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class Symbol(object): 
class Symbol(object): 
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""" 
""" 
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`Symbol` objects are placeholders for a single mathematic symbol, such as 
`Symbol` objects are placeholders for a single mathematical symbol, such as 
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'x', or for arbitrarily complex mathematic expressions such as 
'x', or for arbitrarily complex mathematical expressions such as 
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'c*x**4+alpha*exp(x)2*sin(beta*x)', where 'alpha', 'beta', 'c', and 'x' 
'c*x**4+alpha*exp(x)2*sin(beta*x)', where 'alpha', 'beta', 'c', and 'x' 
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are also `Symbol`s (the symbolic 'atoms' of the expression). 
are also `Symbol`s (the symbolic 'atoms' of the expression). 
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be resolved by substituting numeric values and/or escript `Data` objects 
be resolved by substituting numeric values and/or escript `Data` objects 
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for the atoms. To facilitate the use of `Data` objects a `Symbol` has a 
for the atoms. To facilitate the use of `Data` objects a `Symbol` has a 
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shape (and thus a rank) as well as a dimension (see constructor). 
shape (and thus a rank) as well as a dimension (see constructor). 
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`Symbol`s are useful to perform mathematic simplifications, compute 
`Symbol`s are useful to perform mathematical simplifications, compute 
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derivatives and as coefficients for nonlinear PDEs which can be solved by 
derivatives and as coefficients for nonlinear PDEs which can be solved by 
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the `NonlinearPDE` class. 
the `NonlinearPDE` class. 
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""" 
""" 