[Python-Dev] pyc files, constant folding and borderline portability issues
p.f.moore at gmail.com
Tue Apr 7 12:33:39 CEST 2009
2009/4/7 Cesare Di Mauro <cesare.dimauro at a-tono.com>:
> The principle that I followed on doing constant folding was: "do what Python
> will do without constant folding enabled".
> So if Python will generate
> LOAD_CONST 1
> LOAD_CONST 2
> the constant folding code will simply replace them with a single
> LOAD_CONST 3
> When working with such kind of optimizations, the temptation is to
> apply them at any situation possible. For example, in other languages
> a = b * 2 * 3
> will be replaced by
> a = b * 6
> In Python I can't do that, because b can be an object which overloaded
> the * operator, so it *must* be called two times, one for 2 and one for 3.
> That's the way I choose to implement constant folding.
That sounds sufficiently "super risk-averse" to me, so I'm in favour
of constant folding being implemented with this attitude :-)
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