postnet.scm: USPS POSTNET Barcode Encoding in Scheme

Version 0.2, 2005-07-12, http://www.neilvandyke.org/postnet-scm/

by Neil W. Van Dyke <neil@neilvandyke.org>

Copyright © 2004 - 2005 Neil W. 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.

Introduction

This postnet.scm Scheme library can be used to generate the United States Postal Service POSTNET barcode binary pattern, as described in Chapter 4 of USPS Publication 25, “Designing Letter and Reply Mail,” dated 2003-06. This library supports ZIP, ZIP+4, and DBPC codes.

The generated binary representation is a Scheme list of boolean values. Separate code must be written to render this representation to a particular printing devices.

Encoding

There are several procedures for encoding POSTNET from various input representations. It is suspected that most applications will encode from a string representation, using string->postnet.

— Procedure: digit-list->postnet digits

Yields a POSTNET encoding of a list of digit numbers. For example:

          (digit-list->postnet '(1 2 3 4 5))
          =>
          (#t #f #f #f #t #t #f #f #t #f #t #f #f #t #t #f
           #f #t #f #f #t #f #t #f #t #f #f #t #f #t #f #t)

— Procedure: char-list->postnet chars

Yields a POSTNET encoding of a list of characters. For example:

          (char-list->postnet '(#\1 #\2 #\3 #\4 #\5))
          =>
          (#t #f #f #f #t #t #f #f #t #f #t #f #f #t #t #f
           #f #t #f #f #t #f #t #f #t #f #f #t #f #t #f #t)

— Procedure: string->postnet str

Yields a POSTNET encoding of a string. For example:

          (string->postnet "12345-6789 01")
          =>
          (#t #f #f #f #t #t #f #f #t #f #t #f #f #t #t #f
           #f #t #f #f #t #f #t #f #t #f #f #t #t #f #f #t
           #f #f #f #t #t #f #f #t #f #t #f #t #f #f #t #t
           #f #f #f #f #f #f #t #t #f #t #f #f #t #t)

Debugging

Although this package does not render POSTNET for OCR use, for debugging purposes, the postnet->debug-string procedure can be used to approximate the barcode visually, using ASCII characters.

— Procedure: postnet->debug-string postnet

Yields a string visual approximation of a POSTNET encoding. For example:
          (postnet->debug-string (string->postnet "12345"))
          => "|...||..|.|..||..|..|.|.|..|.|.|"
     

Tests

The postnet.scm test suite can be enabled by editing the source code file and loading Testeez.

History

Version 0.2 — 2005-07-12: Added Testeez tests. Minor documentation changes.
Version 0.1 — 2004-04-14: Wrote as a diversion over dinner.