1.3 An Architectural Overview

These files need not all be generated on any particular FunnelWeb

run. Whether each output file appears, is controlled by command

line options.

FunnelWeb processes each input file in a sequence of phases. If an

error occurs during a phase, no subsequent phases are executed.

The phases are briefly described below.

The Scanner

 reads the input file, expands and reads

in include files, scans the input stream, processes

pragmas and typesetter directives, and parses all the

FunnelWeb special sequences. The result is a list of

tokens that is handed to the parser.

The Parser

 reads the scanner s token list and parses

it, constructing a document list and a macro table.

which are passed to later phases.

The Analyser

 examines the macro table generated by

the parser and performs a number of checks of the

macro structures that the parser could not make on its

single pass. For example, the analyser detects and

flags unused macros and recursive macros. The

analyser forms the final stage of FunnelWeb s

front end processing.

Tangle

 expands certain macros in the macro table to

generate one or more product files.

Weave

 uses the document list to generate a

documentation file.

A single run through these phases constitutes a single invocation of

FunnelWeb proper

. Most invocations of the 

FunnelWeb

program

 will consist only of a single execution of FunnelWeb

proper. However, FunnelWeb also provides a command shell that

provides many useful commands, including a command to invoke

FunnelWeb proper. Discussion of the command shell is deferred

until later.

Webmaster

Copyright   Ross N. Williams 1992,1999. All rights reserved.

http://www.ross.net/funnelweb/reference/intro_arch.html (2 of 2) [3/3/2000 10:49:26 PM]