author | deba |
Fri, 29 Sep 2006 11:23:54 +0000 | |
changeset 2222 | a24939ee343c |
child 2288 | ef8af928c54e |
permissions | -rw-r--r-- |
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/** |
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\page getting_started Getting Started |
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|
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At the beginning we hardly suggest that you open your favorite text editor |
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and enter the code simultaneously as you read it. Compiling the demos is also |
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a good exercise. |
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|
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As the first example we show you a lemon style "Hello World" program. Now we |
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explain almost every line, but later we will skip the basics and focus on new |
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things. |
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|
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\section hello_world Hello World in LEMON |
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|
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In this little program we give you a taste of the LEMON programming. |
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Let's see the code fragment to fragment! |
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\dontinclude hello_world.cc |
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\skip include |
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\until iostream |
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|
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We want to use a \c lemon::ListGraph so the include goes like this: |
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\skip include |
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\until list_graph |
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|
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The next few lines are not necessary but useful shortcuts, if you don't |
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want to type \c lemon::ListGraph::Node every time. |
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\skip using |
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\until Edge |
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|
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For this demo we need to declare a ListGraph and a special NodeMap to store the |
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characters associated to the graph's nodes. |
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\skip main |
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\until char_map |
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|
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Adding nodes to the graph is very easy. |
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\skip new_node |
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\until addNode |
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|
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When a new node or edge to the graph the assigned maps are automatically resized. |
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So graphs can be build dynamically. The usage of a map is very natural. |
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\skip char_map |
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\until char_map |
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|
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Notice that no reference or additional assignment needed to work with nodes. |
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They won't become illegal or won't lead to throwing any exceptions. |
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You can declare and handle node like every other basic type such as \c int. |
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\skip Store |
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\until char_map |
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|
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As one expects adding an Edge is similar. You need to define the \b source node |
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and the \b destination node. The nodes must belong to the graph of course. The |
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Edge has the direction from the source to the destination. In some case you don't |
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want the edges to be directed - then you use an undirected graph. For example |
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lemon::ListUGraph. |
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\skip addEdge |
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\until addEdge |
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|
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In the next few lines we add some more nodes and edges and to the graph we need. |
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Those lines are not very interesting so we skip them, but you find the whole |
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working program in file hello_lemon.cc in the demo section. |
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|
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The next statement must be familiar. But what is that INVALID in the \c while |
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test statement? In LEMON we usually use the INVALID to check if an object |
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contains valid information. |
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\skip current_node |
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\until { |
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|
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We take the current node and write out the character assigned to it. Is's easy |
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with the \c char_map. |
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\skip std |
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\until std |
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|
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And here comes the trick. OutEdgeIt iterates on outgoing edges of a given node. |
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We pass the current node as argument to it, so the \c edge iterator will stand |
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on the first outgoing edge of the current node, or will be INVALID if the node |
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has no outgoing edges. |
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\skip edge |
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\until edge |
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|
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The graph we built before is linear, so we know that it ends, when no more outgoing |
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edges found. Otherwise the current node must be the node the edge points to. |
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Basic information about an edge can be requested from the graph. |
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\skip if |
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\until } |
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|
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Finish the code, just to be precise. |
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\skip return |
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\until } |
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|
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|
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\section compile_hw Compiling Hello World |
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To compile this program all you have to do is type in |
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\code g++ -ohw hello_world.cc \endcode |
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and press \c Enter! This is the case if you installed LEMON on your system. |
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(For more information see the LEMON installation instructions.) |
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|
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This is because LEMON is template library and most of it's code has to be available |
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as source code during compilation. |
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|
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Most programs using LEMON will compile as easy as this one unless you want to |
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use some performance measuring tools LEMON can provide. Then you need to link |
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an additional library against your program. |
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*/ |