View source for Points with constraints (dup)

A point can depend on another geometric object. This dependence can be given by using JavaScript syntax or by using
GEONExT syntax. 
=== GEONExT syntax ===
Here is an example using GEONExT syntax.
The point A is draggable. The point B depends on point A: Its y-coordinate is set to 1 and its x-coordinate is set
to the x-coordinate of A.
<source lang="javascript">
var b = JXG.JSXGraph.initBoard('jxgbox1', {originX: 40, originY: 100, unitX: 40, unitY: 40});
var free = b.create('point',[0,0], {name:'A', style:5});
var dep = b.create('point',["X(A)",1], {name:'B', style:8});
</source>
<html>
<link rel="stylesheet" type="text/css" href="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraph.css" />
<script type="text/javascript" src="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraphcore.js"></script>
<div id="jxgbox1" class="jxgbox" style="width:600px; height:200px;"></div>
<script type="text/javascript">
var b = JXG.JSXGraph.initBoard('jxgbox1', {originX: 40, originY: 100, unitX: 40, unitY: 40});
var free = b.create('point',[0,0], {name:'A', style:5});
var dep = b.create('point',["X(A)",1], {name:'B', style:8});
</script>
</html>
=== JavaScript syntax ===
Now we do exactly the same with JavaScript syntax.
<source lang="javascript">
var b2 = JXG.JSXGraph.initBoard('jxgbox2', {originX: 40, originY: 100, unitX: 40, unitY: 40});
var free = b2.create('point',[0,0], {name:'A', style:5});
var dep = b2.create('point',[function(){ return free.X();}, 1], {name:'B', style:8});
</source>
<html>
<div id="jxgbox2" class="jxgbox" style="width:600px; height:200px;"></div>
<script type="text/javascript">
var b2 = JXG.JSXGraph.initBoard('jxgbox2', {originX: 40, originY: 100, unitX: 40, unitY: 40});
var free = b2.create('point',[0,0], {name:'A', style:5});
var dep = b2.create('point',[function(){ return free.X();}, 1], {name:'B', style:8});
</script>
</html>
The JavaScript syntax is much more robust against changes of the construction, but of course it looks more complicated.
Lets look at it again in detail:
First we construct a free, draggable point called "free".
<source lang="javascript">
var free = b2.create('point',[0,0], {name:'A', style:5});
</source>
Then we construct the dependent point "dep".
<source lang="javascript">
var dep = b2.create('point',[function(){ return free.X();}, 1], {name:'B', style:8});
</source>
The first coordinate of "dep" is given as an anonymous function:
<source lang="javascript">
function(){ return free.X();}
</source>
This function returns the x-coordinate of the point "free".


[[Category:Austragungsstueberl]]
Category:Examples