Two One-Liners and Short Programs: Weekly Challenge #230
We are at Weekly Challenge #230, and my children would like to remind you that this is a great time to schedule a dentist appointment. (“Tooth hurty”)
Task 1: Separate Digits
Submitted by: Mohammad S Anwar
You are given an array of positive integers.Write a script to separate the given array into single digits.
Let’s Talk About It
Today’s challenges seem to be very easily handled with one-liner functional solutions. In this case, we split each number into digits and retain order, so map and split does it. @output = map { split $_, // } @input. This is not a true Perl one-liner, but the functional programming tools provides allows for an expression rather than a subroutine.
Here it is as a one-liner:
perl -E 'say join q{, }, map {split //} @ARGV' 1 34 5 6
1, 3, 4, 5, 6
(It could be done better, I’m sure. I don’t like going to one-liners as a general rule.)
Show Me The Code
#!/usr/bin/env perl
use strict;
use warnings;
use experimental qw{ say postderef signatures state };
use List::Util qw( sum0 );
my @examples = (
[1, 34, 5, 6],
[1, 24, 51, 60],
);
for my $e (@examples) {
my @input = $e->@*;
my $input = join ', ', @input;
my @output = map { split //, $_ } @input;
my $output = join ', ', @output;
say <<~"END";
Input: \@ints = ($input)
Output: ($output)
END
}
$ ./ch-1.pl
Input: @ints = (1, 34, 5, 6)
Output: (1, 3, 4, 5, 6)
Input: @ints = (1, 24, 51, 60)
Output: (1, 2, 4, 5, 1, 6, 0)
Task 2: Count Words
Submitted by: Mohammad S Anwar You are given an array of words made up of alphabetic characters and a prefix.
Write a script to return the count of words that starts with the given prefix.
Let’s Talk About It
Here I separate out the work into a subroutine, but that subroutine has two lines, so I could’ve easily done the same as before and done the work inside the loop, with scalar and grep rather than map and split.
Show Me The Code
#!/usr/bin/env perl
use strict;
use warnings;
use experimental qw{ say postderef signatures state };
use List::Util qw( uniq );
my @examples = (
{
words => [ "pay", "attention", "practice", "attend" ],
prefix => "at"
},
{
words => [ "janet", "julia", "java", "javascript" ],
prefix => "ja"
},
);
for my $e (@examples) {
my $prefix = $e->{prefix};
my @input = $e->{words}->@*;
my $input = join ', ', map {qq{"$_"}} @input;
my $output = count_words($e);
say <<~"END";
Input: \@words = ($input)
\$prefix = "$prefix"
Output: $output
END
}
sub count_words ($ref) {
my $prefix = $ref->{prefix};
return scalar grep { $_ =~ /^$prefix/ } $ref->{words}->@*;
}
$ ./ch-2.pl
Input: @words = ("pay", "attention", "practice", "attend")
$prefix = "at"
Output: 2
Input: @words = ("janet", "julia", "java", "javascript")
$prefix = "ja"
Output: 3