Programming-Idioms.org

print("Hello World")

io.write("Hello world")

for i=1, 10 do
	print('Hello')
end

print(("Hello\n"):rep(10))

print(string.rep("Hello\n", 10))

local i = 0
repeat
	i = i + 1
	print("Hello")
until i == 10

function finish(name)
	print('My job here is done. Goodbye, '..name..'.')
end

function square(x)
	return x*x
end

point = { x = 123, y = 456 }

for _, x in ipairs(items) do
	print(x)
end

for i, x in ipairs(items) do
	print('Index: '..i..', Value: '..x)
end

x = {one = 1, two = 2}

local function BinTree(v, l, r)
	return {
		val = v,
		left = l,
		right = r
	}
end

shuffled = {}
for i, v in ipairs(x) do
	local pos = math.random(1, #shuffled+1)
	table.insert(shuffled, pos, v)
end

function(x)
	for i = #x, 2, -1 do
		local j = math.random(i)
		x[i], x[j] = x[j], x[i]
	end
end

x[math.random(#x)]

function contains(list, x)
	for _, v in ipairs(list) do
		if v == x then return true end
	end
	return false
end

for k, x in pairs(mymap) do
	print('Key: '..k..', Value: '..x)
end

function pick(a,b)
	return a + (math.random()*(b-a))
end

math.random(a, b)

local function dfs(bt, f, ...)
  local tt = type(bt)
  if tt~='table' and tt~='userdata' then return end
  dfs(t.left, f, ...)
  f(t.data, ...)
  dfs(t.right, f, ...)
end

local function Tree(v, c)
	return {
		val = v,
		children = c
	}
end

rev = {}
for i=#x, 1, -1 do
	rev[#rev+1] = x[i]
end
x = rev

rev = {}
for i=#x, 1, -1 do
	rev[#rev+1] = x[i]
end

-- in-situ reversal
function reverse(t)
  local n = #t
  local i = 1
  for i = 1, n do
    t[i],t[n] = t[n],t[i]

    n = n - 1
  end
end

function array_reverse(x)
  local n, m = #x, #x/2
  for i=1, m do
    x[i], x[n-i+1] = x[n-i+1], x[i]
  end
  return x
end

function search(m, x)
   for i,v1 in ipairs(m) do
      for j,v2 in ipairs(v1) do
         if v2 == x then return i,j end
      end
   end
end

a, b = b, a

i = tonumber(s)

s = string.format("%.2f",x)

s = 'ネコ'

local x = setmetatable({},{
   __index = function(t1,k1)
      t1[k1] = setmetatable({},{
         __index = function(t2,k2)
            t2[k2] = 0
            return t2[k2]
         end
      })
      return t1[k1]
   end
})

x = {}
for i=1,m do
  x[i] = {}
  for j=1,n do
    x[i][j] = 0
  end
end

local x = {}
for i=1,m do
   x[i] = {}
   for j=1,n do
      x[i][j] = {}
      for k=1,p do
         x[i][j][k] = 0
      end
   end
end

table.sort(items, function(a,b)
	if a.p < b.p then return true end
end)

local removedItem = table.remove(items,i)

function f(n)
   local function f_(factorial,n)
      if n < 2 then return 1
      return f_(factorial*n, n-1)
   end
   return f_(1,n)
end

function exp(x, n)
    return x^n
end

function compose(f,g)
   return function(x)
      return g(f(x))
   end
end

function compose(f,g)
   return function(x)
      return g(f(x))
   end
end

function curry2(f)
   return function(a)
      return function(b)
         return f(a,b)
      end
   end
end

function add(a,b)
   return a + b
end

local curryAdd = curry2(add)
local add2 = curryAdd(2)

local unpack = unpack or table.unpack
local function aux_ncurry(n, m, fn, args)
  if m>n then return fn(unpack(args,1,n))end
  local new_args, new_m = {}, m
  for i=1,m-1 do new_args[i]=args[i]end
  return function(a) 
    new_args[new_m]=a
    return aux_ncurry(n, new_m + 1, fn, new_args)
  end
end
local function ncurry(n, fn) return aux_ncurry(n,1,fn,{}) end

local t = s:sub(i, j - 1)

ok = s:find(word, 1, true)

ok = false
if s:find(word, 1, true) then ok = true end

ok = s:find(word, 1, true) ~= nil

function utf8.reverse(s)
	local r = ""
	for p,c in utf8.codes(s) do
		r = utf8.char(c)..r
	end
	return r
end

t = utf8.reverse(s)

breakout = false
for i,v1 in ipairs(m) do
   for j,v2 in ipairs(v1) do
      if v2 < 0 then
         print(v2)
         state = "found"
         breakout = true
         break
      end
   end
   if breakout then break end
end

for _,v1 in ipairs(m) do
 for _,v2 in ipairs(v1) do
  if v2<0 then
   print(v2)
   goto outer
  end
 end
end
::outer::

table.insert(s,i,x)

local start = os.clock()
while os.clock() - start < 5 do end

os.execute(package.config:sub(1,1) == "/" and "sleep 5" or "timeout 5")

t = s:sub(1,5)

s = [[
Huey
Dewey
Louie
]]

s = 'Huey \n'..
'Dewey \n'..
'Louie'

chunks = {}
for substring in s:gmatch("%S+") do
   table.insert(chunks, substring)
end

while true do 
	-- Do something
end

::loop::
goto loop

repeat
until false

m[k] ~= nil

y = table.concat(x, ", ")

s = 0
for i,v in ipairs(x) do
   s = s + v
end

s = tostring(i)

y = {}
for _, v in ipairs(x) do
	if p(v) then y[#y+1] = v end
end

local y={}
for _,v in ipairs(x) do
 if p(v)==true then 
  table.insert(y,v)
 end
end

lines = io.input(f):read('a')

io.stderr:write(string.format("%d is negative\n",x))

x = arg[1]

d = os.date()

i = x:find(y)

x2 = x:gsub(y,z)

s = string.format("%.1f%%", x*100)

local s = (x-x%10^-3)*100 .."%"

math.randomseed(s)

math.randomseed( os.time() )

print( table.concat( arg, " " ) )

function gcd(x, y)
	if (y == 0) then
		return x
	else 
		return gcd(y, x%y)
	end
end

function gcd(a, b)
	return b==0 and a or gcd(b,a%b)
end

local s = {}

while x > 0 do
    local tmp = math.fmod(x,2)
    s[#s+1] = tmp
    x=(x-tmp)/2
end

s=table.concat(s)

repeat
	someThing()
	someOtherThing()
until not c

y = x + .0

y = (16 ^ 13) + x - (16 ^ 13)

y = math.modf(x)

function round(float)
    local int, part = math.modf(float)
    if float == math.abs(float) and part >= .5 then return int+1    -- positive float
    elseif part <= -.5 then return int-1                            -- negative float
    end
    return int
end

function round(float)
    return math.floor(float + .5)
end

r = "htt+p"

local function intadding_will_overflow(x,y)
 return x>0
  and y>0 and x+y<x
  or y<0 and x+y>x
end

os.exit()

return

return nil, "Invalid argument x"

error("Invalid argument x")

local Foo = {}
do
	local x = 0
	Foo.getX = function()
		return x
	end
end
print(Foo.getX()) -- 0
print(x) -- nil

local function Foo()
    local private = {x = 9}
    local mt = {
        __index = private,
        __newindex = function (t, k, v)
            error("attempt to update a read-only table", 2)
        end
    }
    return setmetatable({}, mt)
end

local foo = Foo()
print(foo.x) -- 9
foo.x = 3    -- error: attempt to update a read-only table

file = io.open("data.json")
x = cjson.decode(file:read("a"))
file:close()

file = io.open("data.json", "w")
file:write(cjson.encode(x))
file:close()

function control(f)
	f()
end

print(type(x))

b = s:find(prefix, 1, true) == 1

function startswith(text, prefix)
    return text:find(prefix, 1, true) == 1
end

b = startswith(s, prefix)

b = string.sub(s, 1, #prefix) == prefix

b = s:sub(-string.len(suffix)) == suffix

x = os.date("%F",d)

table.sort(items,c)

s = arg[0]

dir = os.getenv("PWD") or io.popen("cd"):read()

dir = arg[1]

if x then print(x) end

 blank = (s == nil or #string.gsub(s, "^%s*(.-)%s*$", "%1") == 0)

os.execute(x .. 'a b')

for k, x in pairs(mymap) do
  print(k, x)
end

s2 = s1:gsub(w,"")

local n = #x

local hash = {}
local y = {}
for _,v in ipairs(x) do
   if (not hash[v]) then
       y[#y+1] = v
       hash[v] = true
   end
end

local seen = {}
for index,item in ipairs(x) do
	if seen[item] then
		table.remove(x, index)
	else
		seen[item] = true
	end
end

n = io.read("n")

Suit = {
    SPADES=1,
    HEARTS=2,
    DIAMONDS=3,
    CLUBS=4
}

assert(isConsistent() , "Assertion violation") 

function foo()
	return "bar", false
end

if (c1) then f1()
elseif (c2) then f2()
elseif (c3) then f3()
end

ok = string.find(string.lower(s), string.lower(word)) and true or false

local ok=string.find(string.lower(s),string.lower(word),nil,true)~=nil

items = {a, b, c}

b = tonumber(s) ~= nil

file = io.tmpfile()

m[k]=nil

s = string.format("%x",x)

p = string.gsub(p,"/$","")

if string.sub(p, -1, -1) == "/" then
	p=string.sub(p, 1, -2)
end

s = c

t = s .. i

local c = "#"
for i=2,#c1,2 do
	local avg = (tonumber(c1:sub(i,i+1), 16) + tonumber(c2:sub(i,i+1), 16)) / 2
	c = c .. string.format("%02x", math.floor(avg))
end

os.remove(filepath)

string.format("%03d", i)

PLANET = "Earth"

local function New(base,new)
 return setmetatable(new,{__index=base})
end
local Trie={}
function Trie.New()
 return New(Trie,{
  children={},
  value=nil
 })
end

local function map(t,fn)
 for i,v in ipairs(t) do
  t[i]=fn(v)
 end
 return t
end

local ret=map(elements,function(x) return x*c end)

local x = items[#items]

ab = {}

table.foreach(a, function(k, v) table.insert(ab, v) end)
table.foreach(b, function(k, v) table.insert(ab, v) end)

ab = {}

table.move(a, 1, #a, 1, ab)
table.move(b, 1, #b, #ab + 1, ab)

local t = (s:sub(0, #p) == p) and s:sub(#p+1) or s

local t = s:gsub(w.."$", "")

local n = utf8.len(s)

local utf8={}
function utf8.bytes(str,index)
 local byte=string.byte(str,index)
 local ret
 if     byte==nil then ret=0
 elseif byte<128  then ret=1
 elseif byte<192  then ret=2
 elseif byte<224  then ret=3
 else                  ret=4
 end
 return ret
end
function utf8.len(str)
 local count=0
 local fini=#str+1
 local index=1
 while index~=fini do
  count=count+1
  index=index+utf8.bytes(str,index)
 end
 return count
end
local n=utf8.len(s)

local n=0
for _ in pairs(mymap) do n=n+1 end

s[#s + 1] = x

table.insert(s, x)

for i,v in ipairs(a) do
 a[i]=string.format("%02x",v)
end
local s=table.concat(a)

x = [["x = [" .. "[" .. x .. "]" .. "]\nprint(" .. x)]]
print("x = [" .. "[" .. x .. "]" .. "]\nprint(" .. x)

os.exit(0)

local a = {}

for x = 1, n do
  local t = {}
  for y = 1, m do
    t[y] = {x, y}
  end
  a[x] = t
end
  
local b = {}

for y = 1, m do
  local t = {}
  for x = 1, n do
    t[x] = a[x][y]
  end
  b[y] = t
end

os.exit(x)

local h = math.sqrt(x^2 + y^2)

local h=(x^2+y^2)^0.5

local function frexp(a)
	return math.frexp(a)
end

foo = os.getenv("FOO") or "none"

local procedures={
 foo=function() end,
 bar=function() end,
 baz=function() end,
 barfl=function() end,
}
local function process(str)
 local procedure=procedures[str]
 if procedure~=nil then
  procedure()
 end
end
process(str)

print(_VERSION)

local t = s:gsub("%s+", " ")

local function list_cond(t,cond)
 for _,v in ipairs(t) do
  if cond(v)==true then return true end
 end
 return false
end
if list_cond(items,function(x) return x==0 end) then
 print("did find 0")
else
 print("didn't find 0")
end

table.insert(items, 1, x)

function f( x )
	if x then
		print("Present", x)
	else
		print("Not present")
	end
end

local function deepcopy(input)
 local t=type(input)
 if t~="table" then
  return input
 end
 local copy={}
 for k,v in pairs(input) do
  k=deepcopy(k)
  v=deepcopy(v)
  copy[k]=v
 end
 return copy
end
local y=deepcopy(x)

local c = {}
for i=1,#a do
	c[i] = string.char(string.byte(a, i) ~ string.byte(b, i))
end
c = table.concat(c)

print(table.concat(a,", "))

local c=#items

for i=5, 0, -1 do
	print(i)
end

s = string.rep(v, n)

local Vector={x=0,y=0,z=0}
---@type metatable
local mt={
 __index=Vector,
}
function mt.__add(a,b)
 return Vector.new(
  a.x+b.x,
  a.y+b.y,
  a.z+b.z
 )
end
function Vector.new(x,y,z)
 return setmetatable({x=x,y=y,z=z},mt)
end

n=1
while(n<=100) do
    out=""
    if(n%3==0) then
        out=out .. "Fizz"
    end
    if(n%5==0) then
        out=out .. "Buzz"
    end
    if(out=="") then
        out=out .. tostring(n)
    end
    print(out)
    n=n+1
end

for n=1,100 do
 print(
  n%3==0
  and (n%5==0 and "FizzBuzz" or "Fizz")
  or (n%5==0 and "Buzz")
  or tostring(n)
 )
end

x[e] = true

local map={[Foo]=true}

local function split(s,sep)
 local parts={}
 for sub in string.gmatch(s,"[^"..sep.."]+") do
  table.insert(parts,sub)
 end
 return parts
end

local function new_zeroed_list(n)
 local ret={}
 for i=1,n do
  ret[i]=0
 end
 return ret
end
local zeroed_list=new_zeroed_list(n)

local a = 0/0

local s = a..b

local function erase(t,i,j)
 for i=1,j-1 do
  t[i]=nil
 end
end
erase(items,i,j)

-- This is a comment

local str=string.format("Our sun has %d planets",x)

local t = string.lower(s)

local t = string.upper(s)

local v=m[k]

local m={}
for _,e in ipairs(a) do
 m[e.id]=e
end