sympy.py

   1 import sympy_py
   2 _mode = 'py'
   3
   4 import os
   5 if os.getenv('SYMPY_PY', '').lower() in ['y', 'yes']:
   6     print 'I: forced to be pure python'
   7
   8 else:
   9     try:
  10         # XXX better not * ?
  11         print 'I: import sympy_pyx ...',
  12         from sympy_pyx import *
  13
  14         # XXX figure out how to put this into sympy_pyx.pyx:
  15         BASIC   = 0
  16         SYMBOL  = 1
  17         ADD     = 2
  18         MUL     = 3
  19         POW     = 4
  20         INTEGER = 5
  21
  22         from sympy_pyx import _Basic
  23
  24         # Cython/Pyrex do not support __new__, so we have to define Basic here
  25         class Basic(_Basic):
  26
  27             def __new__(cls, args):
  28                 o = _Basic.__new__(cls)
  29                 o._set_rawargs(tuple(args))
  30                 return o
  31
  32
  33     except ImportError, e:
  34         print 'fail  (%s)' % e
  35         print 'W: can\'t import sympy_pyx -- will be pure python'
  36
  37     else:
  38         print 'ok'
  39         _mode = 'pyx'
  40
  41
  42 if _mode == 'pyx':
  43     from sympy_pyx import *
  44 else:
  45     from sympy_py import *
  46
  47 def var(s):
  48     """
  49         Create a symbolic variable with the name *s*.
  50
  51         INPUT:
  52             s -- a string, either a single variable name, or
  53                  a space separated list of variable names, or
  54                  a list of variable names.
  55
  56         NOTE: The new variable is both returned and automatically injected into
  57         the parent's *global* namespace.  It's recommended not to use "var" in
  58         library code, it is better to use symbols() instead.
  59
  60         EXAMPLES:
  61         We define some symbolic variables:
  62             >>> var('m')
  63             m
  64             >>> var('n xx yy zz')
  65             (n, xx, yy, zz)
  66             >>> n
  67             n
  68
  69     """
  70     import re
  71     import inspect
  72     frame = inspect.currentframe().f_back
  73
  74     try:
  75         if not isinstance(s, list):
  76             s = re.split('\s|,', s)
  77
  78         res = []
  79
  80         for t in s:
  81             # skip empty strings
  82             if not t:
  83                 continue
  84             sym = Symbol(t)
  85             frame.f_globals[t] = sym
  86             res.append(sym)
  87
  88         res = tuple(res)
  89         if len(res) == 0:   # var('')
  90             res = None
  91         elif len(res) == 1: # var('x')
  92             res = res[0]
  93                             # otherwise var('a b ...')
  94         return res
  95
  96     finally:
  97         # we should explicitly break cyclic dependencies as stated in inspect
  98         # doc
  99         del frame
 100
 101
 102
 103 # for debugging
 104 x = Symbol('x')
 105 y = Symbol('y')
 106 z = Symbol('z')
 107 i = Integer(2)
 108
 109 x2= Symbol('x')
 110
 111
 112 e = (x+y)**2
 113
 114
 115 class sin(Basic):
 116
 117     def __new__(cls, arg):
 118         if arg == 0:
 119             return Integer(0)
 120         else:
 121             obj = Basic.__new__(cls, (arg,))
 122             return obj
 123
 124     def __repr__(self):
 125         return "sin(%s)" % self.args[0]
 126