doc/linexpr.rst

   1 Linear Expression Module
   2 ========================
   3
   4 This class implements linear expressions. A linear expression is….
   5
   6 .. py:class:: Expression
   7
   8     .. py:method:: __new__(cls, coefficients=None, constant=0)
   9
  10         Create and return a new linear expression from a string or a list of coefficients and a constant.
  11
  12     .. py:method:: coefficient(self, symbol)
  13
  14         Return the coefficient value of the given symbol.
  15
  16     .. py:method:: coefficients(self)
  17
  18         Return a list of the coefficients of an expression
  19
  20     .. attribute:: constant
  21
  22         Return the constant value of an expression.
  23
  24     .. attribute:: symbols
  25
  26         Return a list of symbols in an expression.
  27
  28     .. attribute:: dimension
  29
  30         Return the number of variables in an expression.
  31
  32     .. py:method:: isconstant(self)
  33
  34         Return ``True`` if an expression is a constant.
  35
  36     .. py:method:: issymbol(self)
  37
  38         Return ``True`` if an expression is a symbol.
  39
  40
  41     .. py:method:: values(self)
  42
  43         Return the coefficient and constant values of an expression.
  44
  45     .. py:method:: __add__(self, other)
  46
  47         Return the sum of *self* and *other*.
  48
  49     .. py:method:: __sub__(self, other)
  50
  51         Return the difference between *self* and *other*.
  52
  53     .. py:method:: __mul__(self, other)
  54
  55         Return the product of *self* and *other* if *other* is a rational number.
  56
  57     .. py:method:: __eq__(self, other)
  58
  59         Test whether two expressions are equal.
  60
  61     .. py:method:: __le__(self, other)
  62                    self <= other
  63
  64         Create a new polyhedra from an expression with a single constraint as *self* less than or equal to *other*.
  65
  66     .. py:method:: __lt__(self, other)
  67                    self < other
  68
  69        Create a new polyhedra from an expression with a single constraint as *self* less than *other*.
  70
  71     .. py:method:: __ge__(self, other)
  72                    self >= other
  73
  74         Create a new polyhedra from an expression with a single constraint as *self* greater than or equal to *other*.
  75
  76     .. py:method:: __gt__(self, other)
  77                    self > other
  78
  79         Create a new polyhedra from an expression with a single constraint as *self* greater than *other*.
  80
  81     .. py:method:: scaleint(self)
  82
  83         Multiply an expression by a scalar to make all coefficients integer values.
  84
  85     .. py:method:: subs(self, symbol, expression=None)
  86
  87         Subsitute the given value into an expression and return the resulting expression.
  88
  89
  90     .. py:method:: fromstring(self)
  91
  92         Create an expression from a string.
  93
  94     .. py:method:: fromsympy(self)
  95
  96         Convert sympy object to an expression.
  97
  98     .. py:method:: tosympy(self)
  99
 100         Return an expression as a sympy object.
 101
 102 .. py:class:: Symbol(Expression)
 103
 104     .. py:method:: __new__(cls, name)
 105
 106         Create and return a symbol from a string.
 107
 108     .. py:method::  symbols(names)
 109
 110         This function returns a sequence of symbols with names taken from names argument, which can be a comma or whitespace delimited string, or a sequence of strings.
 111
 112     .. py:method:: asdummy(self)
 113
 114         Return a symbol as a :class:`Dummy` Symbol.
 115
 116 .. py:class:: Dummy(Symbol)
 117
 118     This class returns a dummy symbol to ensure that no variables are repeated in an expression. This is useful when the user needs to have a unique symbol, for example as a temporary one in some calculation, which is going to be substituted for something else at the end anyway.
 119
 120     .. py:method:: __new__(cls, name=None)
 121
 122         Create and return a new dummy symbol.
 123
 124
 125 .. py:class:: Rational(Expression, Fraction)
 126
 127     This class represents integers and rational numbers of any size.
 128
 129     .. attribute:: constant
 130
 131         Return rational as a constant.
 132
 133     .. py:method:: isconstant(self)
 134
 135         Test whether a value is a constant.
 136
 137     .. py:method:: fromsympy(cls, expr)
 138
 139        Create a rational object from a sympy expression
 140