Re^2: finding number of contiguous letters

[otto]

Far better solutions have been presented, but here is another. I was considering how to do if we had tail recursion. I had been hoping to place all code in the argument list...

sub parts {
    my ( $cnt, $ra_out, $ra_val, $ra_in ) = @_;
    if( $#$ra_val != $cnt ){ #working array not full
        if( $#$ra_in > -1 ){ #fill it up
            push(@$ra_val, shift(@$ra_in));
            parts( $cnt, $ra_out, $ra_val, $ra_in );
        } else {             #done with list
            return;
        }
   } else {
        push(@$ra_out, join('',@$ra_val));                #add to outp
+ut array, joined ltr string
        shift(@$ra_val);                                  #rip off fir
+st ltr
        push(@$ra_val, shift(@$ra_in)) if($#$ra_in > -1); #add new ltr
+, if any remaining
        parts( $cnt, $ra_out, $ra_val, $ra_in );
    }
}
my @in  = split( '', "computer" ); # input array of individual letters
my @out;                           # out array of strings each of $cnt
++1 ltrs
my @val;                           # working array of individual lette
+rs, $cnt+1 elements
parts( 2, \@out, \@val, \@in );
#results in @out

..Otto

[blazar]

I was considering how to do if we had tail recursion.

We do have tail recursion. Well not really: sort of. That's courtesy of magic goto: but then of course one has to explicitly make use of it, not that TR is automatically recognized, which is what you clearly meant.

[otto]

Blazar,

You got me thinking, I'm going to play with this some more, but first... are sub arguments, ie a list, evaluated in order?

For example suppose a list is composed of ( <a>, <b>, <c> )where each of the a, b, c are one or more sub calls that may mutate some value, which may be used by others further down the list, will the list values be evaluated in order of a, b, c, or is it undefined?

I quickly looked at the sub function and the comma operator which did not shed any light, or at least I didn't see it...

.. Otto

[blazar]

For example suppose a list is composed of ( <a>, <b>, <c> ) where each of the a, b, c are one or more sub calls that may mutate some value, which may be used by others further down the list, will the list values be evaluated in order of a, b, c, or is it undefined?

IIUC, why don't you find out yourself?

#!/usr/bin/perl -l

use strict;
use warnings;

BEGIN {
    my $foo;
    sub foo () { $foo }
    for my $n (qw/a b c d e f/) {
        no strict 'refs';
        *$n = sub () { warn $n; $foo++ };
    }
}

my $arr=(a,b,c,d,e,f);
print foo, $arr;
    
__END__