File: groff.info,  Node: Preprocessor Intro,  Next: Output Device Intro,  Prev: Macro Package Intro,  Up: Introduction

1.5 Preprocessors
=================

An alternative approach to complexity management, particularly when
constructing tables, setting mathematics, or drawing diagrams, lies in
preprocessing.  A "preprocessor" employs a domian-specific language to
ease the generation of tables, equations, and so forth in terms that are
convenient for human entry.  Each preprocessor reads a document and
translates the parts of it that apply to it into GNU 'troff' input.
Command-line options to 'groff' tell it which preprocessors to use.

   'groff' provides preprocessors for laying out tables ('gtbl'),
typesetting equations ('geqn'), drawing diagrams ('gpic' and 'ggrn'),
inserting bibliographic references ('grefer'), and drawing chemical
structures ('gchem').  An associated program that is useful when dealing
with preprocessors is 'gsoelim'.(1)  (*note Preprocessor
Intro-Footnote-1::)

   'groff' also supports 'grap', a preprocessor for drawing graphs.  A
free implementation of it can be obtained separately.

   Unique to 'groff' is the 'preconv' preprocessor that enables 'groff'
to handle documents in a variety of input encodings.

   Other preprocessors exist, but no free implementations are known.  An
example is 'ideal', which draws diagrams using a mathematical constraint
language.