---
name: "nowebfilters"
section: "7"
platform: "linux"
package: "noweb"
version: "2.13-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/nowebfilters"
---

# nowebfilters(7)

filters and parsers for use with noweb

## NAME

nowebfilters - filters and parsers for use with noweb

## SYNOPSIS

\[**noweave**\|**notangle**\|**noweb**\] \[**-filter** *filter*\|**-markup** *parser*\] ...

## DESCRIPTION

This man page documents the various filters and parsers that are  supplied with  [*noweb*(1)](/noweb/1.md). A filter, which transforms the pipeline representation, is used with the **-filter** option. A parser, which reads a source file and emits the pipeline representation, is used with the **-markup** option. Not all filters and parsers are available at all installations.

## FILTERS

- **autodefs.\***

  *noweave's* **-autodefs** and  **-showautodefs** options use these filters, which automatically find defined identifiers. The  **\*** stands for the name of a programming language. (Icon installation only.)

- **btdefn**

  The **btdefn** filter uses Dave Hanson's convention to mark definitions. In code chunks, each defining instances of an identifier should be preceded by  a single backtick character (ASCII 140). The **btdefn** filter removes these backticks from the code and converts them to definitions, thus: **\`definition**. It, not **@ %def**, should be used with both  [*notangle*(1)](/notangle/1.md) and [*noweave*(1)](/noweave/1.md), at least for programs written in C-like languages.

- **disambiguate**

  The  **disambiguate** filter makes it possible to abbreviate chunk names using a trailing ellipsis (three periods), in the style of WEB and  *nuweb*(1).

- **docs2comments** *options*

  The **docs2comments** filter converts documentation chunks to comments in code chunks. Options include  **-all**, which converts all documentation chunks into comments; **-one** converts only one documentation chunk preceding each code chunk. The **-w***k* option formats comments  *k* columns wide.

-

  Other options control the language and style of the comment. Languages available include **-awk**, **-c**, **-c++**, **-f77**, **-f90**, **-icn**, **-icon**, **-lisp**, **-m3**, **-ml**, **-ocamlweb**, **-pascal**, **-scm**, and **-tex**.

-

  Norman recommends using [**notangle**(1)](/notangle/1.md) with **docstocomments** instead of [**nountangle**(1)](/nountangle/1.md). (Icon installation only.)

- **elide *patterns***

  The **elide** filter removes from the stream any code chunk matching  any of the arguments. Each argument is a pattern in which **?** matches any single character and **\* matches any sequence of characters.**

- **emptydefn**

  The  **emptydefn** filter makes an empty definition (**\<\<\>\>=**) an abbreviation for a continuation of the previous definition.

- **l2h** \[**-show-unknowns**\] \[**-html-quotes**\]

  The  **l2h** filter converts LaTeX to HTML in documentation chunks. If the **-show-unknowns** options is given, unrecognized LaTeX control sequences appear in bold in the output. If the **-html-quotes** option is given,  **l2h** converts LaTeX double-quote ligatures into HTML 4 double-quote entities. **l2h** uses the LaTeX-generated .toc and .bbl files to help create table of contents and bibliography. (Icon installation only.)

- **pipedocs *command***

  The  **pipedocs** filter runs each documentation chunk through an invocation of *command*, which may be any Unix command. The Noweb library includes the command **h2a**, which uses  [*lynx*(1)](/lynx/1.md) to convert HTML to  ASCII.

- **xchunks** *files*

  The  **xchunks** filter pulls in code chunks from an external source. The *files* argument lists one or more noweb files, which are used only for their  definitions of code chunks. Empty chunk definitions in the main document are replaced with  the external definitions of the same name. This filter makes it possible to include the same code chunks  in multiple documents, or even the same code chunks multiple  times in the same document. (Icon installation only.)

## PARSERS

A parser converts a source file to the noweb pipeline format, interpreting the \`\`markup'' in that file. By default, the tools use the standard noweb markup, but some installations may support nuweb markup as well. Parsers include

- **markup**

  Converts standard [*noweb*(1)](/noweb/1.md) markup to pipeline format.

- **numarkup**

  Converts  *nuweb*(1) markup to noweb pipeline format. It is not part of the standard installation, but it can be found in *noweb*'s  **contrib/norman** directory.

## FILES

All filters and parsers are stored in **/usr/lib/noweb**

## BUGS

It is possible to tell **l2h** about new control sequences by putting special TeX comments in one's  documentation chunks, but there's no documentation. Use the source, Luke.

**numarkup** loses information, e.g., about the proper treatment of tabs. It also doesn't compensate for *notangle*'s newline-removal heuristic, which means results on  *nuweb* files may differ subtly from those produced by  *nuweb.*

Many filters are not available in installations that use Awk instead of Icon.

## SEE ALSO

[*noweave*(1)](/noweave/1.md), [*notangle*(1)](/notangle/1.md), [*noweb*(1)](/noweb/1.md)\
 The *Noweb Hacker's Guide*

## VERSION

This man page is from  *noweb* version 2.12.

## AUTHOR

Norman Ramsey, Tufts University. Internet address **Norman.Ramsey@tufts.edu**.\
 Noweb home page at **http://www.cs.tufts.edu/~nr/noweb**.