4 ms·

To be clear here, that Perl 5 code is not production grade code and i'd send anyone trying to commit that to a repo back to the hash mines.

bglazer 12y ago
Could you elaborate a little? I ask because the Perl 5 code looks a lot like the Perl that I write. I'd like to improve, but the existing Perl code that I'm writing on top of is really bad. Like really, really bad. I don't have much quality Perl to compare against.
- Mithaldu 12y ago
  Two examples: $freq{substr $grade{$_}, 0, 1}++ for keys %grade; better: $freq{$_}++ for map { substr $_, 0, 1 } values %grade; best: my @letters = map { substr $_, 0, 1 } values %grade; $freq{$_}++ for @letters; ---------------------------- and open my $fh, '<:utf8', "grades.txt" or die "Failed to open file: $!"; my %grade; while (<$fh>) { m/^(\w+) \s+ ([A-F][+-]?)$/x or die "Can't parse line '$_'"; $grade{$1} = $2; }; better: use 5.010; use IO::All -binary, -utf8; my $line_format = qr/ ^ # line start (?<student>\w+) # name \s+ # gap (?<grade>[A-F][+-]?) # grade $ # line end /x; my $fh = io->file("grades.txt"); my %grade; while (my $line = $io->getline) { die "Can't parse line '$line'" if $line !~ $line_format; $grade{$+{student}} = $+{grade}; }
  - hvs 12y ago
    Very nicely done. I use Perl in my everyday job, and its nice to see that some people still know how to write good Perl.
  - Ultimatt 12y ago
    5.10 in production? Surely you're joking! 5.8 or bust.
  - pjfl 12y ago
    You should have use strict; use warnings; then you would have noticed the my $fh and the $io->getline error
    - Mithaldu 12y ago
      Dammit, you're right. I was working in a buffer without perl instrumentation enabled because i was composing a comment, not a script. Now i can't edit the comment anymore. :/
peteretep 12y ago
Exactly. Perl's critics often completely overlook the degree to which liberal use of the map/reduce paradigm can simplify the graphical representation of your code and allow the powerful list processing features to be brought to bear. Consider: use strict; use warnings; use List::Util qw/reduce/; map { print } join "\n", "Distribution of grades by letter:", map { sprintf( "\t%s: %s student%s", @$_, $_ -> [1] == 1 ? '' : 's' ) } map { my $c = $_ ; sort { $a -> [0] cmp $b -> [0] } map { [ $_, $c->{$_} ] } keys %$c } reduce { $a->{chr(ord($b->[1]))}++; $a } {}, map { printf( "List of students with failing grades:\n\t%s\n", join ', ' , map { $_->[0] } grep {ord $_->[1] >68} @$_); @$_} reduce {push(@$a, $b); $a} [], map { printf( "${^A}'s grade: %s\n" , $_ -> [1] ) if $_->[0] eq $^A; $_ } map { $^A="Zsófia"; [split(/\s+/)] } <STDIN> The use of strict and warnings making this particularly Modern Perl, you could almost be forgiven for thinking you were reading Haskell...
- Ultimatt 12y ago
  needs use feature 'say'

bglazer 12y ago

Could you elaborate a little? I ask because the Perl 5 code looks a lot like the Perl that I write. I'd like to improve, but the existing Perl code that I'm writing on top of is really bad. Like really, really bad. I don't have much quality Perl to compare against.

Mithaldu 12y ago
Two examples: $freq{substr $grade{$_}, 0, 1}++ for keys %grade; better: $freq{$_}++ for map { substr $_, 0, 1 } values %grade; best: my @letters = map { substr $_, 0, 1 } values %grade; $freq{$_}++ for @letters; ---------------------------- and open my $fh, '<:utf8', "grades.txt" or die "Failed to open file: $!"; my %grade; while (<$fh>) { m/^(\w+) \s+ ([A-F][+-]?)$/x or die "Can't parse line '$_'"; $grade{$1} = $2; }; better: use 5.010; use IO::All -binary, -utf8; my $line_format = qr/ ^ # line start (?<student>\w+) # name \s+ # gap (?<grade>[A-F][+-]?) # grade $ # line end /x; my $fh = io->file("grades.txt"); my %grade; while (my $line = $io->getline) { die "Can't parse line '$line'" if $line !~ $line_format; $grade{$+{student}} = $+{grade}; }
- hvs 12y ago
  Very nicely done. I use Perl in my everyday job, and its nice to see that some people still know how to write good Perl.
- Ultimatt 12y ago
  5.10 in production? Surely you're joking! 5.8 or bust.
- pjfl 12y ago
  You should have use strict; use warnings; then you would have noticed the my $fh and the $io->getline error
  - Mithaldu 12y ago
    Dammit, you're right. I was working in a buffer without perl instrumentation enabled because i was composing a comment, not a script. Now i can't edit the comment anymore. :/

peteretep 12y ago

Exactly. Perl's critics often completely overlook the degree to which liberal use of the map/reduce paradigm can simplify the graphical representation of your code and allow the powerful list processing features to be brought to bear. Consider: use strict; use warnings; use List::Util qw/reduce/; map { print } join "\n", "Distribution of grades by letter:", map { sprintf( "\t%s: %s student%s", @$_, $_ -> [1] == 1 ? '' : 's' ) } map { my $c = $_ ; sort { $a -> [0] cmp $b -> [0] } map { [ $_, $c->{$_} ] } keys %$c } reduce { $a->{chr(ord($b->[1]))}++; $a } {}, map { printf( "List of students with failing grades:\n\t%s\n", join ', ' , map { $_->[0] } grep {ord $_->[1] >68} @$_); @$_} reduce {push(@$a, $b); $a} [], map { printf( "${^A}'s grade: %s\n" , $_ -> [1] ) if $_->[0] eq $^A; $_ } map { $^A="Zsófia"; [split(/\s+/)] } <STDIN> The use of strict and warnings making this particularly Modern Perl, you could almost be forgiven for thinking you were reading Haskell...

Ultimatt 12y ago
needs use feature 'say'