Re: Logical/defined or as lvalue

[ikegami]

Is ( X || Y ) = Z; really something we want to see in our code? When would it be useful?

[NERDVANA]

We have ($w? $x : $y)= $z so why not?

[LanX]

Well yes, according to Wikipedia is PHP implementing the "Elvis operator"
• $x ?: $y
as
• $x ? $x : $y

But I think Perl has bigger fish to frie.

[NERDVANA]

My point was that if the ternary conditional is an lvalue, then I don't see why not to make the '||' and '//' operators lvalues. It would result in better consistency.

[jo37]

... implementing the "Elvis operator" ... as $x ? $x : $y

Actually, I read the opposite from the Wiki article:

... the Elvis operator expression A ?: B is approximately equivalent to the ternary conditional expression A ? A : B

... something like ... x = f() ?: g() ... is equivalent to ... the conditional ternary operator x = f() ? f() : g() except that it does not evaluate f() twice if it yields truthy.

Accentuations by me.

[ikegami]

Many reasons why not. I already gave the two primary ones: lack of readability (due to its rare and unexpected use) and lack of usefulness.

If anything, I read your post as an argument against ( W ? X : Y ) = Z. But that has at least some modicum of usefulness.

[jo37]

When would it be useful?

Consider items from @list to be counted, with one "given" set and a "rest". A pre-initialized hash %h1 holds the "given" set and an empty hash %h2 counts the rest. Then we could:

${\($h1{$_} // ($h2{$_} //= 0))}++ for @list;

[ikegami]

If you're going to count them all, I don't see the point of having the counts split across two hashes. If there's an important distinction between the two sets of strings, you would need those lists, and you could access the counts of either lists.

[LanX]

If I wanted to do this, I'd count only in one hash and use a hash-slice to extract the "given" ones.

Less code and more flexible.

Update

Alternatively a HoH where the first key decides what is given or rest.