fj.function

Class Visitor

java.lang.Object

fj.function.Visitor

public final class Visitor
extends java.lang.Object

The essence of the visitor design pattern expressed polymorphically.

Method Summary

Modifier and Type	Method and Description
static <A,B> F<B,F<A,B>>	association(List<P2<A,B>> x, Equal<A> eq) Uses an association list to perform a lookup with equality and returns a function that can be applied to a default, followed by the associated key to return a value.
static <A,B> F<P1<B>,F<A,B>>	associationLazy(List<P2<A,B>> x, Equal<A> eq) Uses an association list to perform a lookup with equality and returns a function that can be applied to a default, followed by the associated key to return a value.
static <X> X	findFirst(List<Option<X>> values, F0<X> def) Returns the first value available in the given list of optional values.
static <X> X	nullablefindFirst(List<X> values, F0<X> def) Returns the first non-null value in the given list of optional values.
static <A,B> B	nullableVisitor(List<F<A,B>> visitors, F0<B> def, A value) Returns the first non-null value found in the list of visitors after application of the given value, otherwise returns the given default.
static <A,B> B	visitor(List<F<A,Option<B>>> visitors, F0<B> def, A value) Returns the first value found in the list of visitors after application of the given value, otherwise returns the given default.

Methods inherited from class java.lang.Object

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

Method Detail

findFirst

public static <X> X findFirst(List<Option<X>> values,
                              F0<X> def)

Returns the first value available in the given list of optional values. If none is found return the given default value.

Parameters:

values - The optional values to search.

def - The default value if no value is found in the list.

Returns:

The first value available in the given list of optional values. If none is found return the given default value.

nullablefindFirst

public static <X> X nullablefindFirst(List<X> values,
                                      F0<X> def)

Returns the first non-null value in the given list of optional values. If none is found return the given default value.

Parameters:

values - The potentially null values to search.

def - The default value if no value is found in the list.

Returns:

The first non-null value in the given list of optional values. If none is found return the given default value.

visitor

public static <A,B> B visitor(List<F<A,Option<B>>> visitors,
                              F0<B> def,
                              A value)

Returns the first value found in the list of visitors after application of the given value, otherwise returns the given default.

Parameters:

visitors - The list of visitors to apply.

def - The default if none of the visitors yield a value.

value - The value to apply to the visitors.

Returns:

The first value found in the list of visitors after application of the given value, otherwise returns the given default.

nullableVisitor

public static <A,B> B nullableVisitor(List<F<A,B>> visitors,
                                      F0<B> def,
                                      A value)

Returns the first non-null value found in the list of visitors after application of the given value, otherwise returns the given default.

Parameters:

visitors - The list of visitors to apply looking for a non-null.

def - The default if none of the visitors yield a non-null value.

value - The value to apply to the visitors.

Returns:

The first value found in the list of visitors after application of the given value, otherwise returns the given default.

association

public static <A,B> F<B,F<A,B>> association(List<P2<A,B>> x,
                                            Equal<A> eq)

Uses an association list to perform a lookup with equality and returns a function that can be applied to a default, followed by the associated key to return a value.

Parameters:

x - The association list.

eq - The equality for the association list keys.

Returns:

A function that can be applied to a default value (there is no association) and an associated key.

associationLazy

public static <A,B> F<P1<B>,F<A,B>> associationLazy(List<P2<A,B>> x,
                                                    Equal<A> eq)

Uses an association list to perform a lookup with equality and returns a function that can be applied to a default, followed by the associated key to return a value.

Parameters:

x - The association list.

eq - The equality for the association list keys.

Returns:

A function that can be applied to a default value (there is no association) and an associated key.