Christian Sturm wrote:
> do you know a short and easy way to iterate a block X times?
Aye ;-)
> I know, one could use while, for, ... but there are some reasons,
> why they don't fit.
>
> All these versions are long. I really like Perl, because you can
> do thing with shorter code. In all these loops you must define a
> variable which gets increased or decreased in each iteration.
No.
for ^5 { say "hi" }
I don't define any variable to be incremented, and it's not really that
many keystrokes.
> Here is the next problem. To be honest I don't know much about
> how to make a program efficient, but for me it seems to be
> inefficient to have a calculation, a comparison each time and two
> variables (or one variable, which changes every time and a
> constant) only for doing something X times. Especially if I know
> how often I want to run the block before I start it and if I
> don't need to know the value of $_ in
>
> for 1..5 {
> $value = $_;
> }
In a perfect world the optimizer finds out by static analysis that $_ is
not needed in the block, and doesn't generate it. In the real world we
don't have any optimizing Perl 6 compilers yet.
> So where is this needed?
>
> I know Perl isn't the best language when I want to do big
> calculations, but the Lucas?Lehmer primality test[1] would be one
> example.
>
> I'm not sure how this should look like. Ruby allows something
> like this. So maybe one should have look there. Here a few
> suggestions:
>
>
> $X.times {
> $s = $s * $s;
> }
It always felt weird to me to delegate control flow to integers - but
maybe that's just me.
> $X * {
> $s = $s * $s
> }
>
> iterate ( $X )
> {
> $s = $s * $s;
> }
>
>
> I guess something always has to be increased/decreased if it
> comes down to C/Assembly, but even if it doesn't make it faster
> it would make to code smaller and easier to understand.
Would it? given that Perl 6 has at least 4 loop constructs today (for,
while, map, loop), and that * is already taken both as an infix operator
and a term, I'm not sure about that one.
Cheers,
Moritz
