duckie :)

data/scripts/types/list.lua

@@ -0,0 +1,98 @@
+---@class List
+local List = {}
+
+local function reduce(list, f, init)
+  local acc = init
+  for i, v in ipairs(list) do
+    acc = f(v, acc, i)
+  end
+  return acc
+end
+
+local function filter(list, predicate)
+  return reduce(list, function(el, acc, i)
+    if predicate(el) then
+      table.insert(acc, el)
+    end
+    return acc
+  end, List.create{})
+end
+
+local function shallow_copy(t)
+  local t2 = {}
+  for k, v in ipairs(t) do
+    t2[k] = v
+  end
+  return t2
+end
+
+List.__index = List
+setmetatable(List, {
+  __call = function(self, ...)
+    local args = {...}
+    if #args == 0 then
+      return List.create()
+    end
+
+    if type(args[1]) == "table" then
+      return List.create(args[1])
+    end
+    return List.create(args)
+  end
+})
+
+---Constructs a new list from the given table.
+---@param from table?
+---@return List
+function List.create(from)
+  from = from or {}
+  local l = shallow_copy(from)
+  return setmetatable(l, List)
+end
+
+function List:__tostring()
+  local s = "List(" .. table.concat(self, ", ", 1, #self) .. ")"
+  return s
+end
+
+---Appends v to the end of the list.
+---@param v any
+function List:push(v)
+  table.insert(self, v)
+end
+
+---Removes the last element in the list and returns it.
+---@return any
+function List:pop()
+  return table.remove(self, #self)
+end
+
+---Reduce.
+---@param f function called with element, accumulator, index
+---@param init any initial value of accumulator
+---@return any
+function List:reduce(f, init)
+  return reduce(self, f, init)
+end
+
+---Returns a new List of all elements of this list that match the predicate function.
+---@param predicate function called with element
+---@return List
+function List:filter(predicate)
+  return filter(self, predicate)
+end
+
+---Returns the index of value, if it exists in the list, -1 otherwise.
+---@param value any
+---@return integer
+function List:find(value)
+  local idx = -1
+  for i, v in ipairs(self) do
+    if v == value then
+      idx = i
+      break
+    end
+  end
+  return idx
+end
+return List