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Every leading substring that identifies one word out of a set and no other — the unambiguous prefixes a command-line tool lets you type instead of the whole subcommand.

Version

2.2.3 zef:tbrowder

Depends

nothing outside the core

License

Artistic-2.0

Its own test suite

9 files, green

Checked

2026-09-15 against Raku++ 3.28.0 and Rakudo 2026.08

Where it lives

raku.land · source

Install it #

$ rakupp install Abbreviations

zef install Abbreviations writes the same store; either installer leaves the module usable by both engines.

What it is for #

git ci is not a command; it is the shortest prefix of commit that no other subcommand shares, and the program worked out which. Doing that for your own word set is a small exercise in prefix trees that everyone writes badly once: for each word, every leading substring that matches it and nothing else. This distribution is that, with a choice of six shapes for the answer.

The shapes #

use Abbreviations;

my @months = <January February March April May June July>;

my %shortest = abbreviations(@months);
say %shortest.keys.sort.map({ "$_=" ~ %shortest{$_} }).join(' ');

say abbreviations(@months, :out-type(AL)).sort.join(' ');

my %by-abbrev = abbreviations(@months, :out-type(AH));
say %by-abbrev.elems, ' abbreviations in all';
say %by-abbrev<Ja>, ' ', %by-abbrev<Jul>, ' ', %by-abbrev<Marc>;

my %all = abbreviations(@months, :out-type(H));
say %all<April>.join(',');

April=A February=F January=Ja July=Jul June=Jun March=Mar May=May
A F Ja Jul Jun Mar May
27 abbreviations in all
January July March
A,Ap,Apr,Apri,April

The default shape, HA, maps each word to its shortest unambiguous prefix, which is the one a help message wants to show. AL is the same answers as a bare list. AH goes the other way, from every abbreviation to the word it selects, which is the table a command dispatcher looks a typed argument up in. H gives each word its full list, and S and L give everything as a string or a sorted list.

J appears in none of them: three months begin with it, so it identifies nothing and is not an abbreviation of anything. That is the whole point of the exercise.

Two options shape the answer rather than its container. :min-length raises the floor, so a set can be given prefixes that are all at least three characters. :lower-case folds the words first, which changes not just the case of the output but which prefixes are unambiguous.

The one thing to know #

With exactly one word in the set, :out-type is ignored and you get a pipe-delimited string instead of the hash or list you asked for:

use Abbreviations;

my $one = abbreviations(<solo>, :out-type(HA));
say $one.^name, ' ', $one.raku;

my %two = abbreviations(<solo duet>, :out-type(HA));
say %two.^name, ' ', %two.keys.sort.map({ "$_=" ~ %two{$_} }).join(' ');

say (try abbreviations((), :out-type(HA))) // $!.message;

Str "s|so|sol|solo"
Hash duet=d solo=s
FATAL: Empty input word set.

A caller that does %result{$word} on a word set that happens to have shrunk to one entry gets nonsense rather than an error, and the shape only changes back when a second word arrives. If the set is built at run time, check its size before trusting the return type. An empty set at least fails loudly.

One smaller thing worth knowing: sort-list, the companion that orders strings by length and then text, is not in the default export. It needs use Abbreviations :ALL;.