86 lines
3.8 KiB
Markdown
86 lines
3.8 KiB
Markdown
# Iterable interface
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The interface for anything that can be iterated, e.g. finite or infinite ordered set of data that can be accessed sequentially. Almost any data container in `Lyng` implements it: `List`, `Set`, `Buffer`, `RingBuffer`, `BitBuffer`, `Range` and many others are `Iterable`, also `Collection` and `Array` interfaces inherit it.
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`Map` and `String` have `Iterable` members to access its contents too.
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## Definition:
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Iterable is a class that provides function that creates _the iterator_:
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class Iterable {
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abstract fun iterator()
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}
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Note that each call of `iterator()` must provide an independent iterator.
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Iterator itself is a simple interface that should provide only to method:
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class Iterator {
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abstract fun hasNext(): Bool
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fun next(): Obj
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}
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Just remember at this stage typed declarations are not yet supported.
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Having `Iterable` in base classes allows to use it in for loop. Also, each `Iterable` has some utility functions available, for example
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val r = 1..10 // Range is Iterable!
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assertEquals( [9,10] r.takeLast(2) )
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assertEquals( [1,2,3] r.take(3) )
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assertEquals( [9,10] r.drop(8) )
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assertEquals( [1,2] r.dropLast(8) )
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>>> void
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## Instance methods:
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| fun/method | description |
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|-----------------|---------------------------------------------------------------------------------|
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| toList() | create a list from iterable |
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| toSet() | create a set from iterable |
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| contains(i) | check that iterable contains `i` |
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| `i in iterator` | same as `contains(i)` |
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| isEmpty() | check iterable is empty |
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| forEach(f) | call f for each element |
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| toMap() | create a map from list of key-value pairs (arrays of 2 items or like) |
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| map(f) | create a list of values returned by `f` called for each element of the iterable |
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| indexOf(i) | return index if the first encounter of i or a negative value if not found |
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| associateBy(kf) | create a map where keys are returned by kf that will be called for each element |
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| first | first element (1) |
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| last | last element (1) |
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| take(n) | return [Iterable] of up to n first elements |
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| taleLast(n) | return [Iterable] of up to n last elements |
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| drop(n) | return new [Iterable] without first n elements |
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| dropLast(n) | return new [Iterable] without last n elements |
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(1)
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: throws `NoSuchElementException` if there is no such element
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fun Iterable.toList(): List
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fun Iterable.toSet(): Set
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fun Iterable.indexOf(element): Int
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fun Iterable.contains(element): Bool
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fun Iterable.isEmpty(element): Bool
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fun Iterable.forEach(block: (Any?)->Void ): Void
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fun Iterable.map(block: (Any?)->Void ): List
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fun Iterable.associateBy( keyMaker: (Any?)->Any): Map
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## Abstract methods:
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fun iterator(): Iterator
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Creates a list by iterating to the end. So, the Iterator should be finite to be used with it.
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## Included in interfaces:
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- [Collection], Array, [List]
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## Implemented in classes:
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- [List], [Range], [Buffer](Buffer.md), [BitBuffer], [Buffer], [Set], [RingBuffer]
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[List]: List.md
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[Range]: Range.md
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[Set]: Set.md
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[RingBuffer]: RingBuffer.md |