gololang

Interface HeadTail<E>

Type Parameters:

E - the type of the elements held in this structure.

All Superinterfaces:

java.lang.Iterable<E>

All Known Subinterfaces:

Range<T>

All Known Implementing Classes:

LazyList, Tuple

public interface HeadTail<E>
extends java.lang.Iterable<E>

Structure having a head and a tail.

This interface can be used to define any recursive sequence of object, such as lists or generators. It is well suited to recursive algorithms, and thus can be seen as an alternative to the Iterable interface.

For example, one can compute the size of such an object with:

 static int size(HeadTail o) {
   if (o.isEmpty()) { return 0; }
   return 1 + size(o.tail());
 }
 

or in Golo:

 function size = |ht| -> match {
   when ht: isEmpty() then 0
   otherwhise 1 + size(ht: tail())
 }
 

Note that the size method is not provided since this interface can be implemented by infinite generators.

A List augmentation is provided, as well as corresponding special methods on arrays (Object[]/array[])

Method Summary

Modifier and Type	Method and Description
E	head() Get the head of the structure.
boolean	isEmpty() Checks if the structure is empty or not.
HeadTail<E>	tail() Get the tail of the structure.
static <E> java.lang.Iterable<E>	toIterable(HeadTail<E> headTail) Util method to wrap a HeadTail instance into an Iterable

Methods inherited from interface java.lang.Iterable

forEach, iterator, spliterator

Method Detail

head

E head()

Get the head of the structure.

Returns:

the first element of the structure, or null if the structure is empty.

tail

HeadTail<E> tail()

Get the tail of the structure.

To be side effect free, this method should return a deep copy of the original structure or an immutable view on it.

Returns:

a new HeadTail containing all the elements but the first, or a empty one if no elements remains.

isEmpty

boolean isEmpty()

Checks if the structure is empty or not.

Returns:

true if the structure contains no element, false otherwise.

toIterable

static <E> java.lang.Iterable<E> toIterable(HeadTail<E> headTail)

Util method to wrap a HeadTail instance into an Iterable

Parameters:

headTail - the instance to wrap

Returns:

an iterable on the values contained in the wrapped instance