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Object-oriented programming (in Lua)

Time and time again, programming newcomers struggle with grasping the essence of OOP, often confusing it with particularly restrictive implementations. Additionally, Lua newcomers struggle to understand how to implement OOP in Lua, often blindly copying "patterns" and expecting to miraculously obtain whatever they believe is OOP. This is an attempt to clear both up.

Objects

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-- Usage: luajit bench.lua (closures|metatables)
local Foobar = require((...))
for _ = 1, 5 do
	local t = os.clock()
	local sum = 0
	for i = 1, 1e6 do
		sum = sum + Foobar("foo", i, "baz"):get_bar()
	end
	print("dt", os.clock() - t, "sum", sum)
end

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--[[
	Randomize `pairs` traversal order to deliberately break code that relies on it.
	Works by doing a coin toss to decide whether to "postpone" visiting the first entry
	(visiting it at the end of the traversal).
	Shuffling all keys, then iterating in that shuffled order would provide more thorough randomization; however:
	* It is less efficient if the loop is exited early; it may arbitrarily wreck performance
	  (consider a large table where `pairs` is only used to inspect very few entries.)
	* I believe this simple solution already suffices for most code
	  that incorrectly relies on a specific order of traversal.
	  Notably, this has a 50% chance of breaking code that

appgurueu

local jobs = {}

minetest.register_globalstep(function(dtime)
	local remaining_jobs = {}
	local time_per_job = dtime / #jobs
	for _, job in ipairs(jobs) do
		local time_s = minetest.get_us_time() / 1e6
		repeat
			assert(coroutine.resume(job))
			local dtime_s = minetest.get_us_time() / 1e6 - time_s

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local eye_pos = player:get_pos()
eye_pos.y = eye_pos.y + player:get_properties().eye_height
local first, third = player:get_eye_offset()
if not vector.equals(first, third) then minetest.log("warning", "First & third person eye offsets don't match, assuming first person") end
eye_pos = vector.add(eye_pos, vector.divide(first, 10))
local def = player:get_wielded_item():get_definition()
for pointed_thing in minetest.raycast(eye_pos, vector.add(eye_pos, vector.multiply(player:get_look_dir(), def.range or 4)), true, def.liquids_pointable) do if pointed_thing.ref ~= player then --[[do something]] end end

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-- Longest common prefix of any two strings in `strs`
local function lcp(strs)
    assert(#strs >= 2)
    local trie = {}
    local max_cp_len = 0
    local max_cp_node = trie
    for i, str in ipairs(strs) do
        local cp_len = 0
        local cp_node = trie
        while cp_len < #str do

appgurueu

-- Use a modified mergesort to count the inversions summing up to `x`
local function count_x_inversions(
	list, -- of distinct nums
	x -- target sum
)
	local function merge(result, left, right)
		local inversions = 0
		local i, j, k = 1, 1, 1
		local left_idx = {}
		for idx, v in ipairs(left) do

appgurueu

import "sort"

// This is not particularly efficient.
// A more efficient implementation might either be B-Tree like,
// might eliminate the index, might distinguish parents and leaves,
// and might strip parents of their values;
// to alleviate the mem management overhead, I'd wish
// for an arena allocator, but this isn't Zig

type PSlice[T any] struct {

appgurueu

#!/usr/bin/env luajit
-- See https://content.minetest.net/help/api/
local http_request = require"http.request"
local lunajson = require"lunajson"

do
	-- URI escaping utilities
	-- See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/encodeURI

	local uri_unescaped_chars = {}

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# Rules for programs which must run under both LuaJIT and PUC Lua 5.1
# and which thus may not rely on the 5.2 LuaJIT compatibility features
# See http://luajit.org/extensions.html
rules:
  - id: xpcall-args
    pattern-either:
      # theoretically could be fine e.g. if (empty vararg!), but practically never is
      - pattern: xpcall($FN, $ERRHAND, $EXP, ...)
      # the following could also theoretically be fine, but practically are a major code smell
      - pattern: xpcall($FN1, $FN2(...))