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Package org.jenetics.prog.op


See: Description

Package org.jenetics.prog.op Description


When creating a new program tree, it is not necessary to implement own instance of the ProgramGene or ProgramChromosome class. The extension point for own programs is the Op interface.
public interface Op<T> { public String name(); public int arity(); public T apply(T[] args); }
final Op<Double> myop = Op.of("myop", 3, v -> v[0]*v[1] + v[2]);
In the example above, a new operation with the "myop" and arity 3 is defined. Whenever the operation is evaluated, the function f(x, y, z) = x*y + z is executed.

NOTE: The class MathOp in the defines a set of mathematical standard operations/functions.

When creating a new ProgramChromosome we must distinguish two different kind of operations:
  1. Non-terminal operations have an arity greater than zero and form their own sub-tree
  2. Terminal operations have an arity of zero and form the leaves of a program tree.
There are currently three different types of non-terminal operations implemented, Var, Const and EphemeralConst.


The Var operation defines a variable of a program, which are set from the program arguments.
final ISeq<Op<Double>> terminals = ISeq.of( Var.of("x", 0), Var.of("y", 1), Var.of("z", 2) );
The terminal operation list in the example code above will lead to a program which takes three input parameters, x, y and z, with the argument indices 0, 1 and 2.


The Const operation will always return the same, constant, value when evaluated.
final Op<Double> one = Const.of(1.0); final Op<Double> pi = Const.of("π", Math.PI);
We can create a constant operation in to flavours, with a value only and with a dedicated name. If a constant has a name, the symbolic name is used, instead of the value, when the program tree is printing.


An ephemeral constant is a special constant, which is only constant within an tree. If a new tree is created, a new constant is created, by the ` Supplier function the ephemeral constant is created with.
final Op<Double> rand1 = EphemeralConst.of(Math::random); final Op<Double> rand2 = EphemeralConst.of("R", Math::random);
Franz Wilhelmstötter
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© 2007-2017 Franz Wilhelmstötter  (2017-08-22 19:30)