net.sf.eos.util
Class Compositions

java.lang.Object
  net.sf.eos.util.Compositions

@Experimental
public class Compositions
extends Object

Defines some useful compositions for handling with Functions, Predicates and Suppliers.

Each composition follows the rule of a from or source entity, propagating its result value to a to or target entity.

Author:

Sascha Kohlmann

Method Summary

static <F,I,T> Function<F,T>	compose(Function<? super F,? extends I> from, Function<? super I,? extends T> to) Returns the composition of two functions.
static <F,T> Predicate<F>	compose(Function<? super F,? extends T> fromFunction, Predicate<T> toPredicate) Returns a composition of a from Function and an evaluating to Predicate.
static <F,T> Supplier<T>	compose(Supplier<? extends F> fromSupplier, Function<F,T> toFunction) Returns a composition of a from Supplier and an applied to Function.
static <F,T> Function<F,T>	composeRule(Predicate<? super F> decider, Function<? super F,? extends T> trueFunction, Function<? super F,? extends T> falseFunction) Composes a rule.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

compose

public static final <F,I,T> Function<F,T> compose(Function<? super F,? extends I> from,
                                                  Function<? super I,? extends T> to)

Returns the composition of two functions. For f: F→I and g: I→T, composition is defined as the function h such that h(x) == g(f(x)) for each x.

The usage interface is designed as a from function which propagates its result to the to function.

Type Parameters:

F - the from or source type

I - the intermediate type

T - the to or target type

Parameters:

from - the from or source function

to - the to or target function

Throws:

IllegalArgumentException - if one parameter is null

Since:

0.1.0

compose

public static final <F,T> Predicate<F> compose(Function<? super F,? extends T> fromFunction,
                                               Predicate<T> toPredicate)

Returns a composition of a from Function and an evaluating to Predicate. The predicate retrieves the value from the function.

The usage interface is designed as a from function which propagates its result to the to predicate.

Type Parameters:

F - the from or source type

T - the to or target type

Parameters:

fromFunction - the from or source function

toPredicate - the to or target predicate

Returns:

a predicate

Throws:

IllegalArgumentException - if one parameter is null

Since:

0.7.0

compose

public static final <F,T> Supplier<T> compose(Supplier<? extends F> fromSupplier,
                                              Function<F,T> toFunction)

Returns a composition of a from Supplier and an applied to Function. The function retrieves the value from the supplier.

The usage interface is designed as a from supplier which propagates its result to the to function.

Type Parameters:

F - the from or source type

T - the to or target type

Parameters:

fromSupplier - the from or source supplier

toFunction - the to or target function

Returns:

a supplier with the value from function

Throws:

IllegalArgumentException - if one parameter is null

Since:

0.7.0

composeRule

public static final <F,T> Function<F,T> composeRule(Predicate<? super F> decider,
                                                    Function<? super F,? extends T> trueFunction,
                                                    Function<? super F,? extends T> falseFunction)

Composes a rule. A rule contains a predicate as decision maker either to call the trueFunction or the falseFunction. The returning function calls the trueFunction if predicate returns true. Otherwise the falseFunction will call.

Type Parameters:

F - the input type of the predicate and the functions

T - the output type of the applyied functions

Parameters:

decider - the decision maker

trueFunction - apply if the decision maker returns true

falseFunction - apply if the decision maker returns false

Returns:

a ruling function

Since:

0.8.1