gololang

Class FunctionReference

java.lang.Object

gololang.FunctionReference

public class FunctionReference
extends java.lang.Object

A reference to a function / closure. This class essentially boxes MethodHandle references, and provides as many delegations as possible. Previous versions of Golo used direct MethodHandle objects to deal with functions by reference, but that class does not provide any mean to attach local state, as required for, say, implementing named arguments. This boxed representation provides a sound abstraction while not hurting performance, as org.eclipse.golo.runtime.ClosureCallSupport still dispatches through a method handle.

See Also:

MethodHandle, ClosureCallSupport

Constructor Summary

Constructors

Constructor and Description
FunctionReference(java.lang.invoke.MethodHandle handle) Makes a function reference from a method handle.
FunctionReference(java.lang.invoke.MethodHandle handle, java.lang.String[] parameterNames) Makes a function reference from a method handle.

Method Summary

Modifier and Type	Method and Description
boolean	acceptArity(int nb) Check if this function can be invoked with the given number of arguments.
FunctionReference	andThen(FunctionReference fun) Compose a function with another function.
int	arity() Returns the arity of the function.
FunctionReference	asCollector(java.lang.Class<?> arrayType, int arrayLength)
FunctionReference	asCollector(int arrayLength)
FunctionReference	asFixedArity()
FunctionReference	asSpreader()
FunctionReference	asSpreader(java.lang.Class<?> arrayType, int arrayLength)
FunctionReference	asSpreader(int arrayLength)
FunctionReference	asType(java.lang.invoke.MethodType newType)
FunctionReference	asVarargsCollector()
FunctionReference	asVarargsCollector(java.lang.Class<?> arrayType)
FunctionReference	bindAt(int position, java.lang.Object value) Partial application.
FunctionReference	bindAt(java.lang.String parameterName, java.lang.Object value) Partial application based on parameter's names.
FunctionReference	bindTo(java.lang.Object x)
FunctionReference	compose(FunctionReference fun)
boolean	equals(java.lang.Object obj)
java.lang.invoke.MethodHandle	handle() Unboxes the method handle.
int	hashCode()
FunctionReference	insertArguments(int position, java.lang.Object... values) Partial application.
java.lang.Object	invoke(java.lang.Object... args)
java.lang.Object	invokeOrBind(java.lang.Object... args) Apply the function to the provided arguments.
boolean	isVarargsCollector()
java.lang.String[]	parameterNames() Get the target function parameter's names
java.lang.Object	spread(java.lang.Object... arguments) Spread arguments over this function parameters.
java.lang.Object	to(java.lang.Class<?> interfaceClass) Converts a function reference to an instance of an interface.
java.lang.String	toString()
java.lang.invoke.MethodType	type()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

FunctionReference

public FunctionReference(java.lang.invoke.MethodHandle handle,
                         java.lang.String[] parameterNames)

Makes a function reference from a method handle.

Parameters:

handle - the method handle.

parameterNames - the target method parameter's names.

Throws:

java.lang.IllegalArgumentException - if handle is null.

FunctionReference

public FunctionReference(java.lang.invoke.MethodHandle handle)

Makes a function reference from a method handle. The parameter names will be null.

Parameters:

handle - the method handle.

Throws:

java.lang.IllegalArgumentException - if handle is null.

Method Detail

handle

public java.lang.invoke.MethodHandle handle()

Unboxes the method handle.

Returns:

the (boxed) method handle.

parameterNames

public java.lang.String[] parameterNames()

Get the target function parameter's names

Returns:

the array of parameter's names

type

public java.lang.invoke.MethodType type()

asCollector

public FunctionReference asCollector(java.lang.Class<?> arrayType,
                                     int arrayLength)

asCollector

public FunctionReference asCollector(int arrayLength)

asFixedArity

public FunctionReference asFixedArity()

asType

public FunctionReference asType(java.lang.invoke.MethodType newType)

asVarargsCollector

public FunctionReference asVarargsCollector(java.lang.Class<?> arrayType)

asVarargsCollector

public FunctionReference asVarargsCollector()

bindTo

public FunctionReference bindTo(java.lang.Object x)

isVarargsCollector

public boolean isVarargsCollector()

asSpreader

public FunctionReference asSpreader(java.lang.Class<?> arrayType,
                                    int arrayLength)

asSpreader

public FunctionReference asSpreader(int arrayLength)

asSpreader

public FunctionReference asSpreader()

arity

public int arity()

Returns the arity of the function. The arity is the number of declared parameter in the function signature.

Returns:

the number of declared parameter

acceptArity

public boolean acceptArity(int nb)

Check if this function can be invoked with the given number of arguments.

invoke

public java.lang.Object invoke(java.lang.Object... args)
                        throws java.lang.Throwable

Throws:

java.lang.Throwable

invokeOrBind

public java.lang.Object invokeOrBind(java.lang.Object... args)
                              throws java.lang.Throwable

Apply the function to the provided arguments. If the number of arguments corresponds to the function arity, the function is applied. Otherwise, a function partialized with the given arguments is returned.

Returns:

the result of the function or a partialized version of the function

Throws:

java.lang.Throwable

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

to

public java.lang.Object to(java.lang.Class<?> interfaceClass)

Converts a function reference to an instance of an interface.

Parameters:

interfaceClass - the interface,

Returns:

a proxy object that satisfies interfaceClass and delegates to this.

andThen

public FunctionReference andThen(FunctionReference fun)

Compose a function with another function. The fun function must accept 1 parameter that will be the value returned by this function, or no parameter, in which case the returned value will be ignored. The resulting function may throw a ClassCastException on invocation if the return type of this function does not match the type of the fun parameter.

Parameters:

fun - the function that processes the results of this function.

Returns:

a composed function.

compose

public FunctionReference compose(FunctionReference fun)

bindAt

public FunctionReference bindAt(int position,
                                java.lang.Object value)

Partial application.

Parameters:

position - the argument position (0-indexed).

value - the argument value.

Returns:

a partially applied function.

bindAt

public FunctionReference bindAt(java.lang.String parameterName,
                                java.lang.Object value)

Partial application based on parameter's names.

Parameters:

parameterName - the parameter to bind.

value - the argument value.

Returns:

a partially applied function.

insertArguments

public FunctionReference insertArguments(int position,
                                         java.lang.Object... values)

Partial application.

Parameters:

position - the first argument position.

values - the values of the arguments from position.

Returns:

a partially applied function.

See Also:

MethodHandles.insertArguments(MethodHandle, int, Object...)

spread

public java.lang.Object spread(java.lang.Object... arguments)
                        throws java.lang.Throwable

Spread arguments over this function parameters.

Parameters:

arguments - arguments as an array.

Returns:

a return value.

Throws:

java.lang.Throwable - ...because an exception can be thrown.