fj.data

Class Enumerator<A>

java.lang.Object

fj.data.Enumerator<A>

public final class Enumerator<A>
extends java.lang.Object

Abstracts over a type that may have a successor and/or predecessor value. This implies ordering for that type. A user may construct an enumerator with an optimised version for plus, otherwise a default is implemented using the given successor/predecessor implementations.

For any enumerator e, the following laws must satisfy:

• forall a. e.successor(a).forall(\t -> e.predecessor(t).forall(\z -> z == a))
• forall a. e.predecessor(a).forall(\t -> e.successor(t).forall(\z -> z == a))
• e.max().forall(\t -> e.successor(t).isNone)
• e.min().forall(\t -> e.predecessor(t).isNone)
• forall a n. e.plus(a, 0) == Some(a)
• forall a n | n > 0. e.plus(a, n) == e.plus(a, n - 1)
• forall a n | n < 0. e.plus(a, n) == e.plus(a, n + 1)

Field Summary

Fields

Modifier and Type	Field and Description
static Enumerator<java.math.BigDecimal>	bigdecimalEnumerator An enumerator for BigDecimal.
static Enumerator<java.math.BigInteger>	bigintEnumerator An enumerator for BigInteger.
static Enumerator<java.lang.Boolean>	booleanEnumerator An enumerator for boolean.
static Enumerator<java.lang.Byte>	byteEnumerator An enumerator for byte.
static Enumerator<java.lang.Character>	charEnumerator An enumerator for char.
static Enumerator<java.lang.Double>	doubleEnumerator An enumerator for double.
static Enumerator<java.lang.Float>	floatEnumerator An enumerator for float.
static Enumerator<java.lang.Integer>	intEnumerator An enumerator for int.
static Enumerator<java.lang.Long>	longEnumerator An enumerator for long.
static Enumerator<Natural>	naturalEnumerator An enumerator for Natural
static Enumerator<Ordering>	orderingEnumerator An enumerator for Ordering.
static Enumerator<java.lang.Short>	shortEnumerator An enumerator for short.

Method Summary

Modifier and Type	Method and Description
static <A> Enumerator<A>	enumerator(F<A,Option<A>> successor, F<A,Option<A>> predecessor, Option<A> max, Option<A> min, Ord<A> order) Construct an enumerator.
static <A> Enumerator<A>	enumerator(F<A,Option<A>> successor, F<A,Option<A>> predecessor, Option<A> max, Option<A> min, Ord<A> order, F<A,F<java.lang.Long,Option<A>>> plus) Construct an enumerator.
Option<A>	max() Returns the maximum value for this enumerator if there is one.
Option<A>	min() Returns the minimum value for this enumerator if there is one.
Ord<A>	order() Returns the ordering for the enumerator.
F<A,F<java.lang.Long,Option<A>>>	plus() Returns a function that moves a value along the enumerator a given number of times.
F<java.lang.Long,Option<A>>	plus(A a) Returns a function that moves a value along the enumerator a given number of times.
Option<A>	plus(A a, long l) Moves a value along the enumerator a given number of times.
F<A,Option<A>>	plus(long l) Returns a function that moves a value along the enumerator a given number of times.
F<A,Option<A>>	predecessor() Returns the potential predecessor of a value for this enumerator in curried form.
Option<A>	predecessor(A a) Returns the potential predecessor of a value for this enumerator.
Enumerator<A>	setMax(Option<A> max) Create a new enumerator with the given maximum value.
Enumerator<A>	setMin(Option<A> min) Create a new enumerator with the given minimum value.
F<A,Option<A>>	successor() Returns the potential successor of a value for this enumerator in curried form.
Option<A>	successor(A a) Returns the potential successor of a value for this enumerator.
Stream<A>	toStream(A a) Returns a stream of the values from this enumerator, starting at the given value, counting up.
<B> Enumerator<B>	xmap(F<A,B> f, F<B,A> g) Invariant functor map over this enumerator.

Methods inherited from class java.lang.Object

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

Field Detail

booleanEnumerator

public static final Enumerator<java.lang.Boolean> booleanEnumerator

An enumerator for boolean.

byteEnumerator

public static final Enumerator<java.lang.Byte> byteEnumerator

An enumerator for byte.

charEnumerator

public static final Enumerator<java.lang.Character> charEnumerator

An enumerator for char.

doubleEnumerator

public static final Enumerator<java.lang.Double> doubleEnumerator

An enumerator for double.

floatEnumerator

public static final Enumerator<java.lang.Float> floatEnumerator

An enumerator for float.

intEnumerator

public static final Enumerator<java.lang.Integer> intEnumerator

An enumerator for int.

bigintEnumerator

public static final Enumerator<java.math.BigInteger> bigintEnumerator

An enumerator for BigInteger.

bigdecimalEnumerator

public static final Enumerator<java.math.BigDecimal> bigdecimalEnumerator

An enumerator for BigDecimal.

longEnumerator

public static final Enumerator<java.lang.Long> longEnumerator

An enumerator for long.

shortEnumerator

public static final Enumerator<java.lang.Short> shortEnumerator

An enumerator for short.

orderingEnumerator

public static final Enumerator<Ordering> orderingEnumerator

An enumerator for Ordering.

naturalEnumerator

public static final Enumerator<Natural> naturalEnumerator

An enumerator for Natural

Method Detail

successor

public F<A,Option<A>> successor()

Returns the potential successor of a value for this enumerator in curried form.

Returns:

The potential successor of a value for this enumerator in curried form.

successor

public Option<A> successor(A a)

Returns the potential successor of a value for this enumerator.

Parameters:

a - The value to return the successor of.

Returns:

The potential successor of a value for this enumerator.

predecessor

public F<A,Option<A>> predecessor()

Returns the potential predecessor of a value for this enumerator in curried form.

Returns:

The potential predecessor of a value for this enumerator in curried form.

predecessor

public Option<A> predecessor(A a)

Returns the potential predecessor of a value for this enumerator.

Parameters:

a - The value to return the predecessor of.

Returns:

The potential predecessor of a value for this enumerator.

max

public Option<A> max()

Returns the maximum value for this enumerator if there is one.

Returns:

The maximum value for this enumerator if there is one.

min

public Option<A> min()

Returns the minimum value for this enumerator if there is one.

Returns:

The minimum value for this enumerator if there is one.

plus

public F<A,F<java.lang.Long,Option<A>>> plus()

Returns a function that moves a value along the enumerator a given number of times.

Returns:

A function that moves a value along the enumerator a given number of times.

plus

public F<java.lang.Long,Option<A>> plus(A a)

Returns a function that moves a value along the enumerator a given number of times.

Parameters:

a - The value to begin moving along from.

Returns:

A function that moves a value along the enumerator a given number of times.

plus

public F<A,Option<A>> plus(long l)

Returns a function that moves a value along the enumerator a given number of times.

Parameters:

l - The number of times to move along the enumerator.

Returns:

A function that moves a value along the enumerator a given number of times.

plus

public Option<A> plus(A a,
                      long l)

Moves a value along the enumerator a given number of times.

Parameters:

a - The value to begin moving along from.

l - The number of times to move along the enumerator.

Returns:

A potential value after having moved the given number of times.

order

public Ord<A> order()

Returns the ordering for the enumerator.

Returns:

The ordering for the enumerator.

xmap

public <B> Enumerator<B> xmap(F<A,B> f,
                              F<B,A> g)

Invariant functor map over this enumerator.

Parameters:

f - The covariant map.

g - The contra-variant map.

Returns:

An enumerator after the given functions are applied.

toStream

public Stream<A> toStream(A a)

Returns a stream of the values from this enumerator, starting at the given value, counting up.

Parameters:

a - A value at which to begin the stream.

Returns:

a stream of the values from this enumerator, starting at the given value, counting up.

setMin

public Enumerator<A> setMin(Option<A> min)

Create a new enumerator with the given minimum value.

Parameters:

min - A minimum value.

Returns:

A new enumerator identical to this one, but with the given minimum value.

setMax

public Enumerator<A> setMax(Option<A> max)

Create a new enumerator with the given maximum value.

Parameters:

max - A maximum value.

Returns:

A new enumerator identical to this one, but with the given maximum value.

enumerator

public static <A> Enumerator<A> enumerator(F<A,Option<A>> successor,
                                           F<A,Option<A>> predecessor,
                                           Option<A> max,
                                           Option<A> min,
                                           Ord<A> order,
                                           F<A,F<java.lang.Long,Option<A>>> plus)

Construct an enumerator. `

Parameters:

successor - The successor function.

predecessor - The predecessor function.

max - The potential maximum value.

min - The potential minimum value.

order - The ordering for the type.

plus - The function to move the enumeration a given number of times. This may be supplied for a performance enhancement for certain types.

Returns:

An enumerator with the given values.

enumerator

public static <A> Enumerator<A> enumerator(F<A,Option<A>> successor,
                                           F<A,Option<A>> predecessor,
                                           Option<A> max,
                                           Option<A> min,
                                           Ord<A> order)

Construct an enumerator. The plus function is derived from the successor and predecessor.

Parameters:

successor - The successor function.

predecessor - The predecessor function.

max - The potential maximum value.

min - The potential minimum value.

order - The ordering for the type.

Returns:

An enumerator with the given values.