Re: join string in 2D array

Consider the code below....

use warnings;
use strict;
use Data::Dumper qw(Dumper);

my @clk =  ('ux_prim_clk', 'ux_side_clk', 'ux_xtal_frm_refclk');

#my @clk_output = map [ split /_/, $_ ], @clk;

# Just as a note: Performance is the same with explict loop.
# Every map statement can be expressed as a foreach() loop.
# This is the same your previous statement - nothing wrong with it
# just demo'ing what the map actually does...

my @clk_output; 
foreach my $clk_line (@clk)
{
   push @clk_output, [split "_",$clk_line];
}

print Dumper \@clk_output;

my @clk_new;
foreach my $row_ref (@clk_output)
{
    push @clk_new, join ("_",@$row_ref);
}

print Dumper \@clk_new;

__END__
$VAR1 = [
          [
            'ux',
            'prim',
            'clk'
          ],
          [
            'ux',
            'side',
            'clk'
          ],
          [
            'ux',
            'xtal',
            'frm',
            'refclk'
          ]
        ];
$VAR1 = 'ux_prim_clk';
$VAR2 = 'ux_side_clk';
$VAR3 = 'ux_xtal_frm_refclk';
[download]

Could also be coded...this does the same thing:

use warnings;
use strict;
use Data::Dumper qw(Dumper);

my @clk =  ('ux_prim_clk', 'ux_side_clk', 'ux_xtal_frm_refclk');

my @clk_output = map [ split /_/, $_ ], @clk;

print Dumper \@clk_output;

my @clk_new = map{my $line =join ("_", @$_); $line}@clk_output;

print Dumper \@clk_new;
[download]

Comment on Re: join string in 2D array Select or Download Code

Replies are listed 'Best First'.
Re^2: join string in 2D array by AnomalousMonk (Archbishop) on May 05, 2019 at 00:51 UTC
Could also be coded...this does the same thing: `...` `my @clk_new = map{my $line =join ("_", @$_); $line}@clk_output;` But isn't it also true that the statement `my @clk_new = map{my $line =join ("_", @$_)}@clk_output;` would do the same thing? In which case, there seems to be no point to assigning to a lexical within the map block, so we're back to `my @clk_new = map{ join('_', @$_) }@clk_output;` or `my @clk_new = map join('_', @$_), @clk_output;` Prior to the introduction of the `/r` modifier for `s///` substitution in Perl version 5.14 (see Regexp Quote Like Operators in perlop), there was sometimes a need for a `map` statement like `map { (my $r = $_) =~ s{ ... }{foo}xms; $r; }` to avoid changing the aliased referent of `$_` in a data flow, but it doesn't seem useful here. (I can't tell you how many times I've had to remember to do this when a bunch of unexpected `'1'` characters suddenly showed up in my output!) A similar situation might arise if one wanted to stick a debug print-point `map { print "... $_ ..."; $_; }` into the middle of a data flow. Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re^3: join string in 2D array by Marshall (Canon) on May 05, 2019 at 03:48 UTC
All completely valid points. However, assigning to a simple lexical scalar within a map block is dirt cheap both in terms of memory and execution speed. Perl is probably gonna do something like that internally anyway, it just won't have a "name". If assigning a lexical name makes the code more clear, then why not? In this thread, I think the OP has some confusion about maps and foreach loops. So I showed a couple of ways for each significant loop in the code.	[reply]


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