source: lemon-tutorial/getting_started.dox @ 9:a48bf0d3a790

/* -*- mode: C++; indent-tabs-mode: nil; -*-
 *
 * This file is a part of LEMON, a generic C++ optimization library.
 *
 * Copyright (C) 2003-2008
 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
 * (Egervary Research Group on Combinatorial Optimization, EGRES).
 *
 * Permission to use, modify and distribute this software is granted
 * provided that this copyright notice appears in all copies. For
 * precise terms see the accompanying LICENSE file.
 *
 * This software is provided "AS IS" with no warranty of any kind,
 * express or implied, and with no claim as to its suitability for any
 * purpose.
 *
 */

/**
\page hello_lemon Compile Your First Code

If you have installed LEMON on your system you can paste the following
code segment into a file called <tt>hello_lemon.cc</tt> to have a first
working program that uses LEMON.

\dontinclude hello_lemon.cc
\skip #include
\until }

First let us briefly explain how this example program works.
(The used notions will be discussed in detail in the following sections.)

After some convenience typedefs we create a directed graph (\e digraph)
and add some nodes and arcs to it.
ListDigraph is one of the digraph classes implemented in LEMON.
It is based on linked lists, therefore iterating through its nodes and
arcs is fast.

Then we iterate through all nodes of the digraph and print their unique
IDs. We use a constructor of the node iterator to initialize it to the
first node.
The <tt>operator++</tt> is used to step to the next node. After the last
node the iterator becomes invalid (i.e. it is set to \c INVALID).
This is what we exploit in the stop condition.
We iterate through all arcs of the digraph very similarly and print the
IDs of their source (tail) and target (head) nodes using the \c source()
and \c target() member functions.

After that we create an arc map, which is actually a mapping that assigns
an \c int value (length) to each arc, and we set this value for each arc.
Finally we iterate through all arcs again and print their lengths.

Now let us compile this simple example program.

\section hello_lemon_system If LEMON is Installed System-Wide

If LEMON is installed system-wide (into directory \c /usr/local),
then it is very easy to compile this program with the
following command (the argument <tt>-lemon</tt> tells the compiler
that we are using the installed LEMON):

\verbatim
g++ -lemon hello_lemon.cc -o hello_lemon
\endverbatim

As a result you will get the exacutable \c hello_lemon in the current
directory, which you can run by the following command.

\verbatim
./hello_lemon
\endverbatim

\section hello_lemon_user If LEMON is Installed User-Local

Compiling the code is a bit more difficult if you installed LEMON
user-local into a directory (e.g. <tt>~/lemon</tt>) or if you just
skipped the step <tt>make install</tt>.
You have to issue a command like this.

\verbatim
g++ -lemon -I ~/lemon -L ~/lemon/lemon/.libs hello_lemon.cc -o hello_lemon
\endverbatim

If everything has gone well, then our program prints out the followings.

\verbatim
Hello World!
This is LEMON library here. We have a direceted graph.

Nodes: 3 2 1 0
Arcs: (2,3) (1,3) (1,2) (0,2) (0,1)

There is a map on the arcs (length):

length(2,3)=10
length(1,3)=25
length(1,2)=5
length(0,2)=20
length(0,1)=10
\endverbatim

You may note that iterating through the nodes and arcs is done in the
reverse order compared to the creating order (the IDs are in decreasing
order).
This is due to implementation aspects, that may differ at other graph
types, moreover it may be changed in the next releases.
Thus you should not exploit this method in any way, you should not
suppose anything about the iteration order.

If you managed to compile and run this example code without any problems,
you can go on reading this tutorial to get to know more features and tools
of LEMON.
Otherwise if you encountered problems that you did not manage to solve,
do not hesitate to
<a href="mailto:lemon-user@lemon.cs.elte.hu"><b>contact us</b></a>.

*/