Case Insensitive Unique Array Elements in Perl

perl, uniq

Solution

Use lowercase, `lc` with a `map` statement:

my @uniq_no_case = uniq map lc, @elements;

The reason `List::MoreUtils'` `uniq` is case sensitive is that it relies on the deduping characteristics of hashes, which also is case sensitive. The code for `uniq` looks like so:

sub uniq {
    my %seen = ();
    grep { not $seen{$_}++ } @_;
}

If you want to use this sub directly in your own code, you could incorporate `lc` in there:

sub uniq_no_case {
    my %seen = ();
    grep { not $seen{$_}++ } map lc, @_;
}

Explanation of how this works:

`@_` contains the args to the subroutine, and they are fed to a `grep` statement. Any elements that return true when passed through the code block are returned by the grep statement. The code block consist of a few finer points:

- `$seen{$_}++` returns 0 the first time an element is seen. The value is still incremented to 1, but after it is returned (as opposed to `++$seen{$_}` who would inc first, then return).

- By negating the result of the incrementation, we get true for the first key, and false for every following such key. Hence, the list is deduped.

- `grep` as the last statement in the sub will return a list, which in turn is returned by the sub.

- `map lc, @_` simply applies the `lc` function to all elements in `@_`.

Problem

I am using the uniq function exported by the module, List::MoreUtils to find the uniq elements in an array. However, I want it to find the uniq elements in a case insensitive way. How can I do that? I have dumped the output of the Array using Data::Dumper: ``` #! /usr/bin/perl use strict; use warnings; use Data::Dumper qw(Dumper); use List::MoreUtils qw(uniq); use feature "say"; my @elements=<array is formed here>; my @words=uniq @elements; say Dumper \@words; ``` Output: ``` $VAR1 = [ 'John', 'john', 'JohN', 'JOHN', 'JoHn', 'john john' ]; ``` Expected output should be: john, john john Only 2 elements, rest all should be filtered since they are the same word, only the difference is in case. How can I remove the duplicate elements ignoring the case?

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