Lua advanced

Preface

        Learn to query documents ： Official document link ——Lua 5.3 Reference manual - Catalog

Multiple file calls

        Use require keyword ：

• Run the specified file name .
• No extension at the end .
• For directory level '.' Separate .

• It will only run once .
• The return value of the call will be returned .

• The called file is from package.path Find... In the path .

commonly require It is used to call external library files , Generally, you don't need to call many times .

  iterator

The function is to traverse table All the values of .

commonly table Iteration ：

  There are two kinds of iterators ：

• ipairs

        ipairs Apply to With numbers and continuous Subscript table.

          If you encounter discontinuous numerical subscripts table, encounter table Numerical subscript not in , Until we return nil, here ,ipairs Will stop traversing .

•  pairs

Applicable to string subscripts and discontinuous numerical subscripts .

 pairs The internal call is next function .

next() function , Will return the incoming table The next value of the value ,pairs The obtained value is recorded in .

  use next You can also quickly judge a table Is it empty .

string

lua in string Characteristics

• Storage structure of string .

         stay lua The storage structure of string in is equivalent to C++ Medium vector<char> In the form of . One character, one character is saved in the array . What is actually saved is the bytecode of the character .

•   You can save any character string , The scope is 0x00~0xff, Include invisible characters . What is special is 0x00, stay c The language is in the form of '0' Character ending , The following characters are lost . stay lua Not in the , Because it records the number of characters ,

•   The string has a sequence number , Save positive sequence number and negative sequence number .

Positive sequence number , The starting position 1 Start , After that, add . Negative sequence number , At the end of -1 Start , Decrease in front .

 string The interface of

• string.byte (s [, i [, j]])

  Return character  s[i], s[i+1], ...　,s[j]  Internal digital code of . i  The default value of is 1 ; j  The default value of is  i.

•  string.char (···)
  Receive zero or more integers . Returns a string of the same length as the number of parameters . The internal code value of each character is equal to the corresponding parameter value .

•  string.format (formatstring, ···) Returns the formatted version of an indefinite number of parameters , Format the string as the first parameter （ Must be a string ）. and c Linguistic printf It doesn't make any difference .

•  string.lower (s)
  Receive a string , Turn all uppercase characters into lowercase and return a copy . Other strings will not change . The definition of upper case characters depends on the current locale .

•  string.pack (fmt, v1, v2, ···)

  Return a package （ That is, serialize in binary form ） v1, v2  Equivalent binary string . character string  fmt  In packaging format （ See  §6.4.2）.