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Postings from July 2010
On Thu, Jul 15, 2010 at 9:33 AM, demerphq <demerphq@gmail.com> wrote:
>> On the other hand, it may not be documented or specified, but I think most
>> people would expect that in the following, f() is called before g():
>> $f() . $g()
>
> Hmm. I don't know that I would. If we want this to be the case then
> IMO we should document it.
I thought this was actually specified in terms of precedence and
associativity, but if I read it narrowly as written, it's not. At
best it's implied.
But maybe we can get there by analogy with some identity operations.
Consider this:
q{} . $f() . $g()
Concatenation is left associative so C<< q{} . $f() >> is evaluated
first. A function call has higher precedence so $f() is evaluated
before the concatenation. Only then is $g() evaluated.
Or consider this:
$f() ** $g() ** 1
Exponentiation is right associative so C<< $g() ** 1 >> is evaluated
first. Function call has higher precedence so $g() is evaluated
before exponentiation. Only then is $f() evaluated.
The implication is that in any binary operation, the terms are
evaluated in order of the associativity of the operation.
I don't know if that's guaranteed to be true in the interpreter. If
it *is*, then we should add a note to that effect in the perlop
paragraph on operator associativity. If *not*, then I wonder why not
and what it would take to make it true.
The other thing I wonder is whether clarifying precedence of variable
terms (including resolution of ties or magic) versus other terms would
help resolve the ambiguities in any way, but I haven't really followed
that thought through.
-- David
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