# Category talk:Wren-array

### Source code

```/* Module "array.wren" */

import "meta" for Meta
import "./check" for Check

/*
Array represents a List whose size cannot be changed after it has been constructed
but whose elements can be changed. If an array is created from a list, the
list is shallow-copied, not cloned.
*/
class Array is Sequence {
// Constructs a new array from a List or other Sequence.
construct from(a) {
Check.seq("Argument", a)
_a = a.toList // create a list or shallow copy if the argument is already a list.
}

// Constructs a new array from a List or other Sequence by fitting it to a given size
// truncating if it's too big or filling out with a given value if it's too small.
construct fit(size, a, v) {
Check.nonNegInt("Size", size)
Check.seq("Second argument", a)
a = a.toList
if (a.count == size) {
_a = a
} else if (a.count > size) {
_a = a[0...size]
} else {
_a = a
}
}

// Convenience version of 'fit' which uses a default value of null.
static fit(size, a) { fit(size, a, null) }

// Constructs a new array of a given size and sets all elements to the same value 'v'.
construct new(size, v) {
Check.nonNegInt("Size", size)
_a = List.filled(size, v)
}

// Convenience version of 'new' which sets all elements to null.
static new(size) { new(size, null) }

// Property
count { _a.count }  // returns the number of elements in the array

// Creates a shallow copy of the current instance.
copy() { Array.from(_a) }

// Resets all elements of the array to 'v'.
reset(v) {
for (i in 0..._a.count) _a[i] = v
}

// Gets the element at 'index.' If index is negative, it counts backwards
// from the end of the array where -1 is the last element.
// If index is a range it creates a new array from the appropriate elements.
[index] { (index is Range) ? Array.from(_a[index]) : _a[index] }

// Sets the element at 'index'. Negative indices are treated as in the getter.
[index]=(v) { _a[index] = v }

// Returns the index of 'value' in the current instance or -1 if 'value' is not found.
indexOf(value) { _a.indexOf(value) }

// Returns the index of the last occurrence of 'value' in the current instance
lastIndexOf(value) {
if (_a.count == 0) return 0
for (i in _a.count-1..0) {
if (_a[i] == value) return i
}
return -1
}

// Replaces all occurrences of 'old' by 'new' in the current instance
// and returns ['old', 'new'].
replace(old, new) {
for (i in 0..._a.count) {
if (_a[i] == old) _a[i] = new
}
return [old, new]
}

// Sorts the elements of the array in place and both overloads work in exactly
// the same manner as the corresponding methods in the List class.
sort()         { _a.sort() }
sort(comparer) { _a.sort(comparer) }

// Swaps the elements at index1 and index2 within the array.
swap(index1, index2) { _a.swap(index1, index2) }

// Applies a function to each element of the array.
apply(fn) {
Check.func("fn", fn, 1)
for (i in 0..._a.count) _a[i] = fn.call(_a[i])
}

// Iterator protocol methods.
iterate(iterator) { _a.iterate(iterator) }
iteratorValue(iterator) { _a.iteratorValue(iterator) }

// Returns the string representation of the underlying list.
toString { _a.toString }
}

/*
ArrayType creates a named class which inherits from Array and always has the same
size and default values. The named class has four constructors:
1. new(v)    - sets all elements to 'v'
2. new()     - sets all elements to the default value
3. fit(a, v) - fits the sequence 'a' to 'size' filling out with 'v' if too short
4. fit(a)    - as (3) but fills out with the default value if too short
and four instance methods of its own:
5. default   - returns the default value
6. toArray   - converts the current instance to an Array
7. copy()    - creates a shallow copy of the current instance
- overriding the copy() method inherited from Array
8. reset()   - resets all elements to the default value.
*/
class ArrayType {
// Creates a class for the ArrayType (with an underscore after the name), with a
// given size and default value for its elements, and returns a reference to it.
static create(name, size, default) {
Check.ident("Name", name)
Check.nonNegInt("Size", size)
name = name +  "_"
var s = "class %(name) is Array {\n"
s = s + "    construct new(v) {\n"
s = s + "        super(%(size), v)\n"
s = s + "    }\n"
s = s + "    construct new()  {\n"
s = s + "        super(%(size), %(default))\n"
s = s + "    }\n"
s = s + "    construct fit(a, v) {\n"
s = s + "        super(%(size), a, v)\n"
s = s + "    }\n"
s = s + "    construct fit(a) {\n"
s = s + "        super(%(size), a, %(default))\n"
s = s + "    }\n"
s = s + "    default { %(default) }\n"
s = s + "    toArray() { Array.from(this) }\n"
s = s + "    copy() {\n"
s = s + "        var d = %(name).new()\n"
s = s + "        for (i in 0...%(size)) d[i] = this[i]\n"
s = s + "        return d\n"
s = s + "    }\n"
s = s + "    reset() { reset(%(default)) }\n}\n"
s = s + "return %(name)"
return Meta.compile(s).call()
}

// Convenience version of 'create' which always uses a default value of null.
static create(name, size ) { create(name, size, null) }
}

/*
BitArray represents a List<Bool> whose size cannot be changed after it has been constructed
but whose elements can be changed. It uses only 1/32nd as much memory as a 'normal' List<Bool>
but is around 4 times slower to index. Also, unlike List<Bool>, BitArray is not a Sequence.
*/
class BitArray {
// Constructs a new BitArray of a given size and sets all elements to the same value 'v'.
// 'size' is rounded to the higher multiple of 32 where necessary.
construct new(size, v) {
Check.posInt("size", size)
Check.bool("value", v)
_len = (size / 32).ceil
_a = List.filled(_len, v ? 4294967295 : 0)
}

// Convenience version of 'new' which sets all elements to false.
static new(size) { new(size, false) }

// Returns the number of elements in the BitArray.
count { 32 * _len }

// Creates a copy of the current instance.
copy() {
var c = BitArray.new(count, false)
for (i in 0...count) c[i] = this[i]
return c
}

// Resets all elements of the BitArray to 'v'.
reset(v) {
Check.bool("value", v)
var value = v ? 4294967295 : 0
for (i in 0..._len) _a[i] = value
}

// Gets the element at 'index'. If index is negative, it counts backwards
// from the end of the array where -1 is the last element.
// To maximize access speed, this method doesn't validate the index.
// Use the 'get' method instead if you need to do that.
[index] {
if (index < 0) index = count + index
var ix = (index/32).floor
var bit = index%32
return ((_a[ix] >> bit) & 1) == 1
}

// Sets the element at 'index'. Negative indices are treated as in the getter.
// To maximize access speed, this method doesn't validate the index nor the new value.
// Use the 'set' method instead if you need to do that.
[index]=(v) {
if (index < 0) index = count + index
var ix = (index/32).floor
var bit = index%32
_a[ix] = v ?  _a[ix] | (1 << bit) : _a[ix] & ~(1 << bit)
}

// As [index] method but validates the index.
get(index) {
Check.int("index", index, -count, count-1)
return this[index]
}

// As [index]=(v) method but validates the index and the new value.
set(index, v) {
Check.int("index", index, -count, count-1)
Check.bool("value", v)
this[index] = v
}

// Returns a List<Bool> using the normal 8 bytes for each element.
toList {
var bools = List.filled(count, false)
for (i in 0...count) bools[i] = this[i]
return bools
}

// Returns an Array<Bool> using the normal 8 bytes for each element.
toArray {
var bools = Array.new(count, false)
for (i in 0...count) bools[i] = this[i]
return bools
}

// Returns a bit string representation of this BitArray.
toString {
var bytes = List.filled(count, 0)
for (i in 0...count) if (this[i]) bytes[i] = 1
return bytes.join()
}
}
```