Am 05.11.2011 23:43, schrieb Ricardo Martins de Abreu Silva:
So, how i can isolate a grammar just for mathematical expression in sympy,
and consequently in python (because the grammar of sympy extends the
grammar of python in relation to mathematical expressions).
I guess that would be Python expression syntax, limiting the allowable
functions to those defined in Sympy. At least that's how I understand
your question.
I don't think this is worth it:
1) Sympy expressions can contain arbitrary Python expressions that might
provide integers. You'd have to distinguish parameter positions of Sympy
functions: those that allow just Sympy objects, those that allow Python
numbers (or strings, or just ints), and those that allow a combination.
2) Sympy defines the set of allowable functions as "whatever is defined
in Sympy's modules". Tomorrow's Sympy might contain additional
functions, so a grammar that enumerates all valid functions will become
outdates very quickly.
3) Import statements pull in functions defined in modules, Sympy modules
or otherwise. You'd need a different grammar for each combination of
import statements. This can be addressed using context-sensitive
grammars (van Wijngaarden two-level grammars come to mind), but these
are much harder to use and much less widely known than the usual
context-free grammars.
It might be a better idea to tell us what you need the syntax for. We
might be able to come up with another way to achieve what you're after.
Regards,
Jo
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