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anagrams.raku

Groups words into anagram classes.

Two words are anagrams when they share the same multiset of letters, so each word is keyed by its letters sorted into order (.comb.sort.join) and .classify drops matching words into the same bucket. The non-trivial groups are printed largest-first, ties broken by key so the output never changes.

The program

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#!/usr/bin/env raku
# Anagram classes. Two words are anagrams when they are the same multiset of
# letters, so the trick is to give every word a canonical key — its letters
# sorted into order — and let words with the same key fall into the same
# bucket. `.classify` does exactly that grouping; the rest is string ops
# (`.comb.sort.join`) and a deterministic sort of the buckets for printing.

my @words = <
    listen silent enlist tinsel   evil live vile veil
    stop tops pots spot opts post  night thing
    cat act tac                    angle glean angel
    dog god                        rat tar art
    cab bac                        stressed desserts
>;

# The canonical key: sort a word's letters. "listen" and "silent" both map
# to "eilnst", so `.classify` drops them into the same group.
my %groups = @words.classify(*.comb.sort.join);

say "Anagram groups (largest first):";
say '';

# Keep only the real anagram groups (two or more words), and print them
# biggest-first, breaking ties by key so the output is always the same.
for %groups.pairs.sort({ $^b.value.elems <=> $^a.value.elems
                         || $^a.key leg $^b.key }) -> $group {
    next if $group.value.elems < 2;
    printf "  %-9s  %s\n", $group.key, $group.value.sort.join(' ');
}

say '';
my $classes = %groups.pairs.grep(*.value.elems >= 2).elems;
say "Found $classes anagram classes among {@words.elems} words.";

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Anagram groups (largest first):

  opst       opts post pots spot stop tops
  eilnst     enlist listen silent tinsel
  eilv       evil live veil vile
  act        act cat tac
  aegln      angel angle glean
  art        art rat tar
  abc        bac cab
  deerssst   desserts stressed
  dgo        dog god
  ghint      night thing

Found 10 anagram classes among 31 words.

Feature focus: hashes, .classify.