Lulu Arrays — Metamethods etc.

Introduction

If you have imported the lulu.Array class as

local Array = require 'lulu.Array'

then you have access to the following methods & metamethods.

Array:is_instance(obj)
Returns true if obj is an instance of the Array class or a subclass.

Array:name()
Returns self.__name which is just Array for the base class.

Array.__call
This make any Array(...) call a synonym for Array:new.

Array.__eq
If a and b are Array instances this points code lke a == b and a ~= b use Array:eq under the covers.

Array.__tostring
If a is an Array instance this points code lke print(a) or tostring(a) to {Array.tostring} under the covers.

Array.__name
This is a piece of string data occasionally used by Lua and also returned by the Array:name() method above. It is set to “Array” for the base class.

Array.__concat
If a and b are Array instances then we have overloaded a .. b to return a:copy():append(b).

Example

1local CheckedArray = Array:subclass("CheckedArray")
local a = Array{1,2,3}
local c = CheckedArray{1,2,3}
putln("a is an '%s' with values: %t", a:name(), a)
putln("c is a '%s' with values: %t", c:name(), c)

1: Create CheckedArray as a subclass of Array.

Output

a is an 'Array' with values: [ 1, 2, 3 ]
c is a 'CheckedArray' with values: [ 1, 2, 3 ]

Note that any CheckedArray is also an Array but not vice-versa:

putln("a is an Array:       %s", Array:is_instance(a))
putln("c is an Array:       %s", Array:is_instance(c))
putln("a is a CheckedArray: %s", CheckedArray:is_instance(a))

Output

a is an Array:       true
c is an Array:       true
a is a CheckedArray: false

Example: Concatenation

local a = Array{1,2,3}
local b = Array{3,4,5}
local c = a .. b
putln("a: %t", a)
putln("b: %t", b)
putln("c: %t", c)

Output: Concatenation

1a: [ 1, 2, 3 ]
2b: [ 3, 4, 5 ]
3c: [ 1, 2, 3, 3, 4, 5 ]

1: a is unchanged.
2: b is unchanged.
3: c has the same elements as a:append(b) so there is duplication in this instance.

Introduction

See Also