Linear Expression Module
========================

This class implements linear expressions. A linear expression is….

.. py:class:: Expression


    .. py:method:: coefficient(self, symbol)
        
        Return the coefficient value of the given symbol.
        
    .. py:method:: coefficients(self)
        
        Return a list of the coefficients of an expression
        
    .. attribute:: constant
    
        Return the constant value of an expression.
        
    .. attribute:: symbols
    
        Return a list of symbols in an expression.                            
    
    .. attribute:: dimension
    
        Return the number of variables in an expression.
        
    .. py:method:: __sub__(self, other)
    
        Return the difference between *self* and *other*.
               
    .. py:method:: subs(self, symbol, expression=None)
    
        Subsitute the given value into an expression and return the resulting expression.

    .. py:method:: fromsympy(self)
    
        Convert sympy object to an expression.
        
    .. py:method:: tosympy(self)
    
        Return an expression as a sympy object.    

.. py:class:: Symbol(Expression)
        
          
.. py:class:: Dummy(Symbol)

This class returns a dummy symbol to ensure that each no variables are repeated in an expression