While working a problem this morning I came across a possible solution that involved assigning sequential values to an array element, doing something and then incrementing the value and doing it again. I wondered if such a think could be done using a foreach loop without a secondary assignment;

Based on my reading, I don't believe that what I want can be done. The foreach construct requires simple scalar variables. That being said, has anyone done it?

For example, a typical solution might be ... 

my @tstary = (0,0,0,0,0);
print join(":",@tstary),"\n";
foreach my $idx1 (1..3){
  $tstary[1] = $idx1;
  print join(":",@tstary),"\n";
}

__OUTPUT__
0:0:0:0:0
0:1:0:0:0
0:2:0:0:0
0:3:0:0:0

[download]
This got me thinking, could I use the array elt itself. The foreach construct doesn't allow a array directly, so how about a referece/dereference ... something like 

my @ary03 = (0,0,0,0,0);
print join(":",@ary03),"\n";
foreach ${$ary02[3]} (1..3){  
  $tstary[1] = $idx1;
  print join(":",@tstary),"\n";
}

# this doesn't work with an error of 
# Can't use string ("0") as a symbol ref while "strict refs" in use
# other variations didn't work either

# how about
$aryeltref = \$ary03[1];
foreach $aryeltref (1..3){
  print join(":",(@tstary,$aryeltref)),"\n";
} 

__OUTPUT__
0:0:0:0:0:SCALAR(0x2144a28)
0:0:0:0:0:1
0:0:0:0:0:2
0:0:0:0:0:3

# expected but not quite what I had in mind

# trying foreach $$aryeltref (1..3) produced a "Not a GLOB reference a
+t ... " which makes me wonder if some mojo with the symbol table migh
+t make it work?

[download]
Just a couple of thoughts on a rainy Thursday morning

By the way, I know I can use the three arg for construct for this. I'm just trying to push the boundary of the foreach construct a little


PJ
use strict; use warnings; use diagnostics;

In reply to Using non-scalar constructs in foreach loops by periapt

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