Version 0.1, 2006-05-07, http://www.neilvandyke.org/numspell-scm/
Neil Van Dyke
Copyright © 2006 Neil Van Dyke. This program is Free Software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose. See <
http://www.gnu.org/copyleft/lesser.html> for details. For other license options and consulting, contact the author.
numspell.scm library provides the ability to “spell” Scheme
numbers in English. This is useful for writing numbers on banking checks
and other legal documents, as well as for speech generation.
Most rational numbers in Scheme are presently supported. For example:
(number->english 123456) => "one hundred twenty-three thousand four hundred fifty-six" (number->english (/ 4 -6)) => "negative two over three" (number->english (exact->inexact (/ 4 -6))) => "negative zero point six six six six six six" ; approx.
The number names supported by
numspell.scm are taken from a version
of the Wikipedia “Names of large numbers” article. Both
short and long scales are supported, through different procedures, with short scale being
the default. For example:
(number->english (expt 10 15)) => "one quadrillion" (number->short-scale-english (expt 10 15)) => "one quadrillion" (number->long-scale-english (expt 10 15)) => "one thousand billion"
Note: Some numbers, such as very large and very small non-integers printed
by some Scheme implementations in exponential notation, are not supported
by the current version of
numspell.scm requires R5RS, SRFI-6 (string ports), and SRFI-11
The public interface consists of a few procedures.
Spell number num to output port port. If num cannot be spelt, an error is signaled.
Yield a string that spells number num. If num cannot be spelt, an error is signaled.
numspell.scm test suite can be enabled by editing the source
code file and loading Testeez.