.- HTMLPP source for Perl, Code Generation, and State Machines talk
.- give at Wellington Perl Mongers meeting, 3 May 2000.
.-
.- By Ewen McNeill, iMatix Corporation (NZ) Limited.
.-
.define document Perl, Code Generation and State Machines
.define iMatix   http://www.imatix.com/
.define HTMLPP   http://www.imatix.com/html/htmlpp/
.define Otto     http://www.imatix.com/pub/tools/otto.zip
.define SrcDoc   http://www.imatix.com/pub/tools/srcdoc.zip
.define Libero   http://www.imatix.com/html/libero/
.define talkurl  http://www.imatix.co.nz/talks/codegen/
.define BASE index
.-
.include prelude.def
.page 

<CENTER>
<FONT SIZE=7 COLOR="Yellow">
<P>Code Generation, State Machines, and Perl
<FONT SIZE=5 COLOR="Yellow">
<P>Presented to the Wellington Perl Mongers Group
<P>&nbsp;
<FONT SIZE=4 COLOR="White">
<P>&nbsp;
<P>Ewen McNeill
<BR>3 May 2000


.page Overview

.H1 This presentation covers
.   H2 Code generation
.   H2 State machines
.   H2 ... and even a little Perl


.page What is code generation?

.H1 Code generation
.   H2 Makes &quot;common cases&quot; a template
.   H2 Lets you concentrate on the details
.   H2 Write more with less effort
.   H2 A blessing for the Larry Wall &quot;lazy programmer&quot;
.   H2 You're soaking in it (more on that in a moment)


.page How does code generation work?

<CENTER>
<IMG SRC="codegen.gif" WIDTH=473 HEIGHT=332>
</CENTER>

.page Soaking in code generation

.H1 This presentation was generated using $(*HTMLPP)
.   H2 A Perl based, Open Source, tool to generate HTML
.      H3 <A HREF="prelude.def">The document template</A>
.      H3 <A HREF="codegen.txt">Raw document information</A>
.      H3 <A HREF="runeg.txt">Example run of HTMLPP</A><!-- XXX: Need run!  -->


.page What are state machines?

.H1 State machines
.   H2 A Computer Science formalism
.   H2 A model for problems with distinct stages and actions
.   H2 Useful for
.      H3 Parsing computer languages
.      H3 Writing communications systems
.      H3 Modelling business processes

.page Implementing state machines

.H1 Several ways to implement state machines
.   H2 Explicit tests of states in the code 
.      H3 eg, a big case statement
.   H2 Manually written state tables
.   H2 Code generation


.page State machines and code generation

.H1 Code generation and state machines work well together
.   H2 Automates writing out the state logic
.   H2 Automates tracking and changing states
.   H2 Can include automatic exception processing
.   H2 Allows high level description of states


.page Libero: a state machine code generator

.H1 $(*Libero) by $(*iMatix)
.   H2 An Open Source state machine code generator
.   H2 Combines text description of states and template code
.      H3 eg, <A HREF="htmlpp.l">htmlpp.l</A>
.   H2 Generates state machine code in many languages
.      H3 Perl (<A HREF="lrschema.pl">template</A>) (<A HREF="htmlpp.d">generated code example</A>)
.      H3 C/C++ (<A HREF="lrschema.c">template</A>)
.      H3 Java (<A HREF="lrschema.jav">template</A>)


.page Libero: Putting it all together

.H1 Libero 
.   H2 Generates Perl code to track and change states
.   H2 Each state contains  (eg <A HREF="htmlpp.l">htmlpp.l</A>)
.      H3 Details for a series of events
.      H3 Functions to call when receiving that event in that state
.      H3 A new state to move to after the event
.   H2 You fill code for the functions, and indicate next event
.   H2 Your code is basically event based
.   H2 The generated code does the rest


.page Perl and Libero

.H1 $(*iMatix) have a number of Perl programs built using Libero
.   H2 $(*HTMLPP): A HTML generator
.   H2 $(*Otto): A build script generator
.   H2 $(*SrcDoc): Generate documentation from your source files


.page That's all folks

.H1 Summary
.   H2 Code generation: write boring repetitive code once
.   H2 State machines: a useful abstraction
.   H2 State machines and code generation work well together
.   H2 You can use both with Perl with ease
.H1 Questions?