Colin J. Williams
cjw at sympatico.ca
Fri Sep 23 14:43:59 CEST 2005
Jeremy Sanders wrote:
> Peter Hansen wrote:
>>Almost anything is possible in Python, though whether the underlying
>>design idea is sound is a completely different question. (Translation:
>>try the following pseudo-code, but I have my suspicions about whether
>>what you're doing is a good idea. :-) )
> What I'd like to do precisely is to be able to evaluate an expression like
> "a+2*b" (using eval) where a and b are objects which behave like numarray
> arrays, but whose values aren't computed until their used.
Could you not have functions a and b each of which returns a NumArray
Your expression would then be something like a(..)+2*b(..).
> I need to compute the values when used because the arrays could depend on
> each other, and the easiest way to get the evaluation order correct is to
> only evaluate them when they're used.
> An alternative way is to do some string processing to replace a with
> computearray("a") in the expression or something horrible like that.
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