lua——基础语法

-- test lua: for learning lua grammar

-- line comment

--[[

	block comment

]]--

-- print hello world

print('Hello World\n')

-- control structure

-- if

if 1+1 == 2 then print('1+1=2') end

if 1+1 == 2 then

	print('1+1=2')

elseif 1+1 == 3  then

	print('1+1=3')

else

	print('1+1=?')

end

-- while

local n = 2

while n > 0 do

	print('while ' .. n)

	n = n - 1

end

-- repeat

n = 2

repeat

	print('repeat ' .. n)

	n = n - 1

until n <= 0

-- for

for i = 1, 2, 1 do

	print('for ' .. i)

end

-- for array

arr = {1, 2}

for i, v in ipairs(arr) do

	print('arr ' .. i .. ' ' .. v)

end

-- for table

t = {

	name = 'adfan',

	age = 20,

	[2] = 30,

}

for k, v in pairs(t) do

	print('table ' .. k .. ' = ' .. v)

end

-- assign

a, b, c, d = 1, 2, 3, 4

print(a, b, c, d)

-- exchange a, b

a, b = b, a

print(a, b)

-- math

print(2 ^ 4)	-- 2 power 4 = 16

-- compare

print(1 ~= 2)	-- not equal

-- logic

--[[

	Note: only false or nil are false, others are true (0 is alse true!)

		a and b: if a is false, return a; else return b (return the first false)

		a or b: if a is true, return a; else return b (return the first true)

]]--

print(true and 5)		-- 5

print(false and true)	-- false

print(true and 5 and 1)	-- 1

print(false or 0)		-- 0

print(nil or 1)			-- 1

print(not nil)			-- true

print(not 0)			-- false: as 0 is true

a, b, c = 1, nil, 3

x = a and b or c		-- not means a ?

b : c, as when b is false, x equals c..

print(x)

x = x or a				-- means if not x then x = v end

print(x)

-- opr inc order:

--[[

	or

	and

	< > <= >= ~= ==

	..(string plus)

	+ -

	* / %

	not #(get length) -

	^

]]--

-- var type

print('type nil ' .. type(nil))

print('type true ' .. type(true))

print('type 1 ' .. type(1))

print('type str ' .. type('adfan'))

print('type table ' .. type({1, 2, 3}))

print('type function ' .. type(function () end))

-- user data

-- local means local var, without local means global var

-- table

t = {

	10,		-- means [1] = 10

	[100] = 40,

	John = {

		age = 27,

		gender = male,

	},

	20		-- means [2] = 20

}

-- function

function add(a, b)

	return a + b

end

function sum(a, b, ...)

	c, d = ...

	print(...)

	print(a, b, c, d)

	return 14, 13, 12, 11

end

a, b, c, d = sum(1, 2, 3, 4)

print(a, b, c, d)