            prettyF = prettyForm(*prettyF.parens())

        # dx dy dz ...
        arg = prettyF
        for x in integral.limits:
            prettyArg = self._print(x[0])
            # XXX qparens (parens if needs-parens)
            if prettyArg.width() > 1:
                prettyArg = prettyForm(*prettyArg.parens())

            arg = prettyForm(*arg.right(' d', prettyArg))

        # \int \int \int ...
        firstterm = True
        s = None
        for lim in integral.limits:
            x = lim[0]
            # Create bar based on the height of the argument
            h = arg.height()
            H = h + 2

            # XXX hack!
            ascii_mode = not self._use_unicode
            if ascii_mode:
                H += 2

            vint = vobj('int', H)

            # Construct the pretty form with the integral sign and the argument
            pform = prettyForm(vint)
            pform.baseline = arg.baseline + (
                H - h)//2    # covering the whole argument

            if len(lim) > 1:
                # Create pretty forms for endpoints, if definite integral.
                # Do not print empty endpoints.
                if len(lim) == 2:
                    prettyA = prettyForm("")
                    prettyB = self._print(lim[1])
                if len(lim) == 3:
                    prettyA = self._print(lim[1])
                    prettyB = self._print(lim[2])

                if ascii_mode:  # XXX hack
                    # Add spacing so that endpoint can more easily be
                    # identified with the correct integral sign
                    spc = max(1, 3 - prettyB.width())
                    prettyB = prettyForm(*prettyB.left(' ' * spc))

                    spc = max(1, 4 - prettyA.width())
                    prettyA = prettyForm(*prettyA.right(' ' * spc))

                pform = prettyForm(*pform.above(prettyB))
                pform = prettyForm(*pform.below(prettyA))

            if not ascii_mode:  # XXX hack
                pform = prettyForm(*pform.right(' '))

            if firstterm:
                s = pform   # first term
                firstterm = False
            else:
                s = prettyForm(*s.left(pform))

        pform = prettyForm(*arg.left(s))
        pform.binding = prettyForm.MUL
        return pform

    def _print_Product(self, expr):
        func = expr.term
        pretty_func = self._print(func)

        horizontal_chr = xobj('_', 1)
        corner_chr = xobj('_', 1)
        vertical_chr = xobj('|', 1)

        if self._use_unicode:
            # use unicode corners
            horizontal_chr = xobj('-', 1)
            corner_chr = u'\N{BOX DRAWINGS LIGHT DOWN AND HORIZONTAL}'

        func_height = pretty_func.height()

        first = True
        max_upper = 0
        sign_height = 0

        for lim in expr.limits:
            width = (func_height + 2) * 5 // 3 - 2
            sign_lines = []
            sign_lines.append(corner_chr + (horizontal_chr*width) + corner_chr)
            for i in range(func_height + 1):
                sign_lines.append(vertical_chr + (' '*width) + vertical_chr)

            pretty_sign = stringPict('')
            pretty_sign = prettyForm(*pretty_sign.stack(*sign_lines))

            pretty_upper = self._print(lim[2])
            pretty_lower = self._print(Equality(lim[0], lim[1]))

            max_upper = max(max_upper, pretty_upper.height())

            if first:
                sign_height = pretty_sign.height()

            pretty_sign = prettyForm(*pretty_sign.above(pretty_upper))
            pretty_sign = prettyForm(*pretty_sign.below(pretty_lower))

            if first:
                pretty_func.baseline = 0
                first = False

            height = pretty_sign.height()
            padding = stringPict('')
            padding = prettyForm(*padding.stack(*[' ']*(height - 1)))
            pretty_sign = prettyForm(*pretty_sign.right(padding))

            pretty_func = prettyForm(*pretty_sign.right(pretty_func))

        pretty_func.baseline = max_upper + sign_height//2
        pretty_func.binding = prettyForm.MUL
        return pretty_func

    def _print_Sum(self, expr):
        ascii_mode = not self._use_unicode

        def asum(hrequired, lower, upper, use_ascii):
            def adjust(s, wid=None, how='<^>'):
                if not wid or len(s) > wid:
                    return s
                need = wid - len(s)
                if how == '<^>' or how == "<" or how not in list('<^>'):
                    return s + ' '*need
                half = need//2
                lead = ' '*half
                if how == ">":
                    return " "*need + s
                return lead + s + ' '*(need - len(lead))

            h = max(hrequired, 2)
            d = h//2
            w = d + 1
            more = hrequired % 2

            lines = []
            if use_ascii:
                lines.append("_"*(w) + ' ')
                lines.append(r"\%s`" % (' '*(w - 1)))
                for i in range(1, d):
                    lines.append('%s\\%s' % (' '*i, ' '*(w - i)))
                if more:
                    lines.append('%s)%s' % (' '*(d), ' '*(w - d)))
                for i in reversed(range(1, d)):
                    lines.append('%s/%s' % (' '*i, ' '*(w - i)))
                lines.append("/" + "_"*(w - 1) + ',')
                return d, h + more, lines, 0
            else:
                w = w + more
                d = d + more
                vsum = vobj('sum', 4)
                lines.append("_"*(w))
                for i in range(0, d):
                    lines.append('%s%s%s' % (' '*i, vsum[2], ' '*(w - i - 1)))
                for i in reversed(range(0, d)):
                    lines.append('%s%s%s' % (' '*i, vsum[4], ' '*(w - i - 1)))
                lines.append(vsum[8]*(w))
                return d, h + 2*more, lines, more

        f = expr.function

        prettyF = self._print(f)

        if f.is_Add:  # add parens
            prettyF = prettyForm(*prettyF.parens())

        H = prettyF.height() + 2

        # \sum \sum \sum ...
        first = True
        max_upper = 0
        sign_height = 0

        for lim in expr.limits:
            if len(lim) == 3:
                prettyUpper = self._print(lim[2])
                prettyLower = self._print(Equality(lim[0], lim[1]))
            elif len(lim) == 2:
                prettyUpper = self._print("")
                prettyLower = self._print(Equality(lim[0], lim[1]))
            elif len(lim) == 1:
                prettyUpper = self._print("")
                prettyLower = self._print(lim[0])

            max_upper = max(max_upper, prettyUpper.height())

            # Create sum sign based on the height of the argument
            d, h, slines, adjustment = asum(
                H, prettyLower.width(), prettyUpper.width(), ascii_mode)
            prettySign = stringPict('')
            prettySign = prettyForm(*prettySign.stack(*slines))

            if first:
                sign_height = prettySign.height()

            prettySign = prettyForm(*prettySign.above(prettyUpper))
            prettySign = prettyForm(*prettySign.below(prettyLower))

            if first:
                # change F baseline so it centers on the sign
                prettyF.baseline -= d - (prettyF.height()//2 -
                                         prettyF.baseline) - adjustment
                first = False

            # put padding to the right
            pad = stringPict('')
            pad = prettyForm(*pad.stack(*[' ']*h))
            prettySign = prettyForm(*prettySign.right(pad))
            # put the present prettyF to the right
            prettyF = prettyForm(*prettySign.right(prettyF))

        prettyF.baseline = max_upper + sign_height//2
        prettyF.binding = prettyForm.MUL
        return prettyF

    def _print_Limit(self, l):
        e, z, z0, dir = l.args

        E = self._print(e)
        if precedence(e) <= PRECEDENCE["Mul"]:
            E = prettyForm(*E.parens('(', ')'))
        Lim = prettyForm('lim')

        LimArg = self._print(z)
        if self._use_unicode:
            LimArg = prettyForm(*LimArg.right(u'\N{BOX DRAWINGS LIGHT HORIZONTAL}\N{RIGHTWARDS ARROW}'))
        else:
            LimArg = prettyForm(*LimArg.right('->'))
        LimArg = prettyForm(*LimArg.right(self._print(z0)))

        if str(dir) == '+-' or z0 in (S.Infinity, S.NegativeInfinity):
            dir = ""
        else:
            if self._use_unicode:
                dir = u'\N{SUPERSCRIPT PLUS SIGN}' if str(dir) == "+" else u'\N{SUPERSCRIPT MINUS}'

        LimArg = prettyForm(*LimArg.right(self._print(dir)))

        Lim = prettyForm(*Lim.below(LimArg))
        Lim = prettyForm(*Lim.right(E), binding=prettyForm.MUL)

        return Lim

    def _print_matrix_contents(self, e):
        """
        This method factors out what is essentially grid printing.
        """
        M = e   # matrix
        Ms = {}  # i,j -> pretty(M[i,j])
        for i in range(M.rows):
            for j in range(M.cols):
                Ms[i, j] = self._print(M[i, j])

        # h- and v- spacers
        hsep = 2
        vsep = 1

        # max width for columns
        maxw = [-1] * M.cols

        for j in range(M.cols):
            maxw[j] = max([Ms[i, j].width() for i in range(M.rows)] or [0])

        # drawing result
        D = None

        for i in range(M.rows):

            D_row = None
            for j in range(M.cols):
                s = Ms[i, j]

                # reshape s to maxw
                # XXX this should be generalized, and go to stringPict.reshape ?
                assert s.width() <= maxw[j]

                # hcenter it, +0.5 to the right                        2
                # ( it's better to align formula starts for say 0 and r )
                # XXX this is not good in all cases -- maybe introduce vbaseline?
                wdelta = maxw[j] - s.width()
                wleft = wdelta // 2
                wright = wdelta - wleft

                s = prettyForm(*s.right(' '*wright))
                s = prettyForm(*s.left(' '*wleft))

                # we don't need vcenter cells -- this is automatically done in
                # a pretty way because when their baselines are taking into
                # account in .right()

                if D_row is None:
                    D_row = s   # first box in a row
                    continue

                D_row = prettyForm(*D_row.right(' '*hsep))  # h-spacer
                D_row = prettyForm(*D_row.right(s))

            if D is None:
                D = D_row       # first row in a picture
                continue

            # v-spacer
            for _ in range(vsep):
                D = prettyForm(*D.below(' '))

            D = prettyForm(*D.below(D_row))

        if D is None:
            D = prettyForm('')  # Empty Matrix

        return D

    def _print_MatrixBase(self, e):
        D = self._print_matrix_contents(e)
        D.baseline = D.height()//2
        D = prettyForm(*D.parens('[', ']'))
        return D
    _print_ImmutableMatrix = _print_MatrixBase
    _print_Matrix = _print_MatrixBase

    def _print_TensorProduct(self, expr):
        # This should somehow share the code with _print_WedgeProduct:
        circled_times = "\u2297"
        return self._print_seq(expr.args, None, None, circled_times,
            parenthesize=lambda x: precedence_traditional(x) <= PRECEDENCE["Mul"])

    def _print_WedgeProduct(self, expr):
        # This should somehow share the code with _print_TensorProduct:
        wedge_symbol = u"\u2227"
        return self._print_seq(expr.args, None, None, wedge_symbol,
            parenthesize=lambda x: precedence_traditional(x) <= PRECEDENCE["Mul"])

    def _print_Trace(self, e):
        D = self._print(e.arg)
        D = prettyForm(*D.parens('(',')'))
        D.baseline = D.height()//2
        D = prettyForm(*D.left('\n'*(0) + 'tr'))
        return D


    def _print_MatrixElement(self, expr):
        from sympy.matrices import MatrixSymbol
        from sympy import Symbol
        if (isinstance(expr.parent, MatrixSymbol)
                and expr.i.is_number and expr.j.is_number):
            return self._print(
                    Symbol(expr.parent.name + '_%d%d' % (expr.i, expr.j)))
        else:
            prettyFunc = self._print(expr.parent)
            prettyFunc = prettyForm(*prettyFunc.parens())
            prettyIndices = self._print_seq((expr.i, expr.j), delimiter=', '
                    ).parens(left='[', right=']')[0]
            pform = prettyForm(binding=prettyForm.FUNC,
                    *stringPict.next(prettyFunc, prettyIndices))

            # store pform parts so it can be reassembled e.g. when powered
            pform.prettyFunc = prettyFunc
            pform.prettyArgs = prettyIndices

            return pform


    def _print_MatrixSlice(self, m):
        # XXX works only for applied functions
        prettyFunc = self._print(m.parent)
        def ppslice(x):
            x = list(x)
            if x[2] == 1:
                del x[2]
            if x[1] == x[0] + 1:
                del x[1]
            if x[0] == 0:
                x[0] = ''
            return prettyForm(*self._print_seq(x, delimiter=':'))
        prettyArgs = self._print_seq((ppslice(m.rowslice),
            ppslice(m.colslice)), delimiter=', ').parens(left='[', right=']')[0]

        pform = prettyForm(
            binding=prettyForm.FUNC, *stringPict.next(prettyFunc, prettyArgs))

        # store pform parts so it can be reassembled e.g. when powered
        pform.prettyFunc = prettyFunc
        pform.prettyArgs = prettyArgs

        return pform

    def _print_Transpose(self, expr):
        pform = self._print(expr.arg)
        from sympy.matrices import MatrixSymbol
        if not isinstance(expr.arg, MatrixSymbol):
            pform = prettyForm(*pform.parens())
        pform = pform**(prettyForm('T'))
        return pform

    def _print_Adjoint(self, expr):
        pform = self._print(expr.arg)
        if self._use_unicode:
            dag = prettyForm(u'\N{DAGGER}')
        else:
            dag = prettyForm('+')
        from sympy.matrices import MatrixSymbol
        if not isinstance(expr.arg, MatrixSymbol):
            pform = prettyForm(*pform.parens())
        pform = pform**dag
        return pform

    def _print_BlockMatrix(self, B):
        if B.blocks.shape == (1, 1):
            return self._print(B.blocks[0, 0])
        return self._print(B.blocks)

    def _print_MatAdd(self, expr):
        s = None
        for item in expr.args:
            pform = self._print(item)
            if s is None:
                s = pform     # First element
            else:
                coeff = item.as_coeff_mmul()[0]
                if _coeff_isneg(S(coeff)):
                    s = prettyForm(*stringPict.next(s, ' '))
                    pform = self._print(item)
                else:
                    s = prettyForm(*stringPict.next(s, ' + '))
                s = prettyForm(*stringPict.next(s, pform))

        return s

    def _print_MatMul(self, expr):
        args = list(expr.args)
        from sympy import Add, MatAdd, HadamardProduct
        for i, a in enumerate(args):
            if (isinstance(a, (Add, MatAdd, HadamardProduct))
                    and len(expr.args) > 1):
                args[i] = prettyForm(*self._print(a).parens())
            else:
                args[i] = self._print(a)

        return prettyForm.__mul__(*args)

    def _print_DotProduct(self, expr):
        args = list(expr.args)

        for i, a in enumerate(args):
            args[i] = self._print(a)
        return prettyForm.__mul__(*args)

    def _print_MatPow(self, expr):
        pform = self._print(expr.base)
        from sympy.matrices import MatrixSymbol
        if not isinstance(expr.base, MatrixSymbol):
            pform = prettyForm(*pform.parens())
        pform = pform**(self._print(expr.exp))
        return pform

    def _print_HadamardProduct(self, expr):
        from sympy import MatAdd, MatMul
        if self._use_unicode:
            delim = pretty_atom('Ring')
        else:
            delim = '.*'
        return self._print_seq(expr.args, None, None, delim,
                parenthesize=lambda x: isinstance(x, (MatAdd, MatMul)))

    def _print_KroneckerProduct(self, expr):
        from sympy import MatAdd, MatMul
        if self._use_unicode:
            delim = u' \N{N-ARY CIRCLED TIMES OPERATOR} '
        else:
            delim = ' x '
        return self._print_seq(expr.args, None, None, delim,
                parenthesize=lambda x: isinstance(x, (MatAdd, MatMul)))

    _print_MatrixSymbol = _print_Symbol

    def _print_FunctionMatrix(self, X):
        D = self._print(X.lamda.expr)
        D = prettyForm(*D.parens('[', ']'))
        return D

    def _print_BasisDependent(self, expr):
        from sympy.vector import Vector

        if not self._use_unicode:
            raise NotImplementedError("ASCII pretty printing of BasisDependent is not implemented")

        if expr == expr.zero:
            return prettyForm(expr.zero._pretty_form)
        o1 = []
        vectstrs = []
        if isinstance(expr, Vector):
            items = expr.separate().items()
        else:
            items = [(0, expr)]
        for system, vect in items:
            inneritems = list(vect.components.items())
            inneritems.sort(key = lambda x: x[0].__str__())
            for k, v in inneritems:
                #if the coef of the basis vector is 1
                #we skip the 1
                if v == 1:
                    o1.append(u"" +
                              k._pretty_form)
                #Same for -1
                elif v == -1:
                    o1.append(u"(-1) " +
                              k._pretty_form)
                #For a general expr
                else:
                    #We always wrap the measure numbers in
                    #parentheses
                    arg_str = self._print(
                        v).parens()[0]

                    o1.append(arg_str + ' ' + k._pretty_form)
                vectstrs.append(k._pretty_form)

        #outstr = u("").join(o1)
        if o1[0].startswith(u" + "):
            o1[0] = o1[0][3:]
        elif o1[0].startswith(" "):
            o1[0] = o1[0][1:]
        #Fixing the newlines
        lengths = []
        strs = ['']
        flag = []
        for i, partstr in enumerate(o1):
            flag.append(0)
            # XXX: What is this hack?
            if '\n' in partstr:
                tempstr = partstr
                tempstr = tempstr.replace(vectstrs[i], '')
                if u'\N{right parenthesis extension}' in tempstr:   # If scalar is a fraction
                    for paren in range(len(tempstr)):
                        flag[i] = 1
                        if tempstr[paren] == u'\N{right parenthesis extension}':
                            tempstr = tempstr[:paren] + u'\N{right parenthesis extension}'\
                                         + ' '  + vectstrs[i] + tempstr[paren + 1:]
                            break
                elif u'\N{RIGHT PARENTHESIS LOWER HOOK}' in tempstr:
                    flag[i] = 1
                    tempstr = tempstr.replace(u'\N{RIGHT PARENTHESIS LOWER HOOK}',
                                        u'\N{RIGHT PARENTHESIS LOWER HOOK}'
                                        + ' ' + vectstrs[i])
                else:
                    tempstr = tempstr.replace(u'\N{RIGHT PARENTHESIS UPPER HOOK}',
                                        u'\N{RIGHT PARENTHESIS UPPER HOOK}'
                                        + ' ' + vectstrs[i])
                o1[i] = tempstr

        o1 = [x.split('\n') for x in o1]
        n_newlines = max([len(x) for x in o1])  # Width of part in its pretty form

        if 1 in flag:                           # If there was a fractional scalar
            for i, parts in enumerate(o1):
                if len(parts) == 1:             # If part has no newline
                    parts.insert(0, ' ' * (len(parts[0])))
                    flag[i] = 1

        for i, parts in enumerate(o1):
            lengths.append(len(parts[flag[i]]))
            for j in range(n_newlines):
                if j+1 <= len(parts):
                    if j >= len(strs):
                        strs.append(' ' * (sum(lengths[:-1]) +
                                           3*(len(lengths)-1)))
                    if j == flag[i]:
                        strs[flag[i]] += parts[flag[i]] + ' + '
                    else:
                        strs[j] += parts[j] + ' '*(lengths[-1] -
                                                   len(parts[j])+
                                                   3)
                else:
                    if j >= len(strs):
                        strs.append(' ' * (sum(lengths[:-1]) +
                                           3*(len(lengths)-1)))
                    strs[j] += ' '*(lengths[-1]+3)

        return prettyForm(u'\n'.join([s[:-3] for s in strs]))

    def _print_NDimArray(self, expr):
        from sympy import ImmutableMatrix

        if expr.rank() == 0:
            return self._print(expr[()])

        level_str = [[]] + [[] for i in range(expr.rank())]
        shape_ranges = [list(range(i)) for i in expr.shape]
        for outer_i in itertools.product(*shape_ranges):
            level_str[-1].append(expr[outer_i])
            even = True
            for back_outer_i in range(expr.rank()-1, -1, -1):
                if len(level_str[back_outer_i+1]) < expr.shape[back_outer_i]:
                    break
                if even:
                    level_str[back_outer_i].append(level_str[back_outer_i+1])
                else:
                    level_str[back_outer_i].append(ImmutableMatrix(level_str[back_outer_i+1]))
                    if len(level_str[back_outer_i + 1]) == 1:
                        level_str[back_outer_i][-1] = ImmutableMatrix([[level_str[back_outer_i][-1]]])
                even = not even
                level_str[back_outer_i+1] = []

        out_expr = level_str[0][0]
        if expr.rank() % 2 == 1:
            out_expr = ImmutableMatrix([out_expr])

        return self._print(out_expr)

    _print_ImmutableDenseNDimArray = _print_NDimArray
    _print_ImmutableSparseNDimArray = _print_NDimArray
    _print_MutableDenseNDimArray = _print_NDimArray
    _print_MutableSparseNDimArray = _print_NDimArray

    def _print_Piecewise(self, pexpr):

        P = {}
        for n, ec in enumerate(pexpr.args):
            P[n, 0] = self._print(ec.expr)
            if ec.cond == True:
                P[n, 1] = prettyForm('otherwise')
            else:
                P[n, 1] = prettyForm(
                    *prettyForm('for ').right(self._print(ec.cond)))
        hsep = 2
        vsep = 1
        len_args = len(pexpr.args)

        # max widths
        maxw = [max([P[i, j].width() for i in range(len_args)])
                for j in range(2)]

        # FIXME: Refactor this code and matrix into some tabular environment.
        # drawing result
        D = None

        for i in range(len_args):
            D_row = None
            for j in range(2):
                p = P[i, j]
                assert p.width() <= maxw[j]

                wdelta = maxw[j] - p.width()
                wleft = wdelta // 2
                wright = wdelta - wleft

                p = prettyForm(*p.right(' '*wright))
                p = prettyForm(*p.left(' '*wleft))

                if D_row is None:
                    D_row = p
                    continue

                D_row = prettyForm(*D_row.right(' '*hsep))  # h-spacer
                D_row = prettyForm(*D_row.right(p))
            if D is None:
                D = D_row       # first row in a picture
                continue

            # v-spacer
            for _ in range(vsep):
                D = prettyForm(*D.below(' '))

            D = prettyForm(*D.below(D_row))

        D = prettyForm(*D.parens('{', ''))
        D.baseline = D.height()//2
        D.binding = prettyForm.OPEN
        return D

    def _print_ITE(self, ite):
        from sympy.functions.elementary.piecewise import Piecewise
        return self._print(ite.rewrite(Piecewise))

    def _hprint_vec(self, v):
        D = None

        for a in v:
            p = a
            if D is None:
                D = p
            else:
                D = prettyForm(*D.right(', '))
                D = prettyForm(*D.right(p))
        if D is None:
            D = stringPict(' ')

        return D

    def _hprint_vseparator(self, p1, p2):
        tmp = prettyForm(*p1.right(p2))
        sep = stringPict(vobj('|', tmp.height()), baseline=tmp.baseline)
        return prettyForm(*p1.right(sep, p2))

    def _print_hyper(self, e):
        # FIXME refactor Matrix, Piecewise, and this into a tabular environment
        ap = [self._print(a) for a in e.ap]
        bq = [self._print(b) for b in e.bq]

        P = self._print(e.argument)
        P.baseline = P.height()//2

        # Drawing result - first create the ap, bq vectors
        D = None
        for v in [ap, bq]:
            D_row = self._hprint_vec(v)
            if D is None:
                D = D_row       # first row in a picture
            else:
                D = prettyForm(*D.below(' '))
                D = prettyForm(*D.below(D_row))

        # make sure that the argument `z' is centred vertically
        D.baseline = D.height()//2

        # insert horizontal separator
        P = prettyForm(*P.left(' '))
        D = prettyForm(*D.right(' '))

        # insert separating `|`
        D = self._hprint_vseparator(D, P)

        # add parens
        D = prettyForm(*D.parens('(', ')'))

        # create the F symbol
        above = D.height()//2 - 1
        below = D.height() - above - 1

        sz, t, b, add, img = annotated('F')
        F = prettyForm('\n' * (above - t) + img + '\n' * (below - b),
                       baseline=above + sz)
        add = (sz + 1)//2

        F = prettyForm(*F.left(self._print(len(e.ap))))
        F = prettyForm(*F.right(self._print(len(e.bq))))
        F.baseline = above + add

        D = prettyForm(*F.right(' ', D))

        return D

    def _print_meijerg(self, e):
        # FIXME refactor Matrix, Piecewise, and this into a tabular environment

        v = {}
        v[(0, 0)] = [self._print(a) for a in e.an]
        v[(0, 1)] = [self._print(a) for a in e.aother]
        v[(1, 0)] = [self._print(b) for b in e.bm]
        v[(1, 1)] = [self._print(b) for b in e.bother]

        P = self._print(e.argument)
        P.baseline = P.height()//2

        vp = {}
        for idx in v:
            vp[idx] = self._hprint_vec(v[idx])

        for i in range(2):
            maxw = max(vp[(0, i)].width(), vp[(1, i)].width())
            for j in range(2):
                s = vp[(j, i)]
                left = (maxw - s.width()) // 2
                right = maxw - left - s.width()
                s = prettyForm(*s.left(' ' * left))
                s = prettyForm(*s.right(' ' * right))
                vp[(j, i)] = s

        D1 = prettyForm(*vp[(0, 0)].right('  ', vp[(0, 1)]))
        D1 = prettyForm(*D1.below(' '))
        D2 = prettyForm(*vp[(1, 0)].right('  ', vp[(1, 1)]))
        D = prettyForm(*D1.below(D2))

        # make sure that the argument `z' is centred vertically
        D.baseline = D.height()//2

        # insert horizontal separator
        P = prettyForm(*P.left(' '))
        D = prettyForm(*D.right(' '))

        # insert separating `|`
        D = self._hprint_vseparator(D, P)

        # add parens
        D = prettyForm(*D.parens('(', ')'))

        # create the G symbol
        above = D.height()//2 - 1
        below = D.height() - above - 1

        sz, t, b, add, img = annotated('G')
        F = prettyForm('\n' * (above - t) + img + '\n' * (below - b),
                       baseline=above + sz)

        pp = self._print(len(e.ap))
        pq = self._print(len(e.bq))
        pm = self._print(len(e.bm))
        pn = self._print(len(e.an))

        def adjust(p1, p2):
            diff = p1.width() - p2.width()
            if diff == 0:
                return p1, p2
            elif diff > 0:
                return p1, prettyForm(*p2.left(' '*diff))
            else:
                return prettyForm(*p1.left(' '*-diff)), p2
        pp, pm = adjust(pp, pm)
        pq, pn = adjust(pq, pn)
        pu = prettyForm(*pm.right(', ', pn))
        pl = prettyForm(*pp.right(', ', pq))

        ht = F.baseline - above - 2
        if ht > 0:
            pu = prettyForm(*pu.below('\n'*ht))
        p = prettyForm(*pu.below(pl))

        F.baseline = above
        F = prettyForm(*F.right(p))

        F.baseline = above + add

        D = prettyForm(*F.right(' ', D))

        return D

    def _print_ExpBase(self, e):
        # TODO should exp_polar be printed differently?
        #      what about exp_polar(0), exp_polar(1)?
        base = prettyForm(pretty_atom('Exp1', 'e'))
        return base ** self._print(e.args[0])

    def _print_Function(self, e, sort=False, func_name=None):
        # optional argument func_name for supplying custom names
        # XXX works only for applied functions
        func = e.func
        args = e.args
        if sort:
            args = sorted(args, key=default_sort_key)

        if not func_name:
            func_name = func.__name__

        prettyFunc = self._print(Symbol(func_name))
        prettyArgs = prettyForm(*self._print_seq(args).parens())

        pform = prettyForm(
            binding=prettyForm.FUNC, *stringPict.next(prettyFunc, prettyArgs))

        # store pform parts so it can be reassembled e.g. when powered
        pform.prettyFunc = prettyFunc
        pform.prettyArgs = prettyArgs

        return pform

    @property
    def _special_function_classes(self):
        from sympy.functions.special.tensor_functions import KroneckerDelta
        from sympy.functions.special.gamma_functions import gamma, lowergamma
        from sympy.functions.special.beta_functions import beta
        from sympy.functions.special.delta_functions import DiracDelta
        from sympy.functions.special.error_functions import Chi
        return {KroneckerDelta: [greek_unicode['delta'], 'delta'],
                gamma: [greek_unicode['Gamma'], 'Gamma'],
                lowergamma: [greek_unicode['gamma'], 'gamma'],
                beta: [greek_unicode['Beta'], 'B'],
                DiracDelta: [greek_unicode['delta'], 'delta'],
                Chi: ['Chi', 'Chi']}

    def _print_FunctionClass(self, expr):
        for cls in self._special_function_classes:
            if issubclass(expr, cls) and expr.__name__ == cls.__name__:
                if self._use_unicode:
                    return prettyForm(self._special_function_classes[cls][0])
                else:
                    return prettyForm(self._special_function_classes[cls][1])
        func_name = expr.__name__
        return prettyForm(pretty_symbol(func_name))

    def _print_GeometryEntity(self, expr):
        # GeometryEntity is based on Tuple but should not print like a Tuple
        return self.emptyPrinter(expr)

    def _print_Lambda(self, e):
        vars, expr = e.args
        if self._use_unicode:
            arrow = u" \N{RIGHTWARDS ARROW FROM BAR} "
        else:
            arrow = " -> "
        if len(vars) == 1:
            var_form = self._print(vars[0])
        else:
            var_form = self._print(tuple(vars))

        return prettyForm(*stringPict.next(var_form, arrow, self._print(expr)), binding=8)

    def _print_Order(self, expr):
        pform = self._print(expr.expr)
        if (expr.point and any(p != S.Zero for p in expr.point)) or \
           len(expr.variables) > 1:
            pform = prettyForm(*pform.right("; "))
            if len(expr.variables) > 1:
                pform = prettyForm(*pform.right(self._print(expr.variables)))
            elif len(expr.variables):
                pform = prettyForm(*pform.right(self._print(expr.variables[0])))
            if self._use_unicode:
                pform = prettyForm(*pform.right(u" \N{RIGHTWARDS ARROW} "))
            else:
                pform = prettyForm(*pform.right(" -> "))
            if len(expr.point) > 1:
                pform = prettyForm(*pform.right(self._print(expr.point)))
            else:
                pform = prettyForm(*pform.right(self._print(expr.point[0])))
        pform = prettyForm(*pform.parens())
        pform = prettyForm(*pform.left("O"))
        return pform

    def _print_SingularityFunction(self, e):
        if self._use_unicode:
            shift = self._print(e.args[0]-e.args[1])
            n = self._print(e.args[2])
            base = prettyForm("<")
            base = prettyForm(*base.right(shift))
            base = prettyForm(*base.right(">"))
            pform = base**n
            return pform
        else:
            n = self._print(e.args[2])
            shift = self._print(e.args[0]-e.args[1])
            base = self._print_seq(shift, "<", ">", ' ')
            return base**n

    def _print_beta(self, e):
        func_name = greek_unicode['Beta'] if self._use_unicode else 'B'
        return self._print_Function(e, func_name=func_name)

    def _print_gamma(self, e):
        func_name = greek_unicode['Gamma'] if self._use_unicode else 'Gamma'
        return self._print_Function(e, func_name=func_name)

    def _print_uppergamma(self, e):
        func_name = greek_unicode['Gamma'] if self._use_unicode else 'Gamma'
        return self._print_Function(e, func_name=func_name)

    def _print_lowergamma(self, e):
        func_name = greek_unicode['gamma'] if self._use_unicode else 'lowergamma'
        return self._print_Function(e, func_name=func_name)

    def _print_DiracDelta(self, e):
        if self._use_unicode:
            if len(e.args) == 2:
                a = prettyForm(greek_unicode['delta'])
                b = self._print(e.args[1])
                b = prettyForm(*b.parens())
                c = self._print(e.args[0])
                c = prettyForm(*c.parens())
                pform = a**b
                pform = prettyForm(*pform.right(' '))
                pform = prettyForm(*pform.right(c))
                return pform
            pform = self._print(e.args[0])
            pform = prettyForm(*pform.parens())
            pform = prettyForm(*pform.left(greek_unicode['delta']))
            return pform
        else:
            return self._print_Function(e)

    def _print_expint(self, e):
        from sympy import Function
        if e.args[0].is_Integer and self._use_unicode:
            return self._print_Function(Function('E_%s' % e.args[0])(e.args[1]))
        return self._print_Function(e)

    def _print_Chi(self, e):
        # This needs a special case since otherwise it comes out as greek
        # letter chi...
        prettyFunc = prettyForm("Chi")
        prettyArgs = prettyForm(*self._print_seq(e.args).parens())

        pform = prettyForm(
            binding=prettyForm.FUNC, *stringPict.next(prettyFunc, prettyArgs))

        # store pform parts so it can be reassembled e.g. when powered
        pform.prettyFunc = prettyFunc
        pform.prettyArgs = prettyArgs

        return pform

    def _print_elliptic_e(self, e):
        pforma0 = self._print(e.args[0])
        if len(e.args) == 1:
            pform = pforma0
        else:
            pforma1 = self._print(e.args[1])
            pform = self._hprint_vseparator(pforma0, pforma1)
        pform = prettyForm(*pform.parens())
        pform = prettyForm(*pform.left('E'))
        return pform

    def _print_elliptic_k(self, e):
        pform = self._print(e.args[0])
        pform = prettyForm(*pform.parens())
        pform = prettyForm(*pform.left('K'))
        return pform

    def _print_elliptic_f(self, e):
        pforma0 = self._print(e.args[0])
        pforma1 = self._print(e.args[1])
        pform = self._hprint_vseparator(pforma0, pforma1)
        pform = prettyForm(*pform.parens())
        pform = prettyForm(*pform.left('F'))
        return pform

    def _print_elliptic_pi(self, e):
        name = greek_unicode['Pi'] if self._use_unicode else 'Pi'
        pforma0 = self._print(e.args[0])
        pforma1 = self._print(e.args[1])
        if len(e.args) == 2:
            pform = self._hprint_vseparator(pforma0, pforma1)
        else:
            pforma2 = self._print(e.args[2])
            pforma = self._hprint_vseparator(pforma1, pforma2)
            pforma = prettyForm(*pforma.left('; '))
            pform = prettyForm(*pforma.left(pforma0))
        pform = prettyForm(*pform.parens())
        pform = prettyForm(*pform.left(name))
        return pform

    def _print_GoldenRatio(self, expr):
        if self._use_unicode:
            return prettyForm(pretty_symbol('phi'))
        return self._print(Symbol("GoldenRatio"))

    def _print_EulerGamma(self, expr):
        if self._use_unicode:
            return prettyForm(pretty_symbol('gamma'))
        return self._print(Symbol("EulerGamma"))

    def _print_Mod(self, expr):
        pform = self._print(expr.args[0])
        if pform.binding > prettyForm.MUL:
            pform = prettyForm(*pform.parens())
        pform = prettyForm(*pform.right(' mod '))
        pform = prettyForm(*pform.right(self._print(expr.args[1])))
        pform.binding = prettyForm.OPEN
        return pform

    def _print_Add(self, expr, order=None):
        if self.order == 'none':
            terms = list(expr.args)
        else:
            terms = self._as_ordered_terms(expr, order=order)
        pforms, indices = [], []

        def pretty_negative(pform, index):
            """Prepend a minus sign to a pretty form. """
            #TODO: Move this code to prettyForm
            if index == 0:
                if pform.height() > 1:
                    pform_neg = '- '
                else:
                    pform_neg = '-'
            else:
                pform_neg = ' - '

            if (pform.binding > prettyForm.NEG
                or pform.binding == prettyForm.ADD):
                p = stringPict(*pform.parens())
            else:
                p = pform
            p = stringPict.next(pform_neg, p)
            # Lower the binding to NEG, even if it was higher. Otherwise, it
            # will print as a + ( - (b)), instead of a - (b).
            return prettyForm(binding=prettyForm.NEG, *p)

        for i, term in enumerate(terms):
            if term.is_Mul and _coeff_isneg(term):
                coeff, other = term.as_coeff_mul(rational=False)
                pform = self._print(Mul(-coeff, *other, evaluate=False))
                pforms.append(pretty_negative(pform, i))
            elif term.is_Rational and term.q > 1:
                pforms.append(None)
                indices.append(i)
            elif term.is_Number and term < 0:
                pform = self._print(-term)
                pforms.append(pretty_negative(pform, i))
            elif term.is_Relational:
                pforms.append(prettyForm(*self._print(term).parens()))
            else:
                pforms.append(self._print(term))

        if indices:
            large = True

            for pform in pforms:
                if pform is not None and pform.height() > 1:
                    break
            else:
                large = False

            for i in indices:
                term, negative = terms[i], False

                if term < 0:
                    term, negative = -term, True

                if large:
                    pform = prettyForm(str(term.p))/prettyForm(str(term.q))
                else:
                    pform = self._print(term)

                if negative:
                    pform = pretty_negative(pform, i)

                pforms[i] = pform

        return prettyForm.__add__(*pforms)

    def _print_Mul(self, product):
        from sympy.physics.units import Quantity
        a = []  # items in the numerator
        b = []  # items that are in the denominator (if any)

        if self.order not in ('old', 'none'):
            args = product.as_ordered_factors()
        else:
            args = list(product.args)

        # If quantities are present append them at the back
        args = sorted(args, key=lambda x: isinstance(x, Quantity) or
                     (isinstance(x, Pow) and isinstance(x.base, Quantity)))

        # Gather terms for numerator/denominator
        for item in args:
            if item.is_commutative and item.is_Pow and item.exp.is_Rational and item.exp.is_negative:
                if item.exp != -1:
                    b.append(Pow(item.base, -item.exp, evaluate=False))
                else:
                    b.append(Pow(item.base, -item.exp))
            elif item.is_Rational and item is not S.Infinity:
                if item.p != 1:
                    a.append( Rational(item.p) )
                if item.q != 1:
                    b.append( Rational(item.q) )
            else:
                a.append(item)

        from sympy import Integral, Piecewise, Product, Sum

        # Convert to pretty forms. Add parens to Add instances if there
        # is more than one term in the numer/denom
        for i in range(0, len(a)):
            if (a[i].is_Add and len(a) > 1) or (i != len(a) - 1 and
                    isinstance(a[i], (Integral, Piecewise, Product, Sum))):
                a[i] = prettyForm(*self._print(a[i]).parens())
            elif a[i].is_Relational:
                a[i] = prettyForm(*self._print(a[i]).parens())
            else:
                a[i] = self._print(a[i])

        for i in range(0, len(b)):
            if (b[i].is_Add and len(b) > 1) or (i != len(b) - 1 and
                    isinstance(b[i], (Integral, Piecewise, Product, Sum))):
                b[i] = prettyForm(*self._print(b[i]).parens())
            else:
                b[i] = self._print(b[i])

        # Construct a pretty form
        if len(b) == 0:
            return prettyForm.__mul__(*a)
        else:
            if len(a) == 0:
                a.append( self._print(S.One) )
            return prettyForm.__mul__(*a)/prettyForm.__mul__(*b)

    # A helper function for _print_Pow to print x**(1/n)
    def _print_nth_root(self, base, expt):
        bpretty = self._print(base)

        # In very simple cases, use a single-char root sign
        if (self._settings['use_unicode_sqrt_char'] and self._use_unicode
            and expt is S.Half and bpretty.height() == 1
            and (bpretty.width() == 1
                 or (base.is_Integer and base.is_nonnegative))):
            return prettyForm(*bpretty.left(u'\N{SQUARE ROOT}'))

        # Construct root sign, start with the \/ shape
        _zZ = xobj('/', 1)
        rootsign = xobj('\\', 1) + _zZ
        # Make exponent number to put above it
        if isinstance(expt, Rational):
            exp = str(expt.q)
            if exp == '2':
                exp = ''
        else:
            exp = str(expt.args[0])
        exp = exp.ljust(2)
        if len(exp) > 2:
            rootsign = ' '*(len(exp) - 2) + rootsign
        # Stack the exponent
        rootsign = stringPict(exp + '\n' + rootsign)
        rootsign.baseline = 0
        # Diagonal: length is one less than height of base
        linelength = bpretty.height() - 1
        diagonal = stringPict('\n'.join(
            ' '*(linelength - i - 1) + _zZ + ' '*i
            for i in range(linelength)
        ))
        # Put baseline just below lowest line: next to exp
        diagonal.baseline = linelength - 1
        # Make the root symbol
        rootsign = prettyForm(*rootsign.right(diagonal))
        # Det the baseline to match contents to fix the height
        # but if the height of bpretty is one, the rootsign must be one higher
        rootsign.baseline = max(1, bpretty.baseline)
        #build result
        s = prettyForm(hobj('_', 2 + bpretty.width()))
        s = prettyForm(*bpretty.above(s))
        s = prettyForm(*s.left(rootsign))
        return s

    def _print_Pow(self, power):
        from sympy.simplify.simplify import fraction
        b, e = power.as_base_exp()
        if power.is_commutative:
            if e is S.NegativeOne:
                return prettyForm("1")/self._print(b)
            n, d = fraction(e)
            if n is S.One and d.is_Atom and not e.is_Integer:
                return self._print_nth_root(b, e)
            if e.is_Rational and e < 0:
                return prettyForm("1")/self._print(Pow(b, -e, evaluate=False))

        if b.is_Relational:
            return prettyForm(*self._print(b).parens()).__pow__(self._print(e))

        return self._print(b)**self._print(e)

    def _print_UnevaluatedExpr(self, expr):
        return self._print(expr.args[0])

    def __print_numer_denom(self, p, q):
        if q == 1:
            if p < 0:
                return prettyForm(str(p), binding=prettyForm.NEG)
            else:
                return prettyForm(str(p))
        elif abs(p) >= 10 and abs(q) >= 10:
            # If more than one digit in numer and denom, print larger fraction
            if p < 0:
                return prettyForm(str(p), binding=prettyForm.NEG)/prettyForm(str(q))
                # Old printing method:
                #pform = prettyForm(str(-p))/prettyForm(str(q))
                #return prettyForm(binding=prettyForm.NEG, *pform.left('- '))
            else:
                return prettyForm(str(p))/prettyForm(str(q))
        else:
            return None

    def _print_Rational(self, expr):
        result = self.__print_numer_denom(expr.p, expr.q)

        if result is not None:
            return result
        else:
            return self.emptyPrinter(expr)

    def _print_Fraction(self, expr):
        result = self.__print_numer_denom(expr.numerator, expr.denominator)

        if result is not None:
            return result
        else:
            return self.emptyPrinter(expr)

    def _print_ProductSet(self, p):
        if len(p.sets) > 1 and not has_variety(p.sets):
            from sympy import Pow
            return self._print(Pow(p.sets[0], len(p.sets), evaluate=False))
        else:
            prod_char = u"\N{MULTIPLICATION SIGN}" if self._use_unicode else 'x'
            return self._print_seq(p.sets, None, None, ' %s ' % prod_char,
                                   parenthesize=lambda set: set.is_Union or
                                   set.is_Intersection or set.is_ProductSet)

    def _print_FiniteSet(self, s):
        items = sorted(s.args, key=default_sort_key)
        return self._print_seq(items, '{', '}', ', ' )

    def _print_Range(self, s):

        if self._use_unicode:
            dots = u"\N{HORIZONTAL ELLIPSIS}"
        else:
            dots = '...'

        if s.start.is_infinite:
            printset = s.start, dots, s[-1] - s.step, s[-1]
        elif s.stop.is_infinite or len(s) > 4:
            it = iter(s)
            printset = next(it), next(it), dots, s[-1]
        else:
            printset = tuple(s)

        return self._print_seq(printset, '{', '}', ', ' )

    def _print_Interval(self, i):
        if i.start == i.end:
            return self._print_seq(i.args[:1], '{', '}')

        else:
            if i.left_open:
                left = '('
            else:
                left = '['

            if i.right_open:
                right = ')'
            else:
                right = ']'

            return self._print_seq(i.args[:2], left, right)

    def _print_AccumulationBounds(self, i):
        left = '<'
        right = '>'

        return self._print_seq(i.args[:2], left, right)

    def _print_Intersection(self, u):

        delimiter = ' %s ' % pretty_atom('Intersection', 'n')

        return self._print_seq(u.args, None, None, delimiter,
                               parenthesize=lambda set: set.is_ProductSet or
                               set.is_Union or set.is_Complement)

    def _print_Union(self, u):

        union_delimiter = ' %s ' % pretty_atom('Union', 'U')

        return self._print_seq(u.args, None, None, union_delimiter,
                               parenthesize=lambda set: set.is_ProductSet or
                               set.is_Intersection or set.is_Complement)

    def _print_SymmetricDifference(self, u):
        if not self._use_unicode:
            raise NotImplementedError("ASCII pretty printing of SymmetricDifference is not implemented")

        sym_delimeter = ' %s ' % pretty_atom('SymmetricDifference')

        return self._print_seq(u.args, None, None, sym_delimeter)

    def _print_Complement(self, u):

        delimiter = r' \ '

        return self._print_seq(u.args, None, None, delimiter,
             parenthesize=lambda set: set.is_ProductSet or set.is_Intersection
                               or set.is_Union)

    def _print_ImageSet(self, ts):
        if self._use_unicode:
            inn = u"\N{SMALL ELEMENT OF}"
        else:
            inn = 'in'
        variables = ts.lamda.variables
        expr = self._print(ts.lamda.expr)
        bar = self._print("|")
        sets = [self._print(i) for i in ts.args[1:]]
        if len(sets) == 1:
            return self._print_seq((expr, bar, variables[0], inn, sets[0]), "{", "}", ' ')
        else:
            pargs = tuple(j for var, setv in zip(variables, sets) for j in (var, inn, setv, ","))
            return self._print_seq((expr, bar) + pargs[:-1], "{", "}", ' ')

    def _print_ConditionSet(self, ts):
        if self._use_unicode:
            inn = u"\N{SMALL ELEMENT OF}"
            # using _and because and is a keyword and it is bad practice to
            # overwrite them
            _and = u"\N{LOGICAL AND}"
        else:
            inn = 'in'
            _and = 'and'

        variables = self._print_seq(Tuple(ts.sym))
        try:
            cond = self._print(ts.condition.as_expr())
        except AttributeError:
            cond = self._print(ts.condition)
            if self._use_unicode:
                cond = self._print_seq(cond, "(", ")")

        bar = self._print("|")

        if ts.base_set is S.UniversalSet:
            return self._print_seq((variables, bar, cond), "{", "}", ' ')

        base = self._print(ts.base_set)
        return self._print_seq((variables, bar, variables, inn,
                                base, _and, cond), "{", "}", ' ')

    def _print_ComplexRegion(self, ts):
        if self._use_unicode:
            inn = u"\N{SMALL ELEMENT OF}"
        else:
            inn = 'in'
        variables = self._print_seq(ts.variables)
        expr = self._print(ts.expr)
        bar = self._print("|")
        prodsets = self._print(ts.sets)

        return self._print_seq((expr, bar, variables, inn, prodsets), "{", "}", ' ')

    def _print_Contains(self, e):
        var, set = e.args
        if self._use_unicode:
            el = u" \N{ELEMENT OF} "
            return prettyForm(*stringPict.next(self._print(var),
                                               el, self._print(set)), binding=8)
        else:
            return prettyForm(sstr(e))

    def _print_FourierSeries(self, s):
        if self._use_unicode:
            dots = u"\N{HORIZONTAL ELLIPSIS}"
        else:
            dots = '...'
        return self._print_Add(s.truncate()) + self._print(dots)

    def _print_FormalPowerSeries(self, s):
        return self._print_Add(s.infinite)

    def _print_SetExpr(self, se):
        pretty_set = prettyForm(*self._print(se.set).parens())
        pretty_name = self._print(Symbol("SetExpr"))
        return prettyForm(*pretty_name.right(pretty_set))

    def _print_SeqFormula(self, s):
        if self._use_unicode:
            dots = u"\N{HORIZONTAL ELLIPSIS}"
        else:
            dots = '...'

        if s.start is S.NegativeInfinity:
            stop = s.stop
            printset = (dots, s.coeff(stop - 3), s.coeff(stop - 2),
                s.coeff(stop - 1), s.coeff(stop))
        elif s.stop is S.Infinity or s.length > 4:
            printset = s[:4]
            printset.append(dots)
            printset = tuple(printset)
        else:
            printset = tuple(s)
        return self._print_list(printset)

    _print_SeqPer = _print_SeqFormula
    _print_SeqAdd = _print_SeqFormula
    _print_SeqMul = _print_SeqFormula

    def _print_seq(self, seq, left=None, right=None, delimiter=', ',
            parenthesize=lambda x: False):
        s = None

        for item in seq:
            pform = self._print(item)

            if parenthesize(item):
                pform = prettyForm(*pform.parens())
            if s is None:
                # first element
                s = pform
            else:
                s = prettyForm(*stringPict.next(s, delimiter))
                s = prettyForm(*stringPict.next(s, pform))

        if s is None:
            s = stringPict('')

        s = prettyForm(*s.parens(left, right, ifascii_nougly=True))
        return s

    def join(self, delimiter, args):
        pform = None

        for arg in args:
            if pform is None:
                pform = arg
            else:
                pform = prettyForm(*pform.right(delimiter))
                pform = prettyForm(*pform.right(arg))

        if pform is None:
            return prettyForm("")
        else:
            return pform

    def _print_list(self, l):
        return self._print_seq(l, '[', ']')

    def _print_tuple(self, t):
        if len(t) == 1:
            ptuple = prettyForm(*stringPict.next(self._print(t[0]), ','))
            return prettyForm(*ptuple.parens('(', ')', ifascii_nougly=True))
        else:
            return self._print_seq(t, '(', ')')

    def _print_Tuple(self, expr):
        return self._print_tuple(expr)

    def _print_dict(self, d):
        keys = sorted(d.keys(), key=default_sort_key)
        items = []

        for k in keys:
            K = self._print(k)
            V = self._print(d[k])
            s = prettyForm(*stringPict.next(K, ': ', V))

            items.append(s)

        return self._print_seq(items, '{', '}')

    def _print_Dict(self, d):
        return self._print_dict(d)

    def _print_set(self, s):
        if not s:
            return prettyForm('set()')
        items = sorted(s, key=default_sort_key)
        pretty = self._print_seq(items)
        pretty = prettyForm(*pretty.parens('{', '}', ifascii_nougly=True))
        return pretty

    def _print_frozenset(self, s):
        if not s:
            return prettyForm('frozenset()')
        items = sorted(s, key=default_sort_key)
        pretty = self._print_seq(items)
        pretty = prettyForm(*pretty.parens('{', '}', ifascii_nougly=True))
        pretty = prettyForm(*pretty.parens('(', ')', ifascii_nougly=True))
        pretty = prettyForm(*stringPict.next(type(s).__name__, pretty))
        return pretty

    def _print_PolyRing(self, ring):
        return prettyForm(sstr(ring))

    def _print_FracField(self, field):
        return prettyForm(sstr(field))

    def _print_FreeGroupElement(self, elm):
        return prettyForm(str(elm))

    def _print_PolyElement(self, poly):
        return prettyForm(sstr(poly))

    def _print_FracElement(self, frac):
        return prettyForm(sstr(frac))

    def _print_AlgebraicNumber(self, expr):
        if expr.is_aliased:
            return self._print(expr.as_poly().as_expr())
        else:
            return self._print(expr.as_expr())

    def _print_ComplexRootOf(self, expr):
        args = [self._print_Add(expr.expr, order='lex'), expr.index]
        pform = prettyForm(*self._print_seq(args).parens())
        pform = prettyForm(*pform.left('CRootOf'))
        return pform

    def _print_RootSum(self, expr):
        args = [self._print_Add(expr.expr, order='lex')]

        if expr.fun is not S.IdentityFunction:
            args.append(self._print(expr.fun))

        pform = prettyForm(*self._print_seq(args).parens())
        pform = prettyForm(*pform.left('RootSum'))

        return pform

    def _print_FiniteField(self, expr):
        if self._use_unicode:
            form = u'\N{DOUBLE-STRUCK CAPITAL Z}_%d'
        else:
            form = 'GF(%d)'

        return prettyForm(pretty_symbol(form % expr.mod))

    def _print_IntegerRing(self, expr):
        if self._use_unicode:
            return prettyForm(u'\N{DOUBLE-STRUCK CAPITAL Z}')
        else:
            return prettyForm('ZZ')

    def _print_RationalField(self, expr):
        if self._use_unicode:
            return prettyForm(u'\N{DOUBLE-STRUCK CAPITAL Q}')
        else:
            return prettyForm('QQ')

    def _print_RealField(self, domain):
        if self._use_unicode:
            prefix = u'\N{DOUBLE-STRUCK CAPITAL R}'
        else:
            prefix = 'RR'

        if domain.has_default_precision:
            return prettyForm(prefix)
        else:
            return self._print(pretty_symbol(prefix + "_" + str(domain.precision)))

    def _print_ComplexField(self, domain):
        if self._use_unicode:
            prefix = u'\N{DOUBLE-STRUCK CAPITAL C}'
        else:
            prefix = 'CC'

        if domain.has_default_precision:
            return prettyForm(prefix)
        else:
            return self._print(pretty_symbol(prefix + "_" + str(domain.precision)))

    def _print_PolynomialRing(self, expr):
        args = list(expr.symbols)

        if not expr.order.is_default:
            order = prettyForm(*prettyForm("order=").right(self._print(expr.order)))
            args.append(order)

        pform = self._print_seq(args, '[', ']')
        pform = prettyForm(*pform.left(self._print(expr.domain)))

        return pform

    def _print_FractionField(self, expr):
        args = list(expr.symbols)

        if not expr.order.is_default:
            order = prettyForm(*prettyForm("order=").right(self._print(expr.order)))
            args.append(order)

        pform = self._print_seq(args, '(', ')')
        pform = prettyForm(*pform.left(self._print(expr.domain)))

        return pform

    def _print_PolynomialRingBase(self, expr):
        g = expr.symbols
        if str(expr.order) != str(expr.default_order):
            g = g + ("order=" + str(expr.order),)
        pform = self._print_seq(g, '[', ']')
        pform = prettyForm(*pform.left(self._print(expr.domain)))

        return pform

    def _print_GroebnerBasis(self, basis):
        exprs = [ self._print_Add(arg, order=basis.order)
                  for arg in basis.exprs ]
        exprs = prettyForm(*self.join(", ", exprs).parens(left="[", right="]"))

        gens = [ self._print(gen) for gen in basis.gens ]

        domain = prettyForm(
            *prettyForm("domain=").right(self._print(basis.domain)))
        order = prettyForm(
            *prettyForm("order=").right(self._print(basis.order)))

        pform = self.join(", ", [exprs] + gens + [domain, order])

        pform = prettyForm(*pform.parens())
        pform = prettyForm(*pform.left(basis.__class__.__name__))

        return pform

    def _print_Subs(self, e):
        pform = self._print(e.expr)
        pform = prettyForm(*pform.parens())

        h = pform.height() if pform.height() > 1 else 2
        rvert = stringPict(vobj('|', h), baseline=pform.baseline)
        pform = prettyForm(*pform.right(rvert))

        b = pform.baseline
        pform.baseline = pform.height() - 1
        pform = prettyForm(*pform.right(self._print_seq([
            self._print_seq((self._print(v[0]), xsym('=='), self._print(v[1])),
                delimiter='') for v in zip(e.variables, e.point) ])))

        pform.baseline = b
        return pform

    def _print_euler(self, e):
        pform = prettyForm("E")
        arg = self._print(e.args[0])
        pform_arg = prettyForm(" "*arg.width())
        pform_arg = prettyForm(*pform_arg.below(arg))
        pform = prettyForm(*pform.right(pform_arg))
        if len(e.args) == 1:
            return pform
        m, x = e.args
        # TODO: copy-pasted from _print_Function: can we do better?
        prettyFunc = pform
        prettyArgs = prettyForm(*self._print_seq([x]).parens())
        pform = prettyForm(
            binding=prettyForm.FUNC, *stringPict.next(prettyFunc, prettyArgs))
        pform.prettyFunc = prettyFunc
        pform.prettyArgs = prettyArgs
        return pform

    def _print_catalan(self, e):
        pform = prettyForm("C")
        arg = self._print(e.args[0])
        pform_arg = prettyForm(" "*arg.width())
        pform_arg = prettyForm(*pform_arg.below(arg))
        pform = prettyForm(*pform.right(pform_arg))
        return pform

    def _print_KroneckerDelta(self, e):
        pform = self._print(e.args[0])
        pform = prettyForm(*pform.right((prettyForm(','))))
        pform = prettyForm(*pform.right((self._print(e.args[1]))))
        if self._use_unicode:
            a = stringPict(pretty_symbol('delta'))
        else:
            a = stringPict('d')
        b = pform
        top = stringPict(*b.left(' '*a.width()))
        bot = stringPict(*a.right(' '*b.width()))
        return prettyForm(binding=prettyForm.POW, *bot.below(top))

    def _print_RandomDomain(self, d):
        if hasattr(d, 'as_boolean'):
            pform = self._print('Domain: ')
            pform = prettyForm(*pform.right(self._print(d.as_boolean())))
            return pform
        elif hasattr(d, 'set'):
            pform = self._print('Domain: ')
            pform = prettyForm(*pform.right(self._print(d.symbols)))
            pform = prettyForm(*pform.right(self._print(' in ')))
            pform = prettyForm(*pform.right(self._print(d.set)))
            return pform
        elif hasattr(d, 'symbols'):
            pform = self._print('Domain on ')
            pform = prettyForm(*pform.right(self._print(d.symbols)))
            return pform
        else:
            return self._print(None)

    def _print_DMP(self, p):
        try:
            if p.ring is not None:
                # TODO incorporate order
                return self._print(p.ring.to_sympy(p))
        except SympifyError:
            pass
        return self._print(repr(p))

    def _print_DMF(self, p):
        return self._print_DMP(p)

    def _print_Object(self, object):
        return self._print(pretty_symbol(object.name))

    def _print_Morphism(self, morphism):
        arrow = xsym("-->")

        domain = self._print(morphism.domain)
        codomain = self._print(morphism.codomain)
        tail = domain.right(arrow, codomain)[0]

        return prettyForm(tail)

    def _print_NamedMorphism(self, morphism):
        pretty_name = self._print(pretty_symbol(morphism.name))
        pretty_morphism = self._print_Morphism(morphism)
        return prettyForm(pretty_name.right(":", pretty_morphism)[0])

    def _print_IdentityMorphism(self, morphism):
        from sympy.categories import NamedMorphism
        return self._print_NamedMorphism(
            NamedMorphism(morphism.domain, morphism.codomain, "id"))

    def _print_CompositeMorphism(self, morphism):

        circle = xsym(".")

        # All components of the morphism have names and it is thus
        # possible to build the name of the composite.
        component_names_list = [pretty_symbol(component.name) for
                                component in morphism.components]
        component_names_list.reverse()
        component_names = circle.join(component_names_list) + ":"

        pretty_name = self._print(component_names)
        pretty_morphism = self._print_Morphism(morphism)
        return prettyForm(pretty_name.right(pretty_morphism)[0])

    def _print_Category(self, category):
        return self._print(pretty_symbol(category.name))

    def _print_Diagram(self, diagram):
        if not diagram.premises:
            # This is an empty diagram.
            return self._print(S.EmptySet)

        pretty_result = self._print(diagram.premises)
        if diagram.conclusions:
            results_arrow = " %s " % xsym("==>")

            pretty_conclusions = self._print(diagram.conclusions)[0]
            pretty_result = pretty_result.right(
                results_arrow, pretty_conclusions)

        return prettyForm(pretty_result[0])

    def _print_DiagramGrid(self, grid):
        from sympy.matrices import Matrix
        from sympy import Symbol
        matrix = Matrix([[grid[i, j] if grid[i, j] else Symbol(" ")
                          for j in range(grid.width)]
                         for i in range(grid.height)])
        return self._print_matrix_contents(matrix)

    def _print_FreeModuleElement(self, m):
        # Print as row vector for convenience, for now.
        return self._print_seq(m, '[', ']')

    def _print_SubModule(self, M):
        return self._print_seq(M.gens, '<', '>')

    def _print_FreeModule(self, M):
        return self._print(M.ring)**self._print(M.rank)

    def _print_ModuleImplementedIdeal(self, M):
        return self._print_seq([x for [x] in M._module.gens], '<', '>')

    def _print_QuotientRing(self, R):
        return self._print(R.ring) / self._print(R.base_ideal)

    def _print_QuotientRingElement(self, R):
        return self._print(R.data) + self._print(R.ring.base_ideal)

    def _print_QuotientModuleElement(self, m):
        return self._print(m.data) + self._print(m.module.killed_module)

    def _print_QuotientModule(self, M):
        return self._print(M.base) / self._print(M.killed_module)

    def _print_MatrixHomomorphism(self, h):
        matrix = self._print(h._sympy_matrix())
        matrix.baseline = matrix.height() // 2
        pform = prettyForm(*matrix.right(' : ', self._print(h.domain),
            ' %s> ' % hobj('-', 2), self._print(h.codomain)))
        return pform

    def _print_BaseScalarField(self, field):
        string = field._coord_sys._names[field._index]
        return self._print(pretty_symbol(string))

    def _print_BaseVectorField(self, field):
        s = U('PARTIAL DIFFERENTIAL') + '_' + field._coord_sys._names[field._index]
        return self._print(pretty_symbol(s))

    def _print_Differential(self, diff):
        field = diff._form_field
        if hasattr(field, '_coord_sys'):
            string = field._coord_sys._names[field._index]
            return self._print(u'\N{DOUBLE-STRUCK ITALIC SMALL D} ' + pretty_symbol(string))
        else:
            pform = self._print(field)
            pform = prettyForm(*pform.parens())
            return prettyForm(*pform.left(u"\N{DOUBLE-STRUCK ITALIC SMALL D}"))

    def _print_Tr(self, p):
        #TODO: Handle indices
        pform = self._print(p.args[0])
        pform = prettyForm(*pform.left('%s(' % (p.__class__.__name__)))
        pform = prettyForm(*pform.right(')'))
        return pform

    def _print_primenu(self, e):
        pform = self._print(e.args[0])
        pform = prettyForm(*pform.parens())
        if self._use_unicode:
            pform = prettyForm(*pform.left(greek_unicode['nu']))
        else:
            pform = prettyForm(*pform.left('nu'))
        return pform

    def _print_primeomega(self, e):
        pform = self._print(e.args[0])
        pform = prettyForm(*pform.parens())
        if self._use_unicode:
            pform = prettyForm(*pform.left(greek_unicode['Omega']))
        else:
            pform = prettyForm(*pform.left('Omega'))
        return pform

    def _print_Quantity(self, e):
        if e.name.name == 'degree':
            pform = self._print(u"\N{DEGREE SIGN}")
            return pform
        else:
            return self.emptyPrinter(e)


def pretty(expr, **settings):
    """Returns a string containing the prettified form of expr.

    For information on keyword arguments see pretty_print function.

    """
    pp = PrettyPrinter(settings)

    # XXX: this is an ugly hack, but at least it works
    use_unicode = pp._settings['use_unicode']
    uflag = pretty_use_unicode(use_unicode)

    try:
        return pp.doprint(expr)
    finally:
        pretty_use_unicode(uflag)


def pretty_print(expr, wrap_line=True, num_columns=None, use_unicode=None,
                 full_prec="auto", order=None, use_unicode_sqrt_char=True):
    """Prints expr in pretty form.

    pprint is just a shortcut for this function.

    Parameters
    ==========

    expr : expression
        The expression to print.

    wrap_line : bool, optional (default=True)
        Line wrapping enabled/disabled.

    num_columns : int or None, optional (default=None)
        Number of columns before line breaking (default to None which reads
        the terminal width), useful when using SymPy without terminal.

    use_unicode : bool or None, optional (default=None)
        Use unicode characters, such as the Greek letter pi instead of
        the string pi.

    full_prec : bool or string, optional (default="auto")
        Use full precision.

    order : bool or string, optional (default=None)
        Set to 'none' for long expressions if slow; default is None.

    use_unicode_sqrt_char : bool, optional (default=True)
        Use compact single-character square root symbol (when unambiguous).

    """
    print(pretty(expr, wrap_line=wrap_line, num_columns=num_columns,
                 use_unicode=use_unicode, full_prec=full_prec, order=order,
                 use_unicode_sqrt_char=use_unicode_sqrt_char))

pprint = pretty_print


def pager_print(expr, **settings):
    """Prints expr using the pager, in pretty form.

    This invokes a pager command using pydoc. Lines are not wrapped
    automatically. This routine is meant to be used with a pager that allows
    sideways scrolling, like ``less -S``.

    Parameters are the same as for ``pretty_print``. If you wish to wrap lines,
    pass ``num_columns=None`` to auto-detect the width of the terminal.

    """
    from pydoc import pager
    from locale import getpreferredencoding
    if 'num_columns' not in settings:
        settings['num_columns'] = 500000  # disable line wrap
    pager(pretty(expr, **settings).encode(getpreferredencoding()))
