org.opencastproject.util.data.functions

Class Functions

java.lang.Object

org.opencastproject.util.data.functions.Functions

public final class Functions
extends Object

General purpose functions, especially function transformations.

Field Summary

Fields

Modifier and Type	Field and Description
static Effect0	noop Noop effect.
static Effect<Effect0>	run Create an effect that runs its argument.

Method Summary

Modifier and Type	Method and Description
static <A> Effect<A>	all(Effect<? super A>... es) Create an effect that runs all given effects in order.
static Effect0	all(Effect0... es) Create an effect that runs all given effects in order.
static <A,B> Function<List<A>,List<B>>	bind(Function<A,List<B>> f) Create a bound version of f for List.
static <A,B> Function<Option<A>,Option<B>>	bindOpt(Function<A,Option<B>> f) Create a bound version of f for Option.
static <A> A	chuck(Throwable t) Throw a checked exception like a RuntimeException removing any needs to declare a throws clause.
static <A,B> Function<Function<A,? extends B>,Function<A,B>>	co()
static <A,B> Function<A,B>	co(Function<? super A,? extends B> f) Pure functions are covariant in their result type.
static <A> Function<A,A>	concat(Function<? super A,? extends A>... fs) Multiple `then` concatenation.
static <A,B> Function<A,B>	constant(B b) Constant function that always returns b.
static <A> Function0<A>	constant0(A a) Constant function that always returns a.
static <A,B> Function<A,B>	contra(Function<? super A,B> f) Pure functions are contravariant in their argument type.
static <A,B> Function0<B>	curry(Function<? super A,? extends B> f, A a) Curry a function of arity 1.
static <A,B> Function<A,Function0<B>>	curry(Function<A,B> f) Curry a function of arity 1.
static <A,B,C> Function<A,Function<B,C>>	curry(Function2<? super A,? super B,? extends C> f) Curry a function of arity 2.
static <A,B,C> Function<B,C>	curry(Function2<? super A,? super B,? extends C> f, A a) Curry a function of arity 2.
static <A,B,C> Function<A,Either<C,B>>	either(Function<? super A,? extends B> f, Function<? super Exception,? extends C> handler) Create a new function from f decorated with an exception handler.
static <A,B,C> Function2<B,A,C>	flip(Function2<? super A,? super B,? extends C> f) Flip arguments of a function of arity 2.
static <A,B> com.entwinemedia.fn.Fn<A,B>	fn(Function<A,B> f) Create a function from the matterhorn-fn module from a common function.
static <A,B> Function<A,B>	handle(Function<? super A,? extends B> f, Function<? super Exception,? extends B> handler) Create a new function from f decorated with an exception handler.
static <A> Function<A,A>	identity() Identity function.
static <A> Function<A,A>	identity(A example) Identity function.
static <A> Function<A,A>	identity(Class<A> clazz) Identity function.
static <A,B> Function<A,B>	ignore(B b) Constant function that ignores its argument and always returns a.
static <A,B,C> Function<A,List<C>>	kleisliCompList(Function<? super A,List<B>> m, Function<? super B,List<C>> n) Kleisli composition of list monads.
static <A,B> Function<List<A>,List<B>>	liftList(Function<A,B> f) Promote function a -> b to a List.
static <A> Function<Option<A>,Option<A>>	liftOpt(Effect<? super A> f) Promote effect a -> () to an Option.
static <A,B> Function<Option<A>,Option<B>>	liftOpt(Function<? super A,? extends B> f) Promote function a -> b to an Option.
static <A> Effect<A>	noop() Noop effect.
static <A,B> Function0<B>	o(Function<? super A,? extends B> f, Function0<? extends A> g) Function composition: f .
static <A,B,C> Function<A,C>	o(Function<? super B,? extends C> f, Function<? super A,? extends B> g) Function composition: f .
static <A,B,C,D> Function<A,D>	o(Function<? super C,? extends D> f, Function<? super B,? extends C> g, Function<? super A,? extends B> h) f .
static <A,B,C,D,E> Function<A,E>	o(Function<? super D,? extends E> f, Function<? super C,? extends D> g, Function<? super B,? extends C> h, Function<? super A,? extends B> i) f .
static <A,B> Function<A,B>	orElse(B zero, Function<? super A,Option<B>>... fs) Treat fs as partial functions.
static <A,B> Function<A,B>	rethrow(Function<? super A,? extends B> f, Function<? super Exception,? extends Exception> transformer) Create a new function from f decorated with an exception transformer.
static <A> Effect<Effect<A>>	run(A a) Create an effect that runs its argument passing in a.
static <A,B,C> Function<A,C>	then(Function<? super A,? extends B> f, Function<? super B,? extends C> g) Left to right composition: f then g = g(f(x))
static <A,B> Function0<B>	then(Function0<? extends A> f, Function<? super A,? extends B> g) Left to right composition: f then g = g(f)
static <A,B> Function0<B>	then(Function0<? extends A> f, Function0<? extends B> g) Apply f and ignore its result, then apply g.
static <A,B> Effect<A>	toEffect(Function<? super A,? extends B> f) Turn a function into an effect by discarding its result.
static <A> Effect0	toEffect(Function0<A> f) Turn a function of arity 0 into an effect by discarding its result.
static <A,B,C> Effect2<A,B>	toEffect(Function2<? super A,? super B,? extends C> f) Turn a function of arity 2 into an effect by discarding its result.
static <A,B> Function<A,Option<B>>	toFn(Map<? extends A,? extends B> m) Create a (partial) function from a map.
static <A,B> com.google.common.base.Function<A,B>	toGuava(Function<? super A,? extends B> f) Convert function f into a guava function.
static <A> Predicate<A>	toPredicate(Function<? super A,Boolean> f)
static <A,B,C> Function<Tuple<A,B>,C>	tupled(Function2<? super A,? super B,? extends C> f) Create a tupled version of a function of arity 2.
static <A,B,C> Function2<A,B,C>	uncurry(Function<? super A,Function<B,C>> f) Uncurry to a function of arity 2.
static <A,B> Function<A,B>	variant(Function<? super A,? extends B> f) Pure functions are covariant in their result type and contravariant in their argument type.

Methods inherited from class java.lang.Object

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

Field Detail

noop

public static final Effect0 noop

Noop effect.

run

public static final Effect<Effect0> run

Create an effect that runs its argument.

Method Detail

fn

public static <A,B> com.entwinemedia.fn.Fn<A,B> fn(Function<A,B> f)

Create a function from the matterhorn-fn module from a common function.

o

public static <A,B,C> Function<A,C> o(Function<? super B,? extends C> f,
                                      Function<? super A,? extends B> g)

Function composition: f . g = f(g(x)) = o(f, g)

o

public static <A,B> Function0<B> o(Function<? super A,? extends B> f,
                                   Function0<? extends A> g)

Function composition: f . g = f(g) = o(f, g)

o

public static <A,B,C,D> Function<A,D> o(Function<? super C,? extends D> f,
                                        Function<? super B,? extends C> g,
                                        Function<? super A,? extends B> h)

f . g . h

o

public static <A,B,C,D,E> Function<A,E> o(Function<? super D,? extends E> f,
                                          Function<? super C,? extends D> g,
                                          Function<? super B,? extends C> h,
                                          Function<? super A,? extends B> i)

f . g . h . i

concat

public static <A> Function<A,A> concat(Function<? super A,? extends A>... fs)

Multiple `then` concatenation. f1 then f2 then ... fn

then

public static <A,B,C> Function<A,C> then(Function<? super A,? extends B> f,
                                         Function<? super B,? extends C> g)

Left to right composition: f then g = g(f(x))

then

public static <A,B> Function0<B> then(Function0<? extends A> f,
                                      Function<? super A,? extends B> g)

Left to right composition: f then g = g(f)

then

public static <A,B> Function0<B> then(Function0<? extends A> f,
                                      Function0<? extends B> g)

Apply f and ignore its result, then apply g.

rethrow

public static <A,B> Function<A,B> rethrow(Function<? super A,? extends B> f,
                                          Function<? super Exception,? extends Exception> transformer)

Create a new function from f decorated with an exception transformer. Any exception that occurs during application of f is passed to transformer whose return value is then being thrown.

handle

public static <A,B> Function<A,B> handle(Function<? super A,? extends B> f,
                                         Function<? super Exception,? extends B> handler)

Create a new function from f decorated with an exception handler. Any exception that occurs during application of f is passed to handler whose return value is then being returned.

either

public static <A,B,C> Function<A,Either<C,B>> either(Function<? super A,? extends B> f,
                                                     Function<? super Exception,? extends C> handler)

Create a new function from f decorated with an exception handler. The new function either returns the value of f or in case of an exception being thrown on the application of f the return value of handler.

curry

public static <A,B,C> Function<B,C> curry(Function2<? super A,? super B,? extends C> f,
                                          A a)

Curry a function of arity 2.

curry

public static <A,B,C> Function<A,Function<B,C>> curry(Function2<? super A,? super B,? extends C> f)

Curry a function of arity 2. (a, b) -gt; c =gt; a -gt; b -gt; c

uncurry

public static <A,B,C> Function2<A,B,C> uncurry(Function<? super A,Function<B,C>> f)

Uncurry to a function of arity 2. a -gt; b -gt; c =gt; (a, b) -gt; c

curry

public static <A,B> Function0<B> curry(Function<? super A,? extends B> f,
                                       A a)

Curry a function of arity 1.

curry

public static <A,B> Function<A,Function0<B>> curry(Function<A,B> f)

Curry a function of arity 1.

tupled

public static <A,B,C> Function<Tuple<A,B>,C> tupled(Function2<? super A,? super B,? extends C> f)

Create a tupled version of a function of arity 2.

flip

public static <A,B,C> Function2<B,A,C> flip(Function2<? super A,? super B,? extends C> f)

Flip arguments of a function of arity 2.

toEffect

public static <A> Effect0 toEffect(Function0<A> f)

Turn a function of arity 0 into an effect by discarding its result.

toEffect

public static <A,B> Effect<A> toEffect(Function<? super A,? extends B> f)

Turn a function into an effect by discarding its result.

toEffect

public static <A,B,C> Effect2<A,B> toEffect(Function2<? super A,? super B,? extends C> f)

Turn a function of arity 2 into an effect by discarding its result.

toPredicate

public static <A> Predicate<A> toPredicate(Function<? super A,Boolean> f)

noop

public static <A> Effect<A> noop()

Noop effect.

identity

public static <A> Function<A,A> identity()

Identity function.

identity

public static <A> Function<A,A> identity(A example)

Identity function. The type is based on the type of the example object to save some nasty typing, e.g. Function.<Integer>identity() vs. identity(0) Please note that this constructor is only due to Java's insufficient type inference.

identity

public static <A> Function<A,A> identity(Class<A> clazz)

Identity function.

Parameters:

clazz - to describe the functions's type

constant0

public static <A> Function0<A> constant0(A a)

Constant function that always returns a.

constant

public static <A,B> Function<A,B> constant(B b)

Constant function that always returns b.

ignore

public static <A,B> Function<A,B> ignore(B b)

Constant function that ignores its argument and always returns a.

liftOpt

public static <A,B> Function<Option<A>,Option<B>> liftOpt(Function<? super A,? extends B> f)

Promote function a -> b to an Option.

liftOpt

public static <A> Function<Option<A>,Option<A>> liftOpt(Effect<? super A> f)

Promote effect a -> () to an Option.

bindOpt

public static <A,B> Function<Option<A>,Option<B>> bindOpt(Function<A,Option<B>> f)

Create a bound version of f for Option.

liftList

public static <A,B> Function<List<A>,List<B>> liftList(Function<A,B> f)

Promote function a -> b to a List.

bind

public static <A,B> Function<List<A>,List<B>> bind(Function<A,List<B>> f)

Create a bound version of f for List.

run

public static <A> Effect<Effect<A>> run(A a)

Create an effect that runs its argument passing in a.

all

public static Effect0 all(Effect0... es)

Create an effect that runs all given effects in order.

all

public static <A> Effect<A> all(Effect<? super A>... es)

Create an effect that runs all given effects in order.

co

public static <A,B> Function<A,B> co(Function<? super A,? extends B> f)

Pure functions are covariant in their result type.

co

public static <A,B> Function<Function<A,? extends B>,Function<A,B>> co()

contra

public static <A,B> Function<A,B> contra(Function<? super A,B> f)

Pure functions are contravariant in their argument type.

variant

public static <A,B> Function<A,B> variant(Function<? super A,? extends B> f)

Pure functions are covariant in their result type and contravariant in their argument type.

chuck

public static <A> A chuck(Throwable t)

Throw a checked exception like a RuntimeException removing any needs to declare a throws clause. This technique has been described by James Iry at http://james-iry.blogspot.de/2010/08/on-removing-java-checked-exceptions-by.html

kleisliCompList

public static <A,B,C> Function<A,List<C>> kleisliCompList(Function<? super A,List<B>> m,
                                                          Function<? super B,List<C>> n)

Kleisli composition of list monads. (a -> m b) -> (b -> m c) -> a -> m c

toGuava

public static <A,B> com.google.common.base.Function<A,B> toGuava(Function<? super A,? extends B> f)

Convert function f into a guava function.

toFn

public static <A,B> Function<A,Option<B>> toFn(Map<? extends A,? extends B> m)

Create a (partial) function from a map.

orElse

public static <A,B> Function<A,B> orElse(B zero,
                                         Function<? super A,Option<B>>... fs)

Treat fs as partial functions. Apply the argument a of the returned function to the functions fs in order unless some value is returned. Return zero if none of the functions is defined at a.