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Re: Perl::Critic says don't modify $_ in list functions and other things

by Lady_Aleena (Curate)
on Jul 09, 2020 at 19:08 UTC ( #11119106=note: print w/replies, xml ) Need Help??


in reply to Perl::Critic says don't modify $_ in list functions and other things

I have updated my code to the following based on suggestions in this thread and chatterbox. With so much wondeful help, I didn't know who to reply to.

my @list = map { chomp($_); $_ } <$fh>; my @uc_list = map { chomp $_; [uc $_] } <$lc_fh>; # used only onc +e my @split_list = map { chomp $_; [ split(/\|/, $_) ] } <$piped_fh>; +# used only once

...has become...

my @list = map { chomp; $_ } <$fh>; my @uc_list = map { chomp; [uc $_] } <$lc_fh>; # used only once my @split_list = map { chomp; [ split(/\|/, $_) ] } <$piped_fh>; # u +sed only once

It appears that explicitely using chomp($_) is what was the problem.

The following code is now a lot simpler once I put the regex into the subroutine instead of munging it in the map.

my @array = map { $_ =~ s/^[\*\+-] (.+)/$1/; some_sub($_, $opt); } @another_array;

...has become...

<code> my @array = map { some_sub($_, $opt); } @another_array;

With the use of /r and a chain of regexen, I was able to change the map.

my @ids = map { $_ =~ s/<.+?>//g; $_ =~ s/^(\d+([stnrdh]{2}|))/NUMWORDS($1)/e; $_ =~ s/(.)\.\w{2,5}?$/$1/; $_ =~ s/&amp/and/g; $_ =~ s/&/and/g; $_ =~ s//Ae/g; $_ =~ s//C/g; $_ =~ s//U/g; $_ =~ s/(||)/e/g; $_ =~ s/#/No/g; $_ =~ s/ /_/g; $_ =~ s/[^\w:.\-]//g; $_; } grep {defined($_)} @base;

...has become...

my @ids = map { s/<.+?>//gr =~ s/^(\d+([stnrdh]{2}|))/NUMWORDS($1)/er =~ s/(.)\.\w{2,5}?$/$1/r =~ s/&amp/and/gr =~ s/&/and/gr =~ s//Ae/gr =~ s//C/gr =~ s//U/gr =~ s/(||)/e/gr =~ s/#/No/gr =~ s/ /_/gr =~ s/[^\w:.\-]//gr } grep { defined } @base;

And Fancy::Map got a complete overhaul with help.

sub fancy_map { my ($opt, $list) = @_; map { if (ref($_)) { fancy_map($opt, $_); } else { my $before = $opt->{'before'} ? $opt->{'before'}.' ' : ''; my $after = $opt->{'after'} ? ' '.$opt->{'after'} : ''; $_ = $before.$_.$after; } } @{$list}; }

...has become...

sub fancy_map { my ($opt, $list) = @_; map { ref $_ ? fancy_map ($opt, $_) : do { my $before = $opt->{'before'} ? $opt->{'before'}.' ' : ''; my $after = $opt->{'after'} ? ' '.$opt->{'after'} : ''; $before.$_.$after; } } @{$list}; }

My only unfinished business with Perl::Critic set on gentle is my two eval(EXPR). I haven't figured out a fix for that at the moment. Does eval BLOCK act differently than eval EXPR?

Also, please note my updated signature! 8)

My OS is Debian 10 (Buster); my perl versions are 5.28.1 local and 5.16.3 or 5.30.0 on my web host depending on the shebang.

No matter how hysterical I get, my problems are not time sensitive. So, relax, have a cookie, and a very nice day!
Lady Aleena

Replies are listed 'Best First'.
Re^2: Perl::Critic says don't modify $_ in list functions and other things
by AnomalousMonk (Bishop) on Jul 09, 2020 at 22:59 UTC
    Does eval BLOCK act differently than eval EXPR?

    Indeed it does. eval BLOCK is parsed at compile time; if there are any syntactic errors, compilation fails. eval EXPR is evaluated at run time; if there are any errors, the error message goes into $@ (see perlvar), the eval returns undef, and the Perl program is free to soldier on.


    Give a man a fish:  <%-{-{-{-<

      I made a few changes to the conditionals around the eval code to possibly keep mistakes from happening when it is used, but I still can't figure out how to convert the eval EXPR into an eval BLOCK. Like converting a map or grep EXPR to a BLOCK, it isn't as easy as putting {} around it instead of () and expecting it to work the same.

      if ($raw_value && $raw_value =~ /\d+\*\d+/) { $total_value = eval($raw_value); # performs multiplication ($amount, $base_value) = split(/\*/,$raw_value); } elsif ($raw_value && $raw_value =~ /\d+\/\d+/) { $base_value = eval($raw_value); # performs division ($total_value, $amount) = split(/\//, $raw_value); } else { $amount = $raw_value; $base_value = $assets->{$lookup_asset} ? $assets->{$lookup_asset} +: 0; $total_value = $amount * $base_value; }

      My OS is Debian 10 (Buster); my perl versions are 5.28.1 local and 5.16.3 or 5.30.0 on web host depending on the shebang.

      No matter how hysterical I get, my problems are not time sensitive. So, relax, have a cookie, and a very nice day!
      Lady Aleena

        Are the numerical parts of $raw_value positive integers? If so, it's going to be simpler and (I suspect) more efficient to use capture groups and do the maths by hand. eg:

        #!/usr/bin/env perl use strict; use warnings; my $raw_value = shift @ARGV; my ($total_value, $base_value, $amount); my $assets = {}; my $lookup_asset = 'foo'; if ($raw_value && $raw_value =~ /(\d+)\*(\d+)/) { $total_value = $1 * $2; # performs multiplication ($amount, $base_value) = ($1, $2); } elsif ($raw_value && $raw_value =~ /(\d+)\/(\d+)/) { $base_value = $1 / $2; # performs division ($total_value, $amount) = ($1, $2); } else { $amount = $raw_value; $base_value = $assets->{$lookup_asset} ? $assets->{$lookup_asset} +: 0; $total_value = $amount * $base_value; } print "Amount: $amount\nBase: $base_value\nTotal: $total_value\nRaw: $ +raw_value\n";

        At least, that's how I would go about it.

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