maxima.py

r"""
Pexpect interface to Maxima

Maxima is a free GPL'd general purpose computer algebra system
whose development started in 1968 at MIT. It contains symbolic
manipulation algorithms, as well as implementations of special
functions, including elliptic functions and generalized
hypergeometric functions. Moreover, Maxima has implementations of
many functions relating to the invariant theory of the symmetric
group `S_n`. (However, the commands for group invariants,
and the corresponding Maxima documentation, are in French.) For many
links to Maxima documentation see
http://maxima.sourceforge.net/docs.shtml/.

AUTHORS:

- William Stein (2005-12): Initial version

- David Joyner: Improved documentation

- William Stein (2006-01-08): Fixed bug in parsing

- William Stein (2006-02-22): comparisons (following suggestion of
  David Joyner)

- William Stein (2006-02-24): *greatly* improved robustness by adding
  sequence numbers to IO bracketing in _eval_line

- Robert Bradshaw, Nils Bruin, Jean-Pierre Flori (2010,2011): Binary library
  interface

This is the interface used by the maxima object::

    sage: type(maxima)
    <class 'sage.interfaces.maxima.Maxima'>

If the string "error" (case insensitive) occurs in the output of
anything from Maxima, a RuntimeError exception is raised.

EXAMPLES: We evaluate a very simple expression in Maxima.

::

    sage: maxima('3 * 5')
    15

We factor `x^5 - y^5` in Maxima in several different ways.
The first way yields a Maxima object.

::

    sage: F = maxima.factor('x^5 - y^5')
    sage: F
    -(y-x)*(y^4+x*y^3+x^2*y^2+x^3*y+x^4)
    sage: type(F)
    <class 'sage.interfaces.maxima.MaximaElement'>

Note that Maxima objects can also be displayed using "ASCII art";
to see a normal linear representation of any Maxima object x. Just
use the print command: use ``str(x)``.

::

    sage: print F
                               4      3    2  2    3      4
                   - (y - x) (y  + x y  + x  y  + x  y + x )

You can always use ``repr(x)`` to obtain the linear
representation of an object. This can be useful for moving maxima
data to other systems.

::

    sage: repr(F)
    '-(y-x)*(y^4+x*y^3+x^2*y^2+x^3*y+x^4)'
    sage: F.str()
    '-(y-x)*(y^4+x*y^3+x^2*y^2+x^3*y+x^4)'

The ``maxima.eval`` command evaluates an expression in
maxima and returns the result as a *string* not a maxima object.

::

    sage: print maxima.eval('factor(x^5 - y^5)')
    -(y-x)*(y^4+x*y^3+x^2*y^2+x^3*y+x^4)

We can create the polynomial `f` as a Maxima polynomial,
then call the factor method on it. Notice that the notation
``f.factor()`` is consistent with how the rest of Sage
works.

::

    sage: f = maxima('x^5 - y^5')
    sage: f^2
    (x^5-y^5)^2
    sage: f.factor()
    -(y-x)*(y^4+x*y^3+x^2*y^2+x^3*y+x^4)

Control-C interruption works well with the maxima interface,
because of the excellent implementation of maxima. For example, try
the following sum but with a much bigger range, and hit control-C.

::

    sage: maxima('sum(1/x^2, x, 1, 10)')
    1968329/1270080

Tutorial
--------

We follow the tutorial at
http://maxima.sourceforge.net/docs/intromax/.

::

    sage: maxima('1/100 + 1/101')
    201/10100

::

    sage: a = maxima('(1 + sqrt(2))^5'); a
    (sqrt(2)+1)^5
    sage: a.expand()
    29*sqrt(2)+41

::

    sage: a = maxima('(1 + sqrt(2))^5')
    sage: float(a)
    82.01219330881975
    sage: a.numer()
    82.01219330881975

::

    sage: maxima.eval('fpprec : 100')
    '100'
    sage: a.bfloat()
    8.20121933088197564152489730020812442785204843859314941221237124017312418754011041266612384955016056b1

::

    sage: maxima('100!')
    93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000

::

    sage: f = maxima('(x + 3*y + x^2*y)^3')
    sage: f.expand()
    x^6*y^3+9*x^4*y^3+27*x^2*y^3+27*y^3+3*x^5*y^2+18*x^3*y^2+27*x*y^2+3*x^4*y+9*x^2*y+x^3
    sage: f.subst('x=5/z')
    (5/z+25*y/z^2+3*y)^3
    sage: g = f.subst('x=5/z')
    sage: h = g.ratsimp(); h
    (27*y^3*z^6+135*y^2*z^5+(675*y^3+225*y)*z^4+(2250*y^2+125)*z^3+(5625*y^3+1875*y)*z^2+9375*y^2*z+15625*y^3)/z^6
    sage: h.factor()
    (3*y*z^2+5*z+25*y)^3/z^6

::

    sage: eqn = maxima(['a+b*c=1', 'b-a*c=0', 'a+b=5'])
    sage: s = eqn.solve('[a,b,c]'); s
    [[a=(25*sqrt(79)*%i+25)/(6*sqrt(79)*%i-34),b=(5*sqrt(79)*%i+5)/(sqrt(79)*%i+11),c=(sqrt(79)*%i+1)/10],[a=(25*sqrt(79)*%i-25)/(6*sqrt(79)*%i+34),b=(5*sqrt(79)*%i-5)/(sqrt(79)*%i-11),c=-(sqrt(79)*%i-1)/10]]

Here is an example of solving an algebraic equation::

    sage: maxima('x^2+y^2=1').solve('y')
    [y=-sqrt(1-x^2),y=sqrt(1-x^2)]
    sage: maxima('x^2 + y^2 = (x^2 - y^2)/sqrt(x^2 + y^2)').solve('y')
    [y=-sqrt((-y^2-x^2)*sqrt(y^2+x^2)+x^2),y=sqrt((-y^2-x^2)*sqrt(y^2+x^2)+x^2)]

You can even nicely typeset the solution in latex::

    sage: latex(s)
    \left[ \left[ a={{25\,\sqrt{79}\,i+25}\over{6\,\sqrt{79}\,i-34}} ,   b={{5\,\sqrt{79}\,i+5}\over{\sqrt{79}\,i+11}} , c={{\sqrt{79}\,i+1  }\over{10}} \right]  , \left[ a={{25\,\sqrt{79}\,i-25}\over{6\,  \sqrt{79}\,i+34}} , b={{5\,\sqrt{79}\,i-5}\over{\sqrt{79}\,i-11}} ,   c=-{{\sqrt{79}\,i-1}\over{10}} \right]  \right] 

To have the above appear onscreen via ``xdvi``, type
``view(s)``. (TODO: For OS X should create pdf output
and use preview instead?)

::

    sage: e = maxima('sin(u + v) * cos(u)^3'); e
    cos(u)^3*sin(v+u)
    sage: f = e.trigexpand(); f
    cos(u)^3*(cos(u)*sin(v)+sin(u)*cos(v))
    sage: f.trigreduce()
    (sin(v+4*u)+sin(v-2*u))/8+(3*sin(v+2*u)+3*sin(v))/8
    sage: w = maxima('3 + k*%i')
    sage: f = w^2 + maxima('%e')^w
    sage: f.realpart()
    %e^3*cos(k)-k^2+9

::

    sage: f = maxima('x^3 * %e^(k*x) * sin(w*x)'); f
    x^3*%e^(k*x)*sin(w*x)
    sage: f.diff('x')
    k*x^3*%e^(k*x)*sin(w*x)+3*x^2*%e^(k*x)*sin(w*x)+w*x^3*%e^(k*x)*cos(w*x)
    sage: f.integrate('x')
    (((k*w^6+3*k^3*w^4+3*k^5*w^2+k^7)*x^3+(3*w^6+3*k^2*w^4-3*k^4*w^2-3*k^6)*x^2+(-18*k*w^4-12*k^3*w^2+6*k^5)*x-6*w^4+36*k^2*w^2-6*k^4)*%e^(k*x)*sin(w*x)+((-w^7-3*k^2*w^5-3*k^4*w^3-k^6*w)*x^3+(6*k*w^5+12*k^3*w^3+6*k^5*w)*x^2+(6*w^5-12*k^2*w^3-18*k^4*w)*x-24*k*w^3+24*k^3*w)*%e^(k*x)*cos(w*x))/(w^8+4*k^2*w^6+6*k^4*w^4+4*k^6*w^2+k^8)

::

    sage: f = maxima('1/x^2')
    sage: f.integrate('x', 1, 'inf')
    1
    sage: g = maxima('f/sinh(k*x)^4')
    sage: g.taylor('x', 0, 3)
    f/(k^4*x^4)-2*f/(3*k^2*x^2)+11*f/45-62*k^2*f*x^2/945

::

    sage: maxima.taylor('asin(x)','x',0, 10)
    x+x^3/6+3*x^5/40+5*x^7/112+35*x^9/1152

Examples involving matrices
---------------------------

We illustrate computing with the matrix whose `i,j` entry
is `i/j`, for `i,j=1,\ldots,4`.

::

    sage: f = maxima.eval('f[i,j] := i/j')
    sage: A = maxima('genmatrix(f,4,4)'); A
    matrix([1,1/2,1/3,1/4],[2,1,2/3,1/2],[3,3/2,1,3/4],[4,2,4/3,1])
    sage: A.determinant()
    0
    sage: A.echelon()
    matrix([1,1/2,1/3,1/4],[0,0,0,0],[0,0,0,0],[0,0,0,0])
    sage: A.eigenvalues()
    [[0,4],[3,1]]
    sage: A.eigenvectors()
    [[[0,4],[3,1]],[[[1,0,0,-4],[0,1,0,-2],[0,0,1,-4/3]],[[1,2,3,4]]]]

We can also compute the echelon form in Sage::

    sage: B = matrix(QQ, A)
    sage: B.echelon_form()
    [  1 1/2 1/3 1/4]
    [  0   0   0   0]
    [  0   0   0   0]
    [  0   0   0   0]
    sage: B.charpoly('x').factor()
    (x - 4) * x^3

Laplace Transforms
------------------

We illustrate Laplace transforms::

    sage: _ = maxima.eval("f(t) := t*sin(t)")
    sage: maxima("laplace(f(t),t,s)")
    2*s/(s^2+1)^2

::

    sage: maxima("laplace(delta(t-3),t,s)") #Dirac delta function
    %e^-(3*s)

::

    sage: _ = maxima.eval("f(t) := exp(t)*sin(t)")
    sage: maxima("laplace(f(t),t,s)")
    1/(s^2-2*s+2)

::

    sage: _ = maxima.eval("f(t) := t^5*exp(t)*sin(t)")
    sage: maxima("laplace(f(t),t,s)")
    360*(2*s-2)/(s^2-2*s+2)^4-480*(2*s-2)^3/(s^2-2*s+2)^5+120*(2*s-2)^5/(s^2-2*s+2)^6
    sage: print maxima("laplace(f(t),t,s)")
                                             3                 5
               360 (2 s - 2)    480 (2 s - 2)     120 (2 s - 2)
              --------------- - --------------- + ---------------
                2           4     2           5     2           6
              (s  - 2 s + 2)    (s  - 2 s + 2)    (s  - 2 s + 2)

::

    sage: maxima("laplace(diff(x(t),t),t,s)")
    s*'laplace(x(t),t,s)-x(0)

::

    sage: maxima("laplace(diff(x(t),t,2),t,s)")
    -?%at('diff(x(t),t,1),t=0)+s^2*'laplace(x(t),t,s)-x(0)*s

It is difficult to read some of these without the 2d
representation::

    sage: print maxima("laplace(diff(x(t),t,2),t,s)")
                         !
                d        !         2
              - -- (x(t))!      + s  laplace(x(t), t, s) - x(0) s
                dt       !
                         !t = 0

Even better, use
``view(maxima("laplace(diff(x(t),t,2),t,s)"))`` to see
a typeset version.

Continued Fractions
-------------------

A continued fraction `a + 1/(b + 1/(c + \cdots))` is
represented in maxima by the list `[a, b, c, \ldots]`.

::

    sage: maxima("cf((1 + sqrt(5))/2)")
    [1,1,1,1,2]
    sage: maxima("cf ((1 + sqrt(341))/2)")
    [9,1,2,1,2,1,17,1,2,1,2,1,17,1,2,1,2,1,17,2]

Special examples
----------------

In this section we illustrate calculations that would be awkward to
do (as far as I know) in non-symbolic computer algebra systems like
MAGMA or GAP.

We compute the gcd of `2x^{n+4} - x^{n+2}` and
`4x^{n+1} + 3x^n` for arbitrary `n`.

::

    sage: f = maxima('2*x^(n+4) - x^(n+2)')
    sage: g = maxima('4*x^(n+1) + 3*x^n')
    sage: f.gcd(g)
    x^n

You can plot 3d graphs (via gnuplot)::

    sage: maxima('plot3d(x^2-y^2, [x,-2,2], [y,-2,2], [grid,12,12])')  # not tested
    [displays a 3 dimensional graph]

You can formally evaluate sums (note the ``nusum``
command)::

    sage: S = maxima('nusum(exp(1+2*i/n),i,1,n)')
    sage: print S
                            2/n + 3                   2/n + 1
                          %e                        %e
                   ----------------------- - -----------------------
                      1/n         1/n           1/n         1/n
                   (%e    - 1) (%e    + 1)   (%e    - 1) (%e    + 1)

We formally compute the limit as `n\to\infty` of
`2S/n` as follows::

    sage: T = S*maxima('2/n')
    sage: T.tlimit('n','inf')
    %e^3-%e

Miscellaneous
-------------

Obtaining digits of `\pi`::

    sage: maxima.eval('fpprec : 100')
    '100'
    sage: maxima(pi).bfloat()
    3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117068b0

Defining functions in maxima::

    sage: maxima.eval('fun[a] := a^2')
    'fun[a]:=a^2'
    sage: maxima('fun[10]')
    100

Interactivity
-------------

Unfortunately maxima doesn't seem to have a non-interactive mode,
which is needed for the Sage interface. If any Sage call leads to
maxima interactively answering questions, then the questions can't be
answered and the maxima session may hang. See the discussion at
http://www.ma.utexas.edu/pipermail/maxima/2005/011061.html for some
ideas about how to fix this problem. An example that illustrates this
problem is ``maxima.eval('integrate (exp(a*x), x, 0, inf)')``.

Latex Output
------------

To TeX a maxima object do this::

    sage: latex(maxima('sin(u) + sinh(v^2)'))
    \sinh v^2+\sin u

Here's another example::

    sage: g = maxima('exp(3*%i*x)/(6*%i) + exp(%i*x)/(2*%i) + c')
    sage: latex(g)
    -{{i\,e^{3\,i\,x}}\over{6}}-{{i\,e^{i\,x}}\over{2}}+c

Long Input
----------

The MAXIMA interface reads in even very long input (using files) in
a robust manner, as long as you are creating a new object.

.. note::

   Using ``maxima.eval`` for long input is much less robust, and is
   not recommended.

::

    sage: t = '"%s"'%10^10000   # ten thousand character string.
    sage: a = maxima(t)

TESTS: This working tests that a subtle bug has been fixed::

    sage: f = maxima.function('x','gamma(x)')
    sage: g = f(1/7)
    sage: g
    gamma(1/7)
    sage: del f
    sage: maxima(sin(x))
    sin(x)

This tests to make sure we handle the case where Maxima asks if an
expression is positive or zero.

::

    sage: var('Ax,Bx,By')
    (Ax, Bx, By)
    sage: t = -Ax*sin(sqrt(Ax^2)/2)/(sqrt(Ax^2)*sqrt(By^2 + Bx^2))
    sage: t.limit(Ax=0, dir='+')
    0

A long complicated input expression::

    sage: maxima._eval_line('((((((((((0) + ((1) / ((n0) ^ (0)))) + ((1) / ((n1) ^ (1)))) + ((1) / ((n2) ^ (2)))) + ((1) / ((n3) ^ (3)))) + ((1) / ((n4) ^ (4)))) + ((1) / ((n5) ^ (5)))) + ((1) / ((n6) ^ (6)))) + ((1) / ((n7) ^ (7)))) + ((1) / ((n8) ^ (8)))) + ((1) / ((n9) ^ (9)));')
    '1/n9^9+1/n8^8+1/n7^7+1/n6^6+1/n5^5+1/n4^4+1/n3^3+1/n2^2+1/n1+1'
"""

#*****************************************************************************
#       Copyright (C) 2005 William Stein <[email protected]>
#
#  Distributed under the terms of the GNU General Public License (GPL)
#
#    This code is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
#    General Public License for more details.
#
#  The full text of the GPL is available at:
#
#                  http://www.gnu.org/licenses/
#*****************************************************************************

from __future__ import with_statement

import os, re
import pexpect
#cygwin = os.uname()[0][:6]=="CYGWIN"

from random import randrange

from sage.misc.misc import DOT_SAGE, SAGE_ROOT

##import sage.rings.all

from expect import (Expect, ExpectElement, FunctionElement,
                    ExpectFunction, gc_disabled, AsciiArtString)

from maxima_abstract import (MaximaAbstract, MaximaAbstractFunction,
                             MaximaAbstractElement,
                             MaximaAbstractFunctionElement,
                             MaximaAbstractElementFunction)

# Thanks to the MRO for multiple inheritance used by the Sage's Python,
# this should work as expected
class Maxima(MaximaAbstract, Expect):
    """
    Interface to the Maxima interpreter.

    EXAMPLES::

        sage: m = Maxima()
        sage: m == maxima
        False
    """
    def __init__(self, script_subdirectory=None, logfile=None, server=None,
                 init_code = None):
        """
        Create an instance of the Maxima interpreter.

        TESTS::
        
            sage: Maxima == loads(dumps(Maxima))
            True
            sage: maxima == loads(dumps(maxima))
            True

        Unpickling a Maxima Pexpect interface gives the default interface::

            sage: m = Maxima()
            sage: maxima == loads(dumps(m))
            True

        We make sure labels are turned off (see trac 6816)::
        
            sage: 'nolabels : true' in maxima._Expect__init_code
            True
        """
        # TODO: Input and output prompts in maxima can be changed by
        # setting inchar and outchar..
        eval_using_file_cutoff = 256
        self.__eval_using_file_cutoff = eval_using_file_cutoff
        STARTUP = '%s/local/bin/sage-maxima.lisp'%SAGE_ROOT
        
        # We set maxima's configuration directory to $DOT_SAGE/maxima
        # This avoids that sage's maxima inadvertently loads
        # ~/.maxima/maxima-init.mac
        # If you absolutely want maxima instances that are started by
        # this interface to preload commands, put them in
        # $DOT_SAGE/maxima/maxima-init.mac
        # (we use the "--userdir" option in maxima for this)
        SAGE_MAXIMA_DIR = os.path.join(DOT_SAGE,"maxima")
        
        if not os.path.exists(STARTUP):
            raise RuntimeError, 'You must get the file local/bin/sage-maxima.lisp'

        #self.__init_code = init_code
        if init_code is None:
            # display2d -- no ascii art output
            # keepfloat -- don't automatically convert floats to rationals
            init_code = ['display2d : false', 'keepfloat : true']
        
        # Turn off the prompt labels, since computing them *very
        # dramatically* slows down the maxima interpret after a while.
        # See the function makelabel in suprv1.lisp.
        # Many thanks to [email protected] and also
        # Robert Dodier for figuring this out!
        # See trac # 6818.
        init_code.append('nolabels : true')
        
        MaximaAbstract.__init__(self,"maxima")
        Expect.__init__(self,
                        name = 'maxima',
                        prompt = '\(\%i[0-9]+\)',
                        command = 'maxima-noreadline --userdir="%s" -p "%s"'%(SAGE_MAXIMA_DIR,STARTUP), 
                        maxread = 10000,
                        script_subdirectory = script_subdirectory,
                        restart_on_ctrlc = False,
                        verbose_start = False,
                        init_code = init_code,
                        logfile = logfile,
                        eval_using_file_cutoff=eval_using_file_cutoff)
        self._display_prompt = '<sage-display>'  # must match what is in the file local/bin/sage-maxima.lisp!!
        self._output_prompt_re = re.compile('\(\%o[0-9]+\)')
        self._ask = ['zero or nonzero?', 'an integer?', 'positive, negative, or zero?', 
                     'positive or negative?', 'positive or zero?']
        self._prompt_wait = [self._prompt] + [re.compile(x) for x in self._ask] + \
                            ['Break [0-9]+'] #note that you might need to change _expect_expr if you
                                             #change this
        self._error_re = re.compile('(Principal Value|debugmode|incorrect syntax|Maxima encountered a Lisp error)')
        self._display2d = False



    def _start(self):
        """
        Starts the Maxima interpreter.
        
        EXAMPLES::
        
            sage: m = Maxima()
            sage: m.is_running()
            False
            sage: m._start()
            sage: m.is_running()
            True

        Test that we can use more than 256MB RAM (see trac 6722):

            sage: a = maxima(10)^(10^5)
            sage: b = a^600              # long time -- about 10-15 seconds
            
        """
        Expect._start(self)
        self._sendline(r":lisp (defun tex-derivative (x l r) (tex (if $derivabbrev (tex-dabbrev x) (tex-d x '\\partial)) l r lop rop ))")

        # Remove limit on the max heapsize (since otherwise it defaults
        # to 256MB with ECL).
        self._sendline(":lisp (ext:set-limit 'ext:heap-size 0)")
        self._eval_line('0;')

    def __reduce__(self):
        """
        Implementation of __reduce__ for ``Maxima``.

        EXAMPLES::
        
            sage: maxima.__reduce__()
            (<function reduce_load_Maxima at 0x...>, ())
        """
        return reduce_load_Maxima, tuple([]) #(self.__init_code,)

    def _sendline(self, str):
        """
        Send a string followed by a newline character.

        EXAMPLES::

            sage: maxima._sendline('t : 9;')
            sage: maxima.get('t')
            '9'
        """
        self._sendstr(str)
        os.write(self._expect.child_fd, os.linesep)

    def _expect_expr(self, expr=None, timeout=None):
        """
        Wait for a given expression expr (which could be a regular
        expression or list of regular expressions) to appear in the output
        for at most timeout seconds.

        See `sage.interfaces.expect.Expect._expect_expr` for full details
        on its use and functionality.

        TESTS:

        These tests indirectly show that the interface is working
        and catching certain errors::

            sage: maxima('2+2')
            4
            sage: maxima('integrate(1/(x^3*(a+b*x)^(1/3)),x)')
            Traceback (most recent call last):
            ...
            TypeError: Computation failed since Maxima requested additional
            constraints (try the command "maxima.assume('a>0')"
            before integral or limit evaluation, for example):
            Is  a  positive or negative?
            sage: maxima.assume('a>0')
            [a>0]
            sage: maxima('integrate(1/(x^3*(a+b*x)^(1/3)),x)')
            -b^2*log((b*x+a)^(2/3)+a^(1/3)*(b*x+a)^(1/3)+a^(2/3))/(9*a^(7/3))+2*b^2*atan((2*(b*x+a)^(1/3)+a^(1/3))/(sqrt(3)*a^(1/3)))/(3^(3/2)*a^(7/3))+2*b^2*log((b*x+a)^(1/3)-a^(1/3))/(9*a^(7/3))+(4*b^2*(b*x+a)^(5/3)-7*a*b^2*(b*x+a)^(2/3))/(6*a^2*(b*x+a)^2-12*a^3*(b*x+a)+6*a^4)
            sage: maxima('integrate(x^n,x)')
            Traceback (most recent call last):
            ...
            TypeError: Computation failed since Maxima requested additional
            constraints (try the command "maxima.assume('n+1>0')" before
            integral or limit evaluation, for example):
            Is  n+1  zero or nonzero?
            sage: maxima.assume('n+1>0')
            [n>-1]
            sage: maxima('integrate(x^n,x)')
            x^(n+1)/(n+1)
            sage: maxima.forget([fact for fact in maxima.facts()])
            [[a>0,n>-1]]
            sage: maxima.facts()
            []
            sage: var('a')
            a
            sage: maxima('limit(x^a,x,0)')
            Traceback (most recent call last):
            ...
            TypeError: Computation failed since Maxima requested additional
            constraints (try the command "maxima.assume('a>0')" before
            integral or limit evaluation, for example):
            Is  a  positive, negative, or zero?
        """
        if expr is None:
            expr = self._prompt_wait
        if self._expect is None:
            self._start()
        try:
            if timeout:
                i = self._expect.expect(expr,timeout=timeout)
            else:
                i = self._expect.expect(expr)
            if i > 0:
                v = self._expect.before

                #We check to see if there is a "serious" error in Maxima.
                #Note that this depends on the order of self._prompt_wait
                if expr is self._prompt_wait and i > len(self._ask):
                    self.quit()
                    raise ValueError, "%s\nComputation failed due to a bug in Maxima -- NOTE: Maxima had to be restarted."%v

                j = v.find('Is ')
                v = v[j:]
                k = v.find(' ',4)
                msg = """Computation failed since Maxima requested additional constraints (try the command "maxima.assume('""" + v[4:k] +""">0')" before integral or limit evaluation, for example):\n""" + v + self._ask[i-1]
                self._sendline(";")
                self._expect_expr()
                raise ValueError, msg
        except KeyboardInterrupt, msg:
            #print self._expect.before
            i = 0
            while True:
                try:
                    print "Control-C pressed.  Interrupting Maxima. Please wait a few seconds..."
                    self._sendstr('quit;\n'+chr(3))
                    self._sendstr('quit;\n'+chr(3))
                    self.interrupt()
                    self.interrupt()
                except KeyboardInterrupt:
                    i += 1
                    if i > 10:
                        break
                    pass
                else:
                    break
            raise KeyboardInterrupt, msg

    def _eval_line(self, line, allow_use_file=False,
                   wait_for_prompt=True, reformat=True, error_check=True, restart_if_needed=False):
        """
        Return result of line evaluation.

        EXAMPLES:
        
        We check that errors are correctly checked::
        
            sage: maxima._eval_line('1+1;')
            '2'
            sage: maxima._eval_line('sage0: x == x;')
            Traceback (most recent call last):
            ...
            TypeError: Error executing code in Maxima...


        """
        if len(line) == 0:
            return ''
        line = line.rstrip()
        if line[-1] != '$' and line[-1] != ';':
            line += ';'

        self._synchronize()

        if len(line) > self.__eval_using_file_cutoff:
            # This implicitly uses the set method, then displays
            # the result of the thing that was set.
            # This only works when the input line is an expression.
            # But this is our only choice, since
            # batchmode doesn't display expressions to screen.
            a = self(line)
            return repr(a)
        else:
            self._sendline(line)

        line_echo = self._expect.readline()
        if not wait_for_prompt:
            return
        assert line_echo.strip() == line.strip()

        # This broke in maxima-5.22.1 as discussed in
        # http://trac.sagemath.org/sage_trac/ticket/10187
        #self._expect_expr(self._display_prompt)
        #pre_out = self._before()
        #self._expect_expr()
        #out = self._before()
        #
        # if error_check:
        #     self._error_check(line, pre_out)
        #     self._error_check(line, out)
        #
        # if not reformat:
        #     return out
        #
        # r = self._output_prompt_re
        # m = r.search(out)
        # if m is None:
        #     o = out[:-2]
        # else:
        #     o = out[m.end()+1:-2]
        # o = ''.join([x.strip() for x in o.split()])
        # return o
        #
        # i = o.rfind('(%o')
        # return o[:i]

        self._expect_expr(self._display_prompt)
        out = self._before()        # input echo + output prompt + output
        if error_check:
            self._error_check(line, out)

        if not reformat:
            return out

        self._expect_expr()
        assert len(self._before())==0, 'Maxima expect interface is confused!'

        r = self._output_prompt_re
        m = r.search(out)
        if m is None:
            o = out[:-2]
        else:
            o = out[m.end()+1:-2]
        o = ''.join([x.strip() for x in o.split()])
        return o
        
    def _synchronize(self):
        """
        Synchronize pexpect interface.
        
        This put a random integer (plus one!) into the output stream, then
        waits for it, thus resynchronizing the stream. If the random
        integer doesn't appear within 1 second, maxima is sent interrupt
        signals.
        
        This way, even if you somehow left maxima in a busy state
        computing, calling _synchronize gets everything fixed.
        
        EXAMPLES: This makes Maxima start a calculation::
        
            sage: maxima._sendstr('1/1'*500)
        
        When you type this command, this synchronize command is implicitly
        called, and the above running calculation is interrupted::
        
            sage: maxima('2+2')
            4
        """
        marker = '__SAGE_SYNCHRO_MARKER_'
        if self._expect is None: return
        r = randrange(2147483647)
        s = marker + str(r+1)

        # The 0; *is* necessary... it comes up in certain rare cases
        # that are revealed by extensive testing.
        # Don't delete it. -- william stein
        cmd = '''0;sconcat("%s",(%s+1));\n'''%(marker,r)
        self._sendstr(cmd)
        try:
            try:
                self._expect_expr(timeout=0.5)
                if not s in self._before():
                    self._expect_expr(s,timeout=0.5)
                    self._expect_expr(timeout=0.5)
            except pexpect.TIMEOUT:
                # Don't call self._interrupt() here, as that might send multiple
                # interrupts.  On OS X 10.4, maxima takes a long time to
                # process one interrupt (7.5 seconds on an idle system, but up
                # to a minute on a loaded system) and gets confused by multiple
                # interrupts.  Instead, send just one interrupt and wait.
                # See Trac #9361.
                self._sendstr(chr(3))
                self._expect_expr(timeout=120)
        except pexpect.EOF:
            self._crash_msg()
            self.quit()

    def _batch(self, s, batchload=True):
        """
        Call Maxima's batch or batchload command with a file
        containing the given string as argument.

        EXAMPLES::

            sage: maxima._batch('10003;')
            '...batchload...'
            sage: maxima._batch('10003;',batchload=False)
            '...batch...10003...'
        """
        filename = '%s-%s'%(self._local_tmpfile(),randrange(2147483647))
        F = open(filename, 'w')
        F.write(s)
        F.close()
        if self.is_remote():
            self._send_tmpfile_to_server(local_file=filename)
            tmp_to_use = self._remote_tmpfile()
        tmp_to_use = filename
        
        if batchload:
            cmd = 'batchload("%s");'%tmp_to_use
        else:
            cmd = 'batch("%s");'%tmp_to_use

        r = randrange(2147483647)
        s = str(r+1)
        cmd = "%s1+%s;\n"%(cmd,r)

        self._sendline(cmd)
        self._expect_expr(s)
        out = self._before()
        self._error_check(cmd, out)
        os.unlink(filename)
        return out

    def _quit_string(self):
        """
        Return string representation of quit command.
        
        EXAMPLES::
        
            sage: maxima._quit_string()
            'quit();'
        """
        return 'quit();'

    def _crash_msg(self):
        """
        Return string representation of crash message.

        EXAMPLES::
        
            sage: maxima._crash_msg()
            Maxima crashed -- automatically restarting.
        """
        print "Maxima crashed -- automatically restarting."

    def _error_check(self, cmd, out):
        """
        Check string for errors.

        EXAMPLES::
        
            sage: maxima._error_check("1+1;","Principal Value")
            Traceback (most recent call last):
            ...
            TypeError: Error executing code in Maxima
            CODE:
                1+1;
            Maxima ERROR:
                Principal Value
        """
        r = self._error_re
        m = r.search(out)
        if not m is None:
            self._error_msg(cmd, out)

    def _error_msg(self, cmd, out):
        """
        Raise error with formatted description.

        EXAMPLES::

            sage: maxima._error_msg("1+1;","Principal Value")
            Traceback (most recent call last):
            ...
            TypeError: Error executing code in Maxima
            CODE:
                1+1;
            Maxima ERROR:
                Principal Value
        """
        raise TypeError, "Error executing code in Maxima\nCODE:\n\t%s\nMaxima ERROR:\n\t%s"%(cmd, out.replace('-- an error.  To debug this try debugmode(true);',''))

    ###########################################
    # Direct access to underlying lisp interpreter.
    ###########################################
    def lisp(self, cmd):
        """
        Send a lisp command to Maxima.
        
        .. note::

           The output of this command is very raw - not pretty.
        
        EXAMPLES::
        
            sage: maxima.lisp("(+ 2 17)")   # random formatted output
             :lisp (+ 2 17)
            19
            (
        """
        self._eval_line(':lisp %s\n""'%cmd, allow_use_file=False,
               wait_for_prompt=False, reformat=False, error_check=False)
        self._expect_expr('(%i)')
        return self._before()

    #####
    #
    #####

    def set(self, var, value):
        """
        Set the variable var to the given value.
        
        INPUT:
        
        - ``var`` - string
        
        - ``value`` - string
        
        EXAMPLES::
        
            sage: maxima.set('xxxxx', '2')
            sage: maxima.get('xxxxx')
            '2'
        """
        if not isinstance(value, str):
            raise TypeError
        cmd = '%s : %s$'%(var, value.rstrip(';'))
        if len(cmd) > self.__eval_using_file_cutoff:
            self._batch(cmd, batchload=True)
        else:
            self._eval_line(cmd)
            #self._sendline(cmd)
            #self._expect_expr()
            #out = self._before()
            #self._error_check(cmd, out)

    def clear(self, var):
        """
        Clear the variable named var.

        EXAMPLES::

            sage: maxima.set('xxxxx', '2')
            sage: maxima.get('xxxxx')
            '2'
            sage: maxima.clear('xxxxx')
            sage: maxima.get('xxxxx')
            'xxxxx'
        """
        try:
            self._expect.send('kill(%s)$'%var)
        except (TypeError, AttributeError):
             pass

    def get(self, var):
        """
        Get the string value of the variable var.
        
        EXAMPLES::
        
            sage: maxima.set('xxxxx', '2')
            sage: maxima.get('xxxxx')
            '2'
        """
        s = self._eval_line('%s;'%var)
        return s

    def _function_class(self):
        """
        Return the Python class of Maxima functions.

        EXAMPLES::
        
            sage: maxima._function_class()
            <class 'sage.interfaces.maxima.MaximaFunction'>
        """
        return MaximaFunction

    def _object_class(self):
        """
        Return the Python class of Maxima elements.
        
        EXAMPLES::
        
            sage: maxima._object_class()
            <class 'sage.interfaces.maxima.MaximaElement'>
        """
        return MaximaElement

    def _function_element_class(self):
        """
        Return the Python class of Maxima functions of elements.

        EXAMPLES::
        
            sage: maxima._function_element_class()
            <class 'sage.interfaces.maxima.MaximaFunctionElement'>
        """
        return MaximaFunctionElement

    def _object_function_class(self):
        """
        Return the Python class of Maxima user-defined functions.

        EXAMPLES::
        
            sage: maxima._object_function_class()
            <class 'sage.interfaces.maxima.MaximaElementFunction'>
        """
        return MaximaElementFunction

    ## some old helper functions to wrap the calculus use
    ## of the Maxima interface. these routines expect arguments
    ## living in the symbolic ring and return something
    ## that is hopefully coercible into the symbolic ring again.
##
##    def sr_integral(self,*args):
##        return args[0]._maxima_().integrate(*args[1:])
##
##    def sr_sum(self,expression,v,a,b):
##        sum  = "'sum(%s, %s, %s, %s)" % tuple([repr(expr._maxima_()) for expr in (expression, v, a, b)])
##        result = self.simplify_sum(sum)
##        result = result.ratsimp()
##        return expression.parent()(result)
##
##    def sr_limit(self,ex,*args):
##        return ex._maxima_().limit(*args)
##
##    def sr_tlimit(self,ex,*args):
##        return ex._maxima_().tlimit(*args)
##

def is_MaximaElement(x):
    """
    Returns True if x is of type MaximaElement.
    
    EXAMPLES::
    
        sage: from sage.interfaces.maxima import is_MaximaElement
        sage: m = maxima(1)
        sage: is_MaximaElement(m)
        True
        sage: is_MaximaElement(1)
        False
    """
    return isinstance(x, MaximaElement)

# Thanks to the MRO for multiple inheritance used by the Sage's Python,
# this should work as expected
class MaximaElement(MaximaAbstractElement, ExpectElement):
    """
    Element of Maxima through Pexpect interface.

    EXAMPLES:

    Elements of this class should not be created directly.
    The targeted parent should be used instead::

        sage: maxima(3)
        3
        sage: maxima(cos(x)+e^234)
        cos(x)+%e^234
    """

    def __init__(self, parent, value, is_name=False, name=None):
        """
        Create a Maxima element.
        See ``MaximaElement`` for full documentation.

        EXAMPLES::

           sage: maxima(zeta(7))
           zeta(7)

        TESTS::

            sage: from sage.interfaces.maxima import MaximaElement
            sage: loads(dumps(MaximaElement))==MaximaElement
            True
            sage: a = maxima(5)
            sage: type(a)
            <class 'sage.interfaces.maxima.MaximaElement'>
            sage: loads(dumps(a))==a
            True
        """
        ExpectElement.__init__(self, parent, value, is_name=False, name=None)

    def display2d(self, onscreen=True):
        """
        Return the 2d string representation of this Maxima object.

        EXAMPLES::
        
            sage: F = maxima('x^5 - y^5').factor()
            sage: F.display2d()
                                   4      3    2  2    3      4
                       - (y - x) (y  + x y  + x  y  + x  y + x )
        """
        self._check_valid()
        P = self.parent()
        with gc_disabled():
            P._eval_line('display2d : true$')
            s = P._eval_line('disp(%s)$'%self.name(), reformat=False)
            P._eval_line('display2d : false$')
        s = s.strip('\r\n')

        # if ever want to dedent, see
        # http://mail.python.org/pipermail/python-list/2006-December/420033.html
        if onscreen:
            print s
        else:
            return s


# Thanks to the MRO for multiple inheritance used by the Sage's Python,
# this should work as expected
class MaximaFunctionElement(MaximaAbstractFunctionElement, FunctionElement):
    pass
#    def __init__(self, obj, name):
#        MaximaAbstractFunctionElement.__init__(self, obj, name)
#        FunctionElement.__init__(self, obj, name)


# Thanks to the MRO for multiple inheritance used by the Sage's Python,
# this should work as expected
class MaximaFunction(MaximaAbstractFunction, ExpectFunction):
    pass
#    def __init__(self, parent, name):
#        MaximaAbstractFunction.__init__(self, parent, name)
#        ExpectFunction.__init__(self, parent, name)


# Thanks to the MRO for multiple inheritance used by the Sage's Python,
# this should work as expected
class MaximaElementFunction(MaximaElement, MaximaAbstractElementFunction):
    """
    Maxima user-defined functions.

    EXAMPLES:

    Elements of this class should not be created directly.
    The method ``function`` of the targeted parent should be used instead::

        sage: maxima.function('x,y','h(x)*y')
        h(x)*y
    """

    def __init__(self, parent, name, defn, args, latex):
        """
        Create a Maxima function.
        See ``MaximaElementFunction`` for full documentation.

        EXAMPLES::
        
            sage: maxima.function('x,y','cos(x)+y')
            cos(x)+y

        TESTS::

            sage: f = maxima.function('x,y','x+y^9')
            sage: f == loads(dumps(f))
            True

        Unpickling a Maxima Pexpect interface gives the default interface::

            sage: m = Maxima()
            sage: g = m.function('x,y','x+y^9')
            sage: h = loads(dumps(g))
            sage: g.parent() == h.parent()
            False
        """
        MaximaElement.__init__(self, parent, name, is_name=True)
        MaximaAbstractElementFunction.__init__(self, parent,
                                name, defn, args, latex)


# An instance
maxima = Maxima(init_code = ['display2d : false',
                'domain : complex', 'keepfloat : true'],
                script_subdirectory=None)


def reduce_load_Maxima(): #(init_code=None):
    """
    Unpickle a Maxima Pexpect interface.

    EXAMPLES::
    
        sage: from sage.interfaces.maxima import reduce_load_Maxima
        sage: reduce_load_Maxima()
        Maxima
    """
    return maxima #Maxima(init_code=init_code)

# This is defined for compatibility with the old Maxima interface.
def reduce_load_Maxima_function(parent, defn, args, latex):
    """
    Unpickle a Maxima function.

    EXAMPLES::

        sage: from sage.interfaces.maxima import reduce_load_Maxima_function
        sage: f = maxima.function('x,y','sin(x+y)')
        sage: _,args = f.__reduce__()
        sage: g = reduce_load_Maxima_function(*args)
        sage: g == f
        True
    """
    return parent.function(args, defn, defn, latex)

def __doctest_cleanup():
    """
    Kill all Pexpect interfaces.

    EXAMPLES::
    
        sage: from sage.interfaces.maxima import __doctest_cleanup
        sage: maxima(1)
        1
        sage: maxima.is_running()
        True
        sage: __doctest_cleanup()
        sage: maxima.is_running()
        False
    """
    import sage.interfaces.quit
    sage.interfaces.quit.expect_quitall()