in reply to Soft Array Refs

Hello smknjoe,

As stevieb has shown, a hash is a much better option here. But, for the record, you need no strict 'refs' only if you’re not using eval — in which case, you also have to use package global variables (see perlref#Symbolic-references):

use strict;
use warnings;

our (@table_min_1, @table_min_2, @table_max_1, @table_max_2, $array_na
+me);

while (<DATA>)
{
    chomp;

    if (/Array\s+(\w+)\s+(\d+)/)
    {
        $array_name = 'table_' . $1 . '_' . $2;
    }
    else
    {
        no strict 'refs';
        my @fields = split /\s+/;
        push @$array_name, $fields[1];
    }
}

print "\n";
print "$_ " for @table_max_1, @table_max_2, @table_min_1, @table_min_2
+;
print "\n";

__DATA__
...

[download]

On the other hand, if you are using eval, you can use strict without qualification, along with my lexicals:

use strict;
use warnings;

my (@table_min_1, @table_min_2, @table_max_1, @table_max_2, $array_nam
+e);

while (<DATA>)
{
    chomp;

    if (/Array\s+(\w+)\s+(\d+)/)
    {
        $array_name = '@table_' . $1 . '_' . $2;
        #              ^
    }
    else
    {
        my @fields = split /\s+/;
        eval qq(push $array_name, "$fields[1]");
    }
}

print "\n";
print "$_ " for @table_max_1, @table_max_2, @table_min_1, @table_min_2
+;
print "\n";

__DATA__
...

[download]

Note the additional @ in the second example. In both cases, the output is as desired:

15:43 >perl 1283_SoPW.pl

a b c 1 2 3 d e f 4 5 6

15:43 >

[download]

But, again, don’t do that! :-)

Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

Replies are listed 'Best First'.
Re^2: Soft Array Refs
by smknjoe (Beadle) on Jun 24, 2015 at 16:15 UTC

    Ah so,

    I was somewhat close. I'm still fairly clueless on some of the syntactical subtleties in Perl - single quotes around '@table' for example. I love your printing shortcut at the end - I learn something new everyday. I'm looking to write this code CORRECTLY using hashes instead.

    Thx, Joe
[reply]
      ... single quotes around '@table' ...

      If double-quotes has been used, double-quotish interpolation of an array named  @table_ would have been attempted and, with strict fully enabled (as it is in Athanasius's code), would have crashed compilation. Single-quotes do not interpolate. (Update: The  @ sigil could also be escaped in double-quotes.) 

      c:\@Work\Perl\monks>perl -le
"use warnings;
 use strict;
 ;;
 print qq{@table};
"
Possible unintended interpolation of @table in string at -e line 1.
Global symbol "@table" requires explicit package name at -e line 1.
Execution of -e aborted due to compilation errors.

c:\@Work\Perl\monks>perl -le
"use warnings;
 use strict;
 ;;
 my @table = qw(fee fie foe);
 ;;
 print qq{double-quote array interpolation: (@table)};
 ;;
 print q{single-quote, no interpolation: (@table)};
 ;;
 print qq{double-quote, sigil escaped: (\@table)};
"
double-quote array interpolation: (fee fie foe)
single-quote, no interpolation: (@table)
double-quote, sigil escaped: (@table)

      [download]

      Update: Changed code examples to consolidate compiling code examples into single group of statements.

      Give a man a fish:  <%-(-(-(-<

[reply]
[d/l]
[select]

        Correct.

        I noticed this after it failed the first time and I looked closer at Athanasius's code. Gvim's context-sensitive color-coding also clued me in to what was going on.

        As a follow-up, I was very successful in coding this as a nested hash - it took very little time and I was quite pleased at how easy it was. It was far less code than my previous attempt using if-statements and arrays AND no soft references!

[reply]

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