On Sun, 2007-09-16 at 20:02 +0100, Nuno Lopes wrote:
> >My proposal is the following:
> >some functions when fed with constant arguments always return a
> >constant
> >value, too. e.g.:
> >strlen('abcd') === 4.
>
> I like the general idea.
>
> Would there be some caveats with stuff like this if it is possible to
> change the charset at runtime?
>
> I guess it is important to be aware of whether a function is affected
> by different settings (and if these settings can be changed at
> runtime) to conclude if a function really is deterministic at this
> level.
uhm, damn, right. strlen() wasn't a good example.. my bad, sorry :S
Anyway, you got the idea :)
Nothing wrong with strlen as far as I can tell:
- In PHP 5 we only have binary strings so strlen() works independent
from any charsets and encodings by just counting bytes.
- In PHP 6 we know - assuming the parameter is a constant string - the
encoding at compile time, therefore it could be used.
The only edge-case I see is if somebody uses mbstring.func_overload and
overwrites strlen()
exactly. I was thinking in mbstring, too. As long as there is some run-time
setting that can affect a function, we cannot replace its call blindly with
its value. Then only a more intelligent optimizer can do inference on the
code and figure out if it's safe or not to replace the function call.
My proposal was to mark functions susceptible of that "blind" replacement
only.
Nuno
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