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list.lua
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list.lua
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local Enumerable = require 'enumerable'
local Collectable = require 'collectable'
local Iterator = require 'iterator'
local List = {}
List.__index = List
setmetatable(List, { __call = function(_, ...) return List.new(...) end })
function List.new()
local self = setmetatable({}, List)
return self
end
function List.iterator(list)
return Iterator.new(ipairs(list))
end
-- Collectable Protocol
--- IMPURE function
local collector = function(collection, cmd, value)
if cmd == "cont" then
table.insert(collection, value)
return collection
elseif cmd == "done" then
return collection
elseif cmd == "halt" then
return collection
end
end
function List.into() List.into(List.new()) end
function List.into(initial) return initial, collector end
-- Enumerable Protocol
function List.reduce(list, reducer, cmd, acc)
return List.do_reduce(List.iterator(list), reducer, cmd, acc)
end
function List.do_reduce(iter, reducer, cmd, acc)
assert(iter)
if cmd == "halt" then
return "halted", acc
elseif cmd == "suspend" then
return "suspended", acc, function(cmd, acc)
List.reduce(iter, reducer, cmd, acc)
end
elseif cmd == "cont" then
local val = Iterator._next(iter)
-- val[1] is the key/index, we want the value
local state = val[2]
if state == nil then
return "done", acc
else
cmd, acc = reducer(state, acc)
return List.do_reduce(iter, reducer, cmd, acc)
end
end
end
Enumerable:_impl(List)
Collectable:_impl(List)
return List