1 Judgment statement

The judgment block consists of if,elseif,else Keywords make up , also With end Keyword end . The result of a conditional expression can be any value .Lua Lieutenant general false and nil Be false , All other values are treated as true （0 And empty strings are also treated as true ）.

--  Definition 1
if  expression  then
	 Sentence block 
end

--  Definition 2
if  expression  then
	 Sentence block 
else
   Sentence block 
end

--  Definition 3
if  expression  then
	 Sentence block 
elseif  expression  then
   Sentence block 
elseif  expression  then
   Sentence block 
...
else
   Sentence block 
end

Definition 1 Demonstration examples are as follows ：

a = 10

if a < 20 then print("ok") end

if nil then print("I am nil") end

if 0 then print("I am 0") end

function func(b)
	if a == b then
		print("equals")
	end
end

func(10)

--  The output is as follows 
ok
I am 0
equals

Definition 2 Demonstration examples are as follows ：

name = "chenpi"

function func(myname)
	if name == myname then
		print("equals")
	else
		print("not equals")
	end
end

func("chenpiok")

--  The output is as follows 
not equals

Definition 3 Demonstration examples are as follows ：

function func(age)
	if age ==10 then
		print("1")
	elseif age == 20 then
		print("2")
	else
	  print("3")
	end
end

func(20) -- 2

2 Loop statement

2.1 while…do

while  The loop condition  do
	 The loop body 
end

--  Example , Output 1-5 Five numbers 
local i = 1
while i <= 5 do
  print(i)
	i = i + 1
end

2.2 for…do

for  Variable  =  Initial value ,  Termination value ,  step  do
	 The loop body 
end

--  Example , Output 1-5 Five numbers 
for i = 1, 5, 1 do
    print(i)
end

for i = 1, 5 do  --  The step size can be omitted , The default is 1
    print(i)
end

--  Output 5-1
for i = 5, 1, -1 do
    print(i)
end

We need to pay attention to , Initial value , Termination value , Every step will be executed only once , So even if you're in the loop , It's no use changing their values .

--  The following example still only outputs 1-5 Five numbers 
local x = 5
local y = 1
for i = 1, x, y do
    print(i)
    x = 10
    y = 3
end

2.3 repeat…until

repeat
	 The loop body 
until  The loop condition 

--  Example , Output 1-5 Five numbers 
local i = 1
repeat
    print(i)
	i = i + 1
until i > 5

2.4 for…in…do

for  Variable list  in  iterator  do
	 The loop body 
end

t = {
    "a", "b", "c"}
for k,v in pairs(t) do
	print(k..":"..v)
end

--  The output is as follows 
1:a
2:b
3:c

We can customize an iterator .

--  Define iterator 
function mypairs(t)
	return myfunc, t, 0 --  Return iteration function , The set to be traversed , Control variables . The set to be traversed , The control variable will be passed into the iterative function 
end

function myfunc(t, i)
    i = i + 1
    local v = t[i]
    if v then
        return i, v
    end
    return nil, nil
end

t = {
    "a", "b", "c"}
for k,v in mypairs(t) do
	print(k..":"..v)
end

--  The output is as follows 
1:a
2:b
3:c

2.5 break

break Can jump out of the loop .

for i = 1, 5, 1 do
    print(i)
    if i == 3 then
    	break
    end
end

---

This sharing is over ~~

I am a Dried tangerine or orange peel , One on the Internet Coding Of ITer. If you think the article will help you , give the thumbs-up 、 Collection 、 Focus on 、 Comment on , Your support is the biggest motivation for my creation ！