Lua

tags: programming-language lua

Lua

コメント

-- comment

--[[
multiple line comment
ok.
]]

変数

-- num
x = 10
x = 1.0
x = 10e-1

-- string
s = "AAA"
s = 'AAA\n'

-- function
function square(x)
  return x * x
end

-- table
t = {}

-- boolean
b = true
b = false

テーブル

t = {}
t["str"] = "string"
t["boolean"] = false
t["number"] = 1

-- number is accepted as index
-- index should start from 1, lua expects that beginning of index is 1.
t[1] = "one"
t[2] = true
t[3] = 3

イテレータ

t = {}
t["1"] = "one"
t["2"] = "two"
t["3"] = "three"

for i, val in pairs(t) do -- i <- index, val <- value
    print(i, val)
end   

t[1] = "one"
t[2] = "two"
t[3] = "three"

for i, val in ipairs(t) do -- if index is num, can use ipairs
    print(i, val) -- output "one", "two", "three"
end

演算子

-- math
1 + 3
1 - 3
1 * 2
1 / 13
1 ^ 0
1 % 2

-- cmp
1 < 2
1 > 4
1 <= 2
1 >= 1
1 == 1
1 ~= 1 -- not equal

-- logical
true and true
true or false
not false

-- string
"str1" .. "str2" -- "str1str2"

if

a = 3
b = 2

if a > b then
    print("a")
end

if a > b then
    print("a")
elseif a == b then
    print("ab")
else
    print("b")
end 

for

for i = 0, 4, 1 do
    print(i) -- 0, 1, 2, 3, 4
end

a = 0
b = 4
while a <= b do
    print(a) -- 0, 1, 2, 3, 4
    a = a + 1
end

a = 0
b = 5
repeat
    print(a) -- 0, 1, 2, 3, 4
    a = a + 1
until a == b

while true do
    break -- break should be before end
end

while true do
    do
        break
    end
    
    a = 10
end

関数

function funcname (arg)
    return arg + 1
end

function returnmultival(arg1, arg2)
    return arg1, arg2
end

a, b = returnmultival(1, 2)

-- extendable arg
function func(...)
    t = {...}
end

-- lambda
f = function(args)
       return args
    end
    
f(3)

コルーチン(co-routine)

function col(a, b, c)
    sum = 0
    sum = sum + a
    coroutine.yield(sum)
    sum = sum + b
    coroutine.yield(sum)
    sum = sum + c   
    return sum
end 

local co = ccoroutine.wrap(col)
ret = co(3, 2, 1) -- return a ?
ret = co(3, 2, 1) -- return a + b
ret = co(3, 2, 1) -- return a + b + c