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Catalog

Name variable

 number Types and operators

 string type

        String and number are converted to each other

  function

table Array

Numeric subscript

table The interface of

  String subscript table

overall situation table——_G

lua True and false in

Branch statement

  Loop statement

for loop

 while loop

  Add ：

---

Name variable

        stay lua in , Assigning a variable is equivalent to naming a variable . Variables that are not known , The value of this variable is equal to nil( amount to c Linguistic NULL).

  Be careful ： stay lua The variable named in the default is a global variable . It can also be used in other files . Function and c Same language

If you want to make a variable local , Add... Before the variable local keyword .

local a = 10

Assignment language can assign multiple variables ：

 number Types and operators

        c There are many built-in types in languages ,int,char,float,double etc. , stay lua in , These types are unified number type .

        lua Languages are also supported 16 Hexadecimal assignment and scientific counting .

          Operator ：lua Basic support c Operators in language , Like addition, subtraction, multiplication and division , power , Move left, move right, etc .

 string type

        Name string variable , Also by assigning a name , Single quotation marks or double quotation marks can be used for strings , also lua Escape character support .

          Use "[[ ]]", It is also a name character , And the string is stored in the original , There will be no escape .

          The connecting symbol of the string ,".."

        String and number are converted to each other

          If tonumber Conversion failure returns nil

          Add a before the string variable '#' You can get the length of the string .

  function

        The format of the function is ：

         

          Return value , If the function does not return , Default return nil, There is a return , Return the corresponding value .

          Function return value , Multiple values can also be returned

table Array

• Numeric subscript

        The use of numerical subscripts and c Arrays in language are similar , It can store numbers , character string , Another one table, Or functions . But starting from 1 It starts with a small mark .

        If you access undefined table Subscript , The value is nil, But you can also assign values .

          have access to '#' To get table Number of elements .

table The interface of

        Plug in the interface insert

          You can also use table Provided insert Interface , To insert elements , Or insert .

          Remove interface remove

        Remove the element at a certain position , And it will return the removed elements .

•   String subscript table

amount to c The structure of language , Can be in the form of an array ( Array of key Must be a string ) perhaps '.' Form access .

Subscripts are represented by strings .

  Insert elements

  Remove elements

Can't use table Of remove Interface , You can set the corresponding value of this string to nil.

  Summarize two ways to remove elements ： Empty or use table Interface remove

1. Numeric subscript , have access to remove And empty

2. String subscript , You can use empty .

• overall situation table——_G

        Global variables are stored in _G overall situation table in .

  Be careful ： Actually table It's also a global variable , His type is a table, So is the name table, It contains elements insert and remove function .

lua True and false in

        lua There is a kind of bool type , Only true and false Two values .

          stay lua There are only false and nil Said the false , Other expressions are true .0 Said really

Be careful ：lua Logical operations in and,or You can directly put back the corresponding value .

        and If it's true , Returns the last true value , If one is true and one is false , Return the corresponding false value , If it's all false , Return the first false value .

        or If it's true , Returns the first true value , If one is true and one is false , Return the corresponding true value , If it's all false , Returns the last false value .

 

Short circuit evaluation can be realized by using this phenomenon .

such as ：

 

Branch statement

        use then Represents the branch statement to be executed later , use end Indicates the end of the branch statement .

  Loop statement

        lua There are three cycles , Namely for loop ,while Circulation and repeat loop .while and repeat Recycling is almost .

• for loop

for Variable definitions , End value , step ( Do not write default is 1) do 

        Code block

end

  Be careful ：

1. for The variable scope defined in this line is only in for In circulation , But in for In the loop, you cannot modify for Circulation is meaningless .

2. And this variable can only be used in for In circulation Visit , It can't be modified . When making modifications , Xiang Dan and Zai for A new local variable is created in the loop .

 3. have access to break keyword , No, continue keyword .

•  while loop

while  Conditions  do
     sentence 
     Change of conditions 
end

          Support break

 

  Add ：

lua String and c Character arrays in languages are much like . have access to string Of char Function constitution lua String , use string Of byte Get a character in the string . And will 0 Save in string , It will not affect the length of the string .