introduction to lua
print("hello world")
comment
-- one line
--[[
multiple lines
--]]
global variable, value is treated as global by default, only you use “local” to define it. if you awnt to delete it, just set it as nil.
Lua data type：nil、boolean、number、string、userdata、function、thread、table. Logic operations: and, or, not
print(type("hello world"))
-- string
print(type(true))
-- boolean
string
string1 = "hello world"
string2 = 'hello world'
string3 = [[
hello world
]]
– string append
print("a"…'b')
– string length #
print(#string2)
string.len("abc")
– string to upper
string.upper(argument)
– string to lower
string.lower(argument)
– string replace
string.gsub(mainString,findString,replaceString,num)
string.gsub("aaaa","a","z",3)
– return zzza, 3
– find the index, 1 as the begin point
string.find("Hello Lua user", "Lua", 1)
– reverse the string
string.reverse("lua")
– string copy
string.rep("abc", 2)
table
local tbl2 = {"apple", "pear", "orange", "grape"}
– table contact
fruits = {"banana","orange","apple"}
print(table.concat(fruits))
– return bananaorangeapple
print(table.concat(fruits,", "))
– return banana, orange, apple
print(table.concat(fruits,", ", 2,3))
– return orange, apple
– remove
table.remove(fruits, pos)
– insert
table.insert(fruits, 2, "mongo")
–sort
table.sort(fruits)
function
function factorial1(n)
if n == 0 then
return 1
else
return n * factorial1(n - 1)
end
end
print(factorial1(5))
factorial2 = factorial1
print(factorial2(5))
– it can also return multiple values
s, e = string.find("www.runoob.com", "runoob")
– return 5 10
user data: user can define the data type and value at any style
assignment
t.n = t.n + 1
a, b = 10, 2*x <--> a=10; b=2*x
a[i], a[j] = a[j], a[i] -- swap 'a[i]' for 'a[j]'
a, b, c = 0, 1
print(a,b,c) --> 0 1 nil
a, b = a+1, b+1, b+2 -- value of b+2 is ignored
print(a,b) --> 1 2
index
t[i]
t.i
loop
-- false and nil are false, true and non-nil are true, so 0 is false
if(0)
then
print("0 is true")
end
if (condition1)
then
do sth1
elseif (condition2)
then
do sth2
else
do sth3
end
while( true )
do
print("loop forever")
end
for i=1,f(x) do
print(i)
end
for i=10,1,-1 do
print(i)
end
days = {"Suanday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"}
for i, v in ipairs(days) do
print(v)
end
repeat
statements
until( condition )
– can use break
module
module={}
module.constant = "value"
function module.func()
io.write("a public function")
end
-- load a module
require "module"
IO
-- only read
file = io.open("test.lua", "r")
io.input(file)
io.close(file)
io.write("-- test.lua 文件末尾注释")
coroutine
-- use producer and consumer as the example
local newProductor
function productor()
local i = 0
while true do
i = i + 1
send(i) – send the products to consumers
end
end
function consumer()
while true do
local i = receive() – get the products from the productor
print(i)
end
end
function receive()
local status, value = coroutine.resume(newProductor)
return value
end
function send(x)
coroutine.yield(x) – x is the value, coroutine
end
– start
newProductor = coroutine.create(productor)
consumer()
