Function0 (vavr 1.0.0-alpha-4 API)

Type Parameters:

R - return type of the function

All Superinterfaces:

java.io.Serializable, java.util.function.Supplier<R>

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
```
@FunctionalInterface
public interface Function0<R>
extends java.io.Serializable, java.util.function.Supplier<R>
```
Represents a function with no arguments.

Field Summary

Fields
Modifier and Type Field and Description

static long serialVersionUID
The serial version uid.

Fields
Modifier and Type	Field and Description
`static long`	`serialVersionUID` The serial version uid.

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method and Description
`default <V> Function0<V>`	`andThen(java.util.function.Function<? super R,? extends V> after)` Returns a composed function that first applies this Function0 to the given argument and then applies Function `after` to the result.
`R`	`apply()` Applies this function to no arguments and returns the result.
`default int`	`arity()` Returns the number of function arguments.
`static <R> Function0<R>`	`constant(R value)` Returns a function that always returns the constant value that you give in parameter.
`default Function0<R>`	`curried()` Returns a curried version of this function.
`default R`	`get()` Implementation of Supplier.get(), just calls apply().
`default boolean`	`isMemoized()` Checks if this function is memoizing (= caching) computed values.
`static <R> Function0<Option<R>>`	`lift(java.util.function.Supplier<? extends R> partialFunction)` Lifts the given `partialFunction` into a total function that returns an `Option` result.
`static <R> Function0<Try<R>>`	`liftTry(java.util.function.Supplier<? extends R> partialFunction)` Lifts the given `partialFunction` into a total function that returns an `Try` result.
`default Function0<R>`	`memoized()` Returns a memoizing version of this function, which computes the return value for given arguments only one time.
`static <R> Function0<R>`	`narrow(Function0<? extends R> f)` Narrows the given `Function0<? extends R>` to `Function0<R>`
`static <R> Function0<R>`	`of(Function0<R> methodReference)` Creates a `Function0` based on method reference lambda expression Examples (w.l.o.g.
`default Function0<R>`	`reversed()` Returns a reversed version of this function.
`default Function1<Tuple0,R>`	`tupled()` Returns a tupled version of this function.

- Field Detail
  - serialVersionUID
```
static final long serialVersionUID
```
    The serial version uid.
    
    See Also:
    
    Constant Field Values
- Method Detail
  - constant
```
static <R> Function0<R> constant(R value)
```
    Returns a function that always returns the constant value that you give in parameter.
    
    Type Parameters:
    
    R - the result type
    
    Parameters:
    
    value - the value to be returned
    
    Returns:
    
    a function always returning the given value
  - of
```
static <R> Function0<R> of(Function0<R> methodReference)
```
    Creates a Function0 based on
    - method reference
    - lambda expression
    Examples (w.l.o.g. referring to Function1):
```
// using a lambda expression
 Function1<Integer, Integer> add1 = Function1.of(i -> i + 1);

 // using a method reference (, e.g. Integer method(Integer i) { return i + 1; })
 Function1<Integer, Integer> add2 = Function1.of(this::method);

 // using a lambda reference
 Function1<Integer, Integer> add3 = Function1.of(add1::apply);
 
```
    Caution: Reflection loses type information of lambda references.
```
// type of a lambda expression
 Type<?, ?> type1 = add1.getType(); // (Integer) -> Integer

 // type of a method reference
 Type<?, ?> type2 = add2.getType(); // (Integer) -> Integer

 // type of a lambda reference
 Type<?, ?> type3 = add3.getType(); // (Object) -> Object
 
```
    Type Parameters:
    
    R - return type
    
    Parameters:
    
    methodReference - (typically) a method reference, e.g. Type::method
    
    Returns:
    
    a Function0
  - lift
```
static <R> Function0<Option<R>> lift(java.util.function.Supplier<? extends R> partialFunction)
```
    Lifts the given partialFunction into a total function that returns an Option result.
    
    Type Parameters:
    
    R - return type
    
    Parameters:
    
    partialFunction - a function that is not defined for all values of the domain (e.g. by throwing)
    
    Returns:
    
    a function that applies arguments to the given partialFunction and returns Some(result) if the function is defined for the given arguments, and None otherwise.
  - liftTry
```
static <R> Function0<Try<R>> liftTry(java.util.function.Supplier<? extends R> partialFunction)
```
    Lifts the given partialFunction into a total function that returns an Try result.
    
    Type Parameters:
    
    R - return type
    
    Parameters:
    
    partialFunction - a function that is not defined for all values of the domain (e.g. by throwing)
    
    Returns:
    
    a function that applies arguments to the given partialFunction and returns Success(result) if the function is defined for the given arguments, and Failure(throwable) otherwise.
  - narrow
```
static <R> Function0<R> narrow(Function0<? extends R> f)
```
    Narrows the given Function0<? extends R> to Function0<R>
    
    Type Parameters:
    
    R - return type
    
    Parameters:
    
    f - A Function0
    
    Returns:
    
    the given f instance as narrowed type Function0<R>
  - apply
```
R apply()
```
    Applies this function to no arguments and returns the result.
    
    Returns:
    
    the result of function application
  - get
```
default R get()
```
    Implementation of Supplier.get(), just calls apply().
    
    Specified by:
    
    get in interface java.util.function.Supplier<R>
    
    Returns:
    
    the result of apply()
  - arity
```
default int arity()
```
    Returns the number of function arguments.
    
    Returns:
    
    an int value >= 0
    
    See Also:
    
    Arity
  - curried
```
default Function0<R> curried()
```
    Returns a curried version of this function.
    
    Returns:
    
    a curried function equivalent to this.
  - tupled
```
default Function1<Tuple0,R> tupled()
```
    Returns a tupled version of this function.
    
    Returns:
    
    a tupled function equivalent to this.
  - reversed
```
default Function0<R> reversed()
```
    Returns a reversed version of this function. This may be useful in a recursive context.
    
    Returns:
    
    a reversed function equivalent to this.
  - memoized
```
default Function0<R> memoized()
```
    Returns a memoizing version of this function, which computes the return value for given arguments only one time. On subsequent calls given the same arguments the memoized value is returned.
    Please note that memoizing functions do not permit null as single argument or return value.
    
    Returns:
    
    a memoizing function equivalent to this.
  - isMemoized
```
default boolean isMemoized()
```
    Checks if this function is memoizing (= caching) computed values.
    
    Returns:
    
    true, if this function is memoizing, false otherwise
  - andThen
```
default <V> Function0<V> andThen(java.util.function.Function<? super R,? extends V> after)
```
    Returns a composed function that first applies this Function0 to the given argument and then applies Function after to the result.
    
    Type Parameters:
    
    V - return type of after
    
    Parameters:
    
    after - the function applied after this
    
    Returns:
    
    a function composed of this and after
    
    Throws:
    
    java.lang.NullPointerException - if after is null

Interface Function0<R>

Field Summary

Method Summary

Field Detail

serialVersionUID

Method Detail

constant

of

lift

liftTry

narrow

apply

get

arity

curried

tupled

reversed

memoized

isMemoized

andThen