Distribution · linguistics

Lingua::Lipogram

Works

Does this text avoid all of these letters? — one multi with five candidates, where <ch> and ('ch',) mean completely different things.

Version: 0.1.0 github:sfischer13
Depends: Pod::To::Text (declared, unused, and not in the ecosystem index)
License: MIT
Its own test suite: 3 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 Lingua::Lipogram

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

What it is for #

A lipogram is a text written without some letter. Georges Perec's La Disparition is a novel with no e in it; constrained-writing puzzles and word games are full of smaller ones. The question the form asks is always the same: does this text avoid all of these characters?

This distribution answers exactly that question, case-insensitively, for a string or for a file.

Asking #

File

use Lingua::Lipogram;

say 'no "e" in "Lingua"      : ', lipogram('Lingua', 'e');
say 'but "e" is in "letter"  : ', lipogram('letter', 'e');
say 'case is folded          : ', lipogram('Elephant', 'e');
say '';
say 'several letters at once :';
say '  lipogram("rhythm", "aeiou") = ', lipogram('rhythm', 'aeiou');
say '  lipogram("syzygy", "aeiou") = ', lipogram('syzygy', 'aeiou');
say '';
say 'a Range works too       :';
say '  lipogram("xyz",  "a".."c") = ', lipogram('xyz',  'a'..'c');
say '  lipogram("xayz", "a".."c") = ', lipogram('xayz', 'a'..'c');

Output

no "e" in "Lingua"      : True
but "e" is in "letter"  : False
case is folded          : False

several letters at once :
  lipogram("rhythm", "aeiou") = True
  lipogram("syzygy", "aeiou") = True

a Range works too       :
  lipogram("xyz",  "a".."c") = True
  lipogram("xayz", "a".."c") = False

An empty letter set is vacuously true:

File

use Lingua::Lipogram;

say q{lipogram('anything', '')  = }, lipogram('anything', '');
say q{lipogram('anything', ())  = }, lipogram('anything', ());
say '';
say 'the five candidates take (Str|IO::Path) x (Str|Range|Positional),';
say 'minus the IO::Path + Positional combination, which does not exist.';

Output

lipogram('anything', '')  = True
lipogram('anything', ())  = True

the five candidates take (Str|IO::Path) x (Str|Range|Positional),
minus the IO::Path + Positional combination, which does not exist.

From a file #

File

use Lingua::Lipogram;

my $f = $*TMPDIR.add("lipogram-{$*PID}.txt");
LEAVE $f.unlink;
$f.spurt("A quick brown fox jumps over a lazy dog.\n");

say 'no "z" in the file ? ', lipogram($f, 'z');
say 'no "o" in the file ? ', lipogram($f, 'o');
say '';
say 'there is no IO::Path + list candidate — only Str and Range:';
my $r = try lipogram($f, ('ing',));
say '  lipogram($path, ("ing",)) -> ', $! ?? 'no candidate matches' !! $r;
say '  slurp it yourself for the list form.';

Output

no "z" in the file ? False
no "o" in the file ? False

there is no IO::Path + list candidate — only Str and Range:
  lipogram($path, ("ing",)) -> no candidate matches
  slurp it yourself for the list form.

The one thing to know #

The Str argument is a set of single letters; the Positional argument is a set of substrings. And <ch> is a Str, not a list — so the natural spelling means something completely different from what it looks like.

File

use Lingua::Lipogram;

say '<ch> is a ', <ch>.WHAT.^name, ', <ch ap> is a ', <ch ap>.WHAT.^name;
say '';
say 'lipogram("the cap", <ch>)      = ', lipogram('the cap', <ch>),
    '   <- forbids "c" and "h" SEPARATELY, and both are present';
say 'lipogram("the cap", ("ch",))   = ', lipogram('the cap', ('ch',)),
    '   <- forbids the SUBSTRING "ch", which is absent';
say '';
say 'so a one-element angle list silently switches you from "no digraph"';
say 'to "neither of these two letters". Write ("ch",) or ["ch"].';

Output

<ch> is a Str, <ch ap> is a List

lipogram("the cap", <ch>)      = False   <- forbids "c" and "h" SEPARATELY, and both are present
lipogram("the cap", ("ch",))   = True   <- forbids the SUBSTRING "ch", which is absent

so a one-element angle list silently switches you from "no digraph"
to "neither of these two letters". Write ("ch",) or ["ch"].

Where the two engines differ #

Nothing in the library. The distribution ships a bin/lipogram script that declares a dependency on Pod::To::Text, and that is where the engines part: Rakudo bundles it in core, Raku++ does not, so the script dies there with Could not find Pod::To::Text while the module itself — which never uses it — is unaffected on both.

File

use Lingua::Lipogram;

# the module is pure and portable; only the shipped script is not
my $perec = 'Un long fauteuil, un tapis, un mur blanc';
say 'text : ', $perec;
say '  avoids "e" ?      ', lipogram($perec, 'e');
say '  avoids "aeiou" ?  ', lipogram($perec, 'aeiou');
say '';
say 'and the inverse question, which this module does not answer —';
say 'which forbidden letters actually occur — is one grep away:';
say '  offenders : ',
    'aeiou'.comb.grep({ !lipogram($perec, $_) }).join(' ');

Output

text : Un long fauteuil, un tapis, un mur blanc
  avoids "e" ?      False
  avoids "aeiou" ?  False

and the inverse question, which this module does not answer —
which forbidden letters actually occur — is one grep away:
  offenders : a e i o u