lua learning record

(Reference: https: //www.runoob.com/lua/lua-tutorial.html)

First, the basic

1 Print

print("Hello")
print(123)

operation result:

Hello
123

2 comments

- Line Mark, single-line comment 
- [[ 
multiline comment 
MANY 
Line 
Mark 
]] -

 

3, variable assignment

- default global variables 
Print (B) 
B = 10 
Print (B) 

HTML = [[ 
. 1A 
2BC 
3DEF 
4G 
QWE 
]] 
Print (HTML)

 

operation result:

nil
10
1a
2bc
3def
4g
qwe

4, and the connection string number plus

= A ' . 1 ' 
B = 2 
- + are by digital processing 
Print (A + B)
 - This is the string concatenation 
Print (A .. B)

 

operation result:

3.0
12

 5, arrays, lists

--tab used either when the array, may be used as a map
- Lua subscript 1 starting from

tab1 = {"a","b","c"}
for k in pairs(tab1) do
print(k .. ":" .. tab1[k])
end

 

operation result:

1:a
2:b
3:c

6, circulation

- the initial value, the cutoff value, the step size (default. 1) 
for I = 10 , . 1 , - 2  do 
Print (I)
 End 

- except pairs, ipairs iteration may be 
A = { " One " , " TWO " , " Three " }
 - Lua script "on line", plus the ";" on the semicolon 
for I, V in  ipairs (A) do  Print (I, V); Print (I .. " : " . . v) End

 

operation result:

10
8
6
4
2
1 one
1:one
2 two
2:two
3 three
3:three

7, if determined

--0是true
if(0) then print("0 is true") end

num = 100
--if else的使用
if(num<20) then print("num < 20") else print("num >= 20") end
print("num value is :", num)
--多重判断
-- if then elseif then else end

 

operation result:

0 is true
num >= 20
num value is : 100

8, string search

--返回值startIndex,endIndex,start 1
s,e=string.find("www.runoob.com", "run")
print(s,e)

 

operation result:

5       7

Second, the function call

1, defined functions, and calls

function max(num1, num2)
    if(num1 > num2) then
        result = num1
    else
    result = num2
    end
    return result
end

print("the max is:", max(10, 4))
print("the max is:", max(5,6))

 

operation result:

the max is: 10
the max is: 6

2, as a function of transmission parameters

myprint = function(param)
    print("This is print function - ##", param, "##")
end

function add(num1, num2, funcPrint)
    result = num1 + num2
    funcPrint(result)
end
myprint(100)
add(2,5,myprint)

 

operation result:

This is print function - ## 100 ##
This is print function - ## 7 ##

3, variable length parameters passed

--not fix args num
function add_many(...)
    local s = 0
    for i,v in ipairs{...} do
        s = s+v
    end
    return s
end
print(add_many(1,2,3,4,5))

 

operation result:

15

4, the length of the variable length parameter

a, by obtaining a length #arg

b, the length by obtaining select ( "#", ...)

function average(...)
    local res = 0
    local arg = {...}
    for i,v in ipairs(arg) do
        res = res + v
    end
    --#arg or select("#", ...)
    print("arg num is:" .. #arg .. ".")
    return res/#arg
end
print(average(1,2,3,4,5))

 

operation result:

arg num is:5.
3.0