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Postings from November 2003
Luke Palmer started a discussion:
> I see this idiom a lot in code. You loop through some values on a
> condition, and do something only if the condition was never true.
> $is_ok is a control flow variable, something I like to minimize. Now,
> there are other ways to do this:
>
> if (0..6 ==> grep -> $t { abs(@new[$t] - @new[$t+1]) })
> { ... }
>
> But one would say that's not the cleanest thing in the world.
Only because you overdid the sugar. :
if grep {abs(@new[$^t] - @new[$^t+1]) > 3} 0..6
{ ... }
is pretty clean.
But, in any case, handling exceptional cases are what exceptions are for:
try {
for 0..6 -> $t {
die if abs(@new[$t] - @new[$t+1]) > 3;
}
CATCH {
push @moves: [$i, $j];
}
}
As regards return values of control structures, I had always assumed that:
* scalar control structures like C<if>, C<unless>, and C<given> return
the value of the last statement in their block that they evaluated;
* vector control structures like C<loop>, C<while>, and C<for> in a list
context return a list of the values of the last statement each
iteration evaluated;
* vector control structures like C<loop>, C<while>, and C<for> in a scalar
context return an integer indicating the number of times their block
was iterated.
So we might also write:
for 0..6 -> $t {
last if abs(@new[$t] - @new[$t+1]) > 3;
}
< 7 and push @moves: [$i, $j];
Damian
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