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Turn a list into a natural-language phrase — a, b, and c — with control over the conjunction, the Oxford comma, the separator and the language.

Version

1.3 zef:raku-community-modules

Depends

none beyond the core

License

Artistic-2.0

Its own test suite

1 file, green

Checked

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

Where it lives

raku.land · source

Install it #

$ rakupp install Lingua::Conjunction

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

What it is for #

@items.join(', ') gives you apples, oranges, pears, which is not what a person writes. What a person writes is apples, oranges, and pears — with no comma at all when there are two items, and no conjunction when there is one.

Getting that right is four special cases, and every program that reports to a human needs it.

Building a phrase #

use Lingua::Conjunction;

for ('apples',), <apples oranges>, <apples oranges pears>, <a b c d> -> @l {
    say sprintf('%-34s => %s', @l.raku, conjunction(|@l));
}
say '';
say 'type => or  : ', conjunction(<a b c>, :type<or>);
say 'type => and : ', conjunction(<a b c>, :type<and>);

("apples",)                        => apples
("apples", "oranges")              => apples and oranges
("apples", "oranges", "pears")     => apples, oranges, and pears
("a", "b", "c", "d")               => a, b, c, and d

type => or  : a, b, or c
type => and : a, b, and c

One item comes back unchanged, two get a bare conjunction with no comma, three or more get the Oxford comma. That is the English convention, and it is four branches you no longer have to write.

The switches #

use Lingua::Conjunction;

say 'default          : ', conjunction(<a b c>);
say ':last (Oxford)   : ', conjunction(<a b c>, :last);
say ':!last (no comma): ', conjunction(<a b c>, :!last);
say '';
say 'a template       : ', conjunction(<a b c>, :str('I want |list| today'));
say '';
say 'empty list       : ', conjunction().raku;
say 'one item         : ', conjunction('solo').raku;

default          : a, b, and c
:last (Oxford)   : a, b, and c
:!last (no comma): a, b and c

a template       : I want a, b, and c today

empty list       : ""
one item         : "solo"

:last controls the serial comma. The :str template drops the phrase into a sentence, which saves an interpolation.

The empty list returns "" and a single item returns itself — neither is an error, which is worth knowing if you expect the conjunction word to always be there.

Other languages #

use Lingua::Conjunction;

for <en fr es de> -> $lang {
    say sprintf('%-4s => %s', $lang, conjunction(<a b c>, :$lang));
}

en   => a, b, and c
fr   => a, b et c
es   => a, b, y c
de   => a, b, und c

French drops the serial comma, Spanish and German keep it. The language table is small; ja is present and produces a doubled space where the conjunction should be, so treat anything beyond these four as untested.

The one thing to know #

An item that already contains the separator silently changes the separator for the whole list.

use Lingua::Conjunction;

say 'ordinary items  : ', conjunction(<toast jam tea>);
say 'one item has a comma in it:';
say '  ', conjunction('eggs, bacon', 'toast', 'jam');
say '';
say 'the alternate separator is ; by default, and :alt changes it:';
say '  ', conjunction('eggs, bacon', 'toast', 'jam', :alt(' / '));

ordinary items  : toast, jam, and tea
one item has a comma in it:
  eggs, bacon; toast; and jam

the alternate separator is ; by default, and :alt changes it:
  eggs, bacon /  toast /  and jam

Linguistically this is the right call — a comma-separated list of items that themselves contain commas is unreadable — and it is clearly deliberate. What it means in practice is that the shape of the output depends on the content of the data: the same call site produces a, b, and c for one dataset and a; b; and c for another.

Anything that parses, splits or tests the result against a fixed separator works until a user types a comma.

Where the two engines differ #

Only on stderr, and only for some inputs: Rakudo emits Use of Nil in string context from line 38 of the module where Raku++ is silent. Every phrase in this page was byte-identical.

The switch worth knowing about and not using: :lang<ja> emits an empty conjunction word, so conjunction(<a b c>, :lang<ja>) comes back as a, b c with a doubled space. The four European languages above are the ones that work.