Module:FunList/Iterators: Difference between revisions
From Melvor Idle
(Add WhereEnumerator) |
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return self | return self | ||
else | else | ||
return WhereEnumerator.new(self.source, self. | return WhereEnumerator.new(self.source, self.predicate) | ||
end | end | ||
end | end |
Revision as of 18:35, 21 July 2024
Documentation for this module may be created at Module:FunList/Iterators/doc
-- BASE ENUMERATOR CLASS --
--enumerable = {}
local Enumerator = {}
local Enumerator_mt = {
__index = Enumerator,
__pairs = function(t) return t:overridePairs() end,
--__ipairs = function(t) return t:overrideiPairs() end
}
function Enumerator.new()
local self = setmetatable({}, Enumerator_mt)
self.current = nil
self.index = nil
return self
end
function Enumerator:moveNext()
error('Not implemented in base class.')
end
function Enumerator:getEnumerator()
error('Not implemented in base class.')
end
-- Hooks the moveNext function into the Lua 'pairs' function
function Enumerator:overridePairs()
self.index = nil
self.current = nil
local function iterator(t, k)
if self:moveNext() == true then
return self.index, self.current
end
return nil, nil
end
return iterator, self, nil
end
-- TABLE ENUMERATOR CLASS --
-- This is essentially a wrapper for the table object,
-- since it provides no state machine esque iteration out of the box
local TableEnumerator = setmetatable({}, { __index = Enumerator })
TableEnumerator.__index = TableEnumerator
TableEnumerator.__pairs = Enumerator_mt.__pairs
function TableEnumerator.new(tbl)
local self = setmetatable(Enumerator.new(), TableEnumerator)
self.tbl = tbl
return self
end
function TableEnumerator:moveNext()
if self.state == 0 then
self.state = 1
end
-- Grab the next index for the internal table.
local key = self.index
key = next(self.tbl, key)
self.index = key
-- If the index exist, we have succesfuly moved to the next.
if key ~= nil then
self.current = self.tbl[key]
return true
end
return false
end
function TableEnumerator:getEnumerator()
if self.state == 0 then
return self
else
return TableEnumerator.new(self.tbl)
end
end
-- SELECT ENUMERATOR --
local SelectEnumerator = setmetatable({}, { __index = Enumerator })
SelectEnumerator.__index = SelectEnumerator
SelectEnumerator.__pairs = Enumerator_mt.__pairs
function SelectEnumerator.new(source, selector)
local self = setmetatable(Enumerator.new(), SelectEnumerator)
self.state = 0
self.source = source
self.selector = selector
self.enumerator = nil
self.position = 0
return self
end
function SelectEnumerator:moveNext()
if self.state == 0 then
self.state = 1
self.position = 0
self.enumerator = self.source:getEnumerator()
end
if self.state == 1 then
local enumerator = self.enumerator
if enumerator:moveNext() == true then
local sourceElement = enumerator.current
self.index = enumerator.index -- Preserve index
self.position = self.position + 1
self.current = self.selector(sourceElement, self.position)
assert(self.current, 'Selected value must be non-nil')
return true
end
end
return false
end
function SelectEnumerator:getEnumerator()
if self.state == 0 then
return self
else
return SelectEnumerator.new(self.source, self.selector)
end
end
-- WHERE ENUMERATOR --
local WhereEnumerator = setmetatable({}, { __index = Enumerator })
WhereEnumerator.__index = WhereEnumerator
WhereEnumerator.__pairs = Enumerator_mt.__pairs
function WhereEnumerator.new(source, predicate)
local self = setmetatable(Enumerator.new(), WhereEnumerator)
self.state = 0
self.source = source
self.predicate = predicate
self.enumerator = nil
return self
end
function WhereEnumerator:moveNext()
if self.state == 0 then
self.state = 1
self.position = 0
self.enumerator = self.source:getEnumerator()
end
if self.state == 1 then
local enumerator = self.enumerator
while enumerator:moveNext() == true do
local sourceElement = enumerator.current
if self.predicate(sourceElement) == true then
self.index = enumerator.index
self.current = sourceElement
return true
end
end
end
return false
end
function WhereEnumerator:getEnumerator()
if self.state == 0 then
return self
else
return WhereEnumerator.new(self.source, self.predicate)
end
end
return {
Enumerator = Enumerator,
TableEnumerator = TableEnumerator,
SelectEnumerator = SelectEnumerator,
WhereEnumerator = WhereEnumerator
}