noweb

Noweb

Original author(s)	Norman Ramsey
Initial release	1989, 21–22 years ago
Stable release	2.11b
Written in	C
Operating system	Cross-platform
Available in	English
Type	Literate programming
Website	http://www.cs.tufts.edu/~nr/noweb/

noweb is a literate programming tool, created in 1989–1999 by Norman Ramsey^[1], and designed to be simple, easily extensible and language independent.

As in WEB and CWEB, the main components of noweb are two programs: "notangle", which extracts 'machine' source code from the source texts, and "noweave", which produces nicely-formatted printable documentation.

noweb supports TeX, LaTeX, HTML, and troff back ends and works with any programming language. Besides simplicity this is the main advantage over WEB, which needs different versions to support programming languages other than Pascal. (Thus the necessity of CWEB, which supports C and similar languages.)

Noweb's input

A noweb input text contains program source code interleaved with documentation. It consists of so-called chunks that are either code-chunks or documentation-chunks.

It uses LaTeX code for documentation chunks, but you may easily use any form you like.

Code-chunks aren't treated specially by noweb's tools – they may be placed in any order and when needed, they are just concatenated, chunk-references in code are dereferenced and the whole requested source code is extracted.

A code-chunk consists of at least 3 lines: The declaration, the contents and the terminating @. Smaller chunks cannot be reduced onto single lines.

Example of a simple noweb program

This is an example of a "hello world" program with documentation:

@
\section{Hello world}

Today I awoke and decided to write
some code, so I started to write Hello World in \textsf C.

<<hello.c>>=
/*
  <<license>>
*/
#include <stdio.h>

int main(int argc, char *argv[]) {
  printf("Hello World!\n");
  return 0;
}
@
\noindent \ldots then I did the same in PHP.

<<hello.php>>=
<?php
  /*
  <<license>>
  */
  echo "Hello world!\n";
?>
@
\section{License}
Later the same day some lawyer reminded me about licenses.
So, here it is:

<<license>>=
This work is placed in the public domain.
@

Assuming that the above code is placed in a file named 'hello.nw', the command to extract the human-readable document in HTML format is:

noweave -filter l2h -index -html hello.nw | htmltoc > hello.html

... and in LaTeX format:

noweave -index -latex hello.nw > hello.tex

To extract machine source code:

notangle -Rhello.c hello.nw > hello.c

notangle -Rhello.php hello.nw > hello.php

Compatibility

noweb defines a specific file format and a file is likely to interleave three different formats (noweb, latex and the language used for the software). This is not recognised by other software development tools and consequently using noweb excludes the use of UML or code documentation tools.

See also

• WEB
• CWEB

Notes

1. ^ Author's site

External links

• Noweb home page
• Norman Ramsey's home page
• notangle online man page
• noweb.py – an open-source noweb clone written in Python
• noweb.php – noweb clone in PHP