Hi Peter,

Look at ERC.java.  It implements ephemeral random constants, which  
are almost what you are looking for.  Some minor modificiations  
should do the trick.

Keith


On Oct 1, 2008, at 5:55 AM, Peter Thieu wrote:

> Hi there
>
> i want leaves with a constant, i.e:
>
> public class Const extends GPNode
>   {
>     private int cValue;
>   public String toString() { return Integer.toString(this.cValue);}
>
>   public void checkConstraints(final EvolutionState state,
>                                final int tree,
>                                final GPIndividual typicalIndividual,
>                                final Parameter individualBase)
>       {
>       super.checkConstraints 
> (state,tree,typicalIndividual,individualBase);
>       if (children.length!=0)
>           state.output.error("Incorrect number of children for node  
> " +
>                              toStringForError() + " at " +
>                              individualBase);
>       }
>
>   public void eval(final EvolutionState state,
>                    final int thread,
>                    final GPData input,
>                    final ADFStack stack,
>                    final GPIndividual individual,
>                    final Problem problem)
>       {
>       DoubleData rd = ((DoubleData)(input));
>       this.cValue = ((int)(state.random[thread].nextDouble()*10));
>       rd.x = this.cValue;
>       }
>   }
>
> assuming it creates a tree like (x+2) * 3, where 2 and 3 leaves  
> were produced by the class Const
>
> assuming this tree is passed to the next generation, will it be the  
> same tree with the same constants (x+2) * 3, or will there be new  
> constants values i.e. (x+4) * 5?
>
> kind regards
>
> Peter