Package com.ontology2.pidove.util

Class Composer

java.lang.Object

com.ontology2.pidove.util.Composer

public class Composer
extends Object

Many programming languages have a function for composing functions; here is an attempt to make the most of the concept in Java. One limitation here is that to take advantage of the strong typing in Java we have to generate a large number of functions with different signatures. The ideal grammar of compose is that the first argument is a Supplier, Function, or BiFunction. In the middle there could be an arbitrary number of functions, at the end there either a Function, Consumer, or Predicate. That gives 9 basic forms, and these could be extended to some length N of intervening functions. A challenge with this idea is that a lambda function like x -> -x can be alternately be treated as a Consumer or a Function and one like x -> x == 15 can be treated as as either a Function or a Predicate so for this to work we have to change the name of the function. To support, say N=10 this is a job for code generation.

Constructor Summary

Constructors

Constructor	Description
Composer()

Method Summary

Modifier and Type	Method	Description
static <A, B, X, C> BiFunction<A,B,C>	compose(BiFunction<A,B,X> f1, Function<X,C> f2)
static <A, B, X> Function<A,B>	compose(Function<A,X> f1, Function<X,B> f2)
static <A, B, X1, X2> Function<A,B>	compose(Function<A,X1> f1, Function<X1,X2> f2, Function<X2,B> f3)
static <A, B, X1, X2, X3> Function<A,B>	compose(Function<A,X1> f1, Function<X1,X2> f2, Function<X2,X3> f3, Function<X3,B> f4)
static <A, B> Supplier<B>	compose(Supplier<A> f1, Function<A,B> f2)
static <A, B, X> BiPredicate<A,B>	composePredicate(BiFunction<A,B,X> f1, Predicate<X> f2)
static <A, B> Predicate<A>	composePredicate(Function<A,B> f1, Predicate<B> f2)	Function<X,Boolean> is ambiguous with Predicate<X> so we need to change the name of this function so it doesn't conflict with ordinary compose.
static <A, B> Consumer<A>	composeVoid(Function<A,B> f1, Consumer<B> f2)

Methods inherited from class java.lang.Object

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

Constructor Details

Composer

public Composer()

Method Details

compose

public static <A,
B,
X> Function<A,B> compose(Function<A,X> f1,
 Function<X,B> f2)

compose

public static <A,
B,
X1,
X2> Function<A,B> compose(Function<A,X1> f1,
 Function<X1,X2> f2,
 Function<X2,B> f3)

compose

public static <A,
B,
X1,
X2,
X3> Function<A,B> compose(Function<A,X1> f1,
 Function<X1,X2> f2,
 Function<X2,X3> f3,
 Function<X3,B> f4)

compose

public static <A,
B> Supplier<B> compose(Supplier<A> f1,
 Function<A,B> f2)

composeVoid

public static <A,
B> Consumer<A> composeVoid(Function<A,B> f1,
 Consumer<B> f2)

compose

public static <A,
B,
X,
C> BiFunction<A,B,C> compose(BiFunction<A,B,X> f1,
 Function<X,C> f2)

composePredicate

public static <A,
B> Predicate<A> composePredicate(Function<A,B> f1,
 Predicate<B> f2)

Function<X,Boolean> is ambiguous with Predicate<X> so we need to change the name of this function so it doesn't conflict with ordinary compose.

Type Parameters:

A - input type

B - inner type of predicate

Parameters:

f1 - first function

f2 - second function, a predicate

Returns:

true or false depending on predicate

composePredicate

public static <A,
B,
X> BiPredicate<A,B> composePredicate(BiFunction<A,B,X> f1,
 Predicate<X> f2)