<?xml version="1.0"?>

<!--
	description:

		"Gobo Eiffel Ant overview"

	library: "Gobo Eiffel Ant"
	copyright: "Copyright (c) 2003, Sven Ehrke and others"
	license: "MIT License"
	date: "$Date$"
	revision: "$Revision$"
-->

<chapter xmlns="http://www.gobosoft.com/eiffel/gobo/documentation" id="geant_overview">
<chapterinfo>
	<copyright>
		<year>2002-2005</year>
		<holder>Sven Ehrke</holder>
	</copyright>
	<author>
		<firstname>Sven</firstname><surname>Ehrke</surname>
	</author>
	<email>ericb@gobosoft.com</email>
	<date>7 July 2005</date>
</chapterinfo>

	<title>Overview of Geant</title>

	<para>
		Geant is a build tool specifically tailored for the Eiffel programming language.
	</para>

	<section id="introduction">
		<title>Why Geant?</title>

		<para>
			Like the build tool 'make', well known to C and C++ developers 'geant'
			is a build tool for Eiffel developers. It is based on the ideas of Jakarta Ant,
			a build tool for the Java programming language.
		</para>

		<para>
			There are several reasons why this build tool has been created. The first one
			is that I found it annoying to download interesting Eiffel libraries and
			having difficulties compiling and using them. Very often I gave up although
			I did spend quite some time trying to get it running. The frustrating thing in this
			situation is that you do not really know whether you just did anything wrong or if
			you simply had no chance to compile or use it since the software is not in
			a stable state. What I wanted to have is a build procedure and a readme file
			telling me how to invoke the build procedure so that I could use the software.
			If the build procedure failed I would know that it wasn't my fault and could send
			a bug report to the author.
		</para>

		<para>
			In the Java world there has been exactly the same problem. With the widespread use
			of Jakarta Ant the situation improved a lot. Having used Jakarta Ant for Java I thought
			it would be a good idea to have something similar for Eiffel and that's how Geant was born.
		</para>

		<para>
			Another advantage is that Geant is OS portable (tested on Windows, Linux, Solaris)
			and that it includes commands (so called tasks) which are tailored specifically for
			the usage with Eiffel. All available Eiffel compilers are supported.
		</para>

		<para>
			Reusability in build systems has always been an issue which wasn't addressed properly.
			Therefore Geant's build scripts can be used as classes: build scripts can inherit
			from other build scripts.
		</para>

	</section>

	<section>
		<title>How to invoke Geant</title>
		<para>
			Like other build tools geant is invoked on the commandline
			optionally followed by a so called targetname. Here are some examples (the $ sign
			represents the shell prompt):
		</para>

		<programlisting>
		  $ geant
		  $ geant help
		  $ geant compile
		</programlisting>

		<para>
			Geant then is looking for a file named 'build.eant' which contains the build instructions.
			So far all this sounds familiar to anyone who has used <emphasis>make</emphasis>.
			The first difference we encounter is that the format of 'build.eant' or generally
			eant files is XML. If you know Jakarta's Java build tool Ant you will see that the
			syntax is very similar.
		</para>

	</section>

	<section>
		<title>Diving into geant</title>
		<para>
			<link linkend="introduction">Introduction to geant</link>
		</para>
		<para>
			<link linkend="examples">geant examples</link>
		</para>
		<para>
			<link linkend="tasks">geant's tasks</link>
		</para>
		<para>
			<link linkend="builtin_variables">Built-in variables</link>
		</para>
	</section>
</chapter>
