Re: Making control variables local in a loop statement

[Matthew Walton]

Austin Hastings wrote:
David Storrs wrote:
On Thu, Jan 13, 2005 at 07:35:19PM -0500, Joe Gottman wrote:
 

  In Perl5,  given code like
   for (my $n = 0; $n < 10; ++$n) {.}
the control variable $n will be local to the for loop.  In the 
equivalent
Perl6 code
  loop my $n = 0; $n < 10; ++$n {.}

$n will not be local to the loop but will instead persist until the 
end of
enclosing block.    

Actually, I consider this a good thing.  There are lots of times when
I would LIKE my loop variable to persist and, in order to get that, I
need to do the following:
    my $n;
    for ($n=0; $n<10; ++$n) {...}
    ...do stuff with $n...
It's a minor ugliness, but it itches at me.  Under the new Perl6
rules, I can easily have it either way. 
      {for (my $n=0; $n<10; ++$n) {...}}   # Local to loop
       for (my $n=0; $n<10; ++$n) {...}    # Persistent

--Dks
 

But there's no clean way to make some of them temporary and some 
persistent.

This seems like a legitimate place for "saying what you intend", viz:
for (my $n is longlasting = 0, $m = 1; ...) {...}
Albeit that's a lame example of how to do it.
What's not clean about
{
  loop my $n = 0; $n < 10; $n++ {
    ...
  }
}
? Works fine for me, shows the scope boundaries very clearly indeed, 
just the kind of thing a lot of languages are missing, IMO.

Of course, this example's really bad because it's much better written
for 0..9 {
  ...
}
In which case I assume that it only clobbers the topic inside the block, 
not outside it, as it's somewhat like

for 0..9 -> $_ {
  ...
}
To write it explicitly. Or am I barking up the wrong tree completely?