lua——基础语法

-- test lua: for learning lua grammar

-- line comment
--[[
	block comment
]]--

-- print hello world
print('Hello World
')

-- 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)