Package io.jenetics.prog.op

Operations

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.

Var

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.

Const

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.

EphemeralConst

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);

Since:

3.9

Version:

3.9

Interface Summary

Interface	Description
Op<T>	Operation interface.

Class Summary

Class	Description
Const<T>	Represents an operation which always returns the same, constant, value.
ConstRewriter<T>	This class rewrites constant expressions to its single value.
EphemeralConst<T>	Implementation of an ephemeral constant.
MathExpr	This class allows you to create a math operation tree from an expression string.
Program<T>	This class composes a given operation tree to a new operation.
Val<T>	This is the sealed base class for unmodifiable values.
Var<T>	Represents the program variables.

Enum Summary

Enum	Description
BoolOp	This class contains basic and secondary boolean operations.
MathOp	This class contains operations for performing basic numeric operations.