Lua – first steps – part 001.

The name Lua comes from Portuguese meaning moon and is a lightweight, high-level, multi-paradigm programming language designed primarily for embedded use in applications.
Lua was originally designed in 1993 as a language for extending software applications to meet the increasing demand for customization at the time.
Lua is cross-platform since the interpreter of compiled bytecode is written in ANSI C.
Lua has a relatively simple C API to embed into applications.
Let’s start with some information and basic examples, see also this online tool for lua with these examples:

• Lua is case-sensitive: and is a reserved word, example: And and AND are two other different identifiers;
• following words are reserved and we cannot use them as identifiers – variables for example:
  
  Lua

  and break do else elseif end false for function if in local nil not or repeat return then true until while

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  and       break     do        else      elseif     end       false     for       function  if     in        local     nil       not       or     repeat    return    then      true      until     while

• comments on many rows start anywhere with :
  
  Lua

  --[[ this is a comment --]]

  1	--[[ this is a comment --]]

• a single row comment starts with a double hyphen is a punctuation mark (-), start a row commented with — anywhere outside a string, see:
  
  Lua

  -- this is a single row comment

  1	-- this is a single row comment

• Global variables − all variables are considered global unless explicitly declared as local, see:
  
  Lua

  d = 5;

  1

  d = 5;

• Local variables − when the type is specified as local for a variable, its scope is limited with the functions inside their scope, see:
  
  Lua

  local x = 10

  1	local x = 10

• Table fields − this is a special type of variable that can hold anything except nil including functions – can contain functions, but you can assign nil to a table field to delete it.
• These strings denote other tokens:
  
  Lua

  + - * / % ^ # == ~= <= >= < > = ( ) { } [ ] ; : , . .. ...

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  +     -     *     /     %     ^     # ==    ~=    <=    >=    <     >     = (     )     {     }     [     ] ;     :     ,     .     ..    ...

• There are 8 basic types in Lua:
  
  Lua

  nil type of the value nil whose main property is to be different from any other value. It usually represents the absence of a useful value boolean values false and true (both nil and false make a condition false; any other value makes it true) number both integer and floating-point numbers (has internally two distinct representations: integer and float) string arrays of characters (strings may contain any 8-bit character, including embedded zeros) function Lua functions userdata can hold arbitrary C data (corresponds to a block of raw memory) thread independent threads of execution used to implement coroutines table arrays that can hold values of any type except nil

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  nil       type of the value nil whose main property is to be different from any other value.           It usually represents the absence of a useful value boolean   values false and true (both nil and false make a condition false;           any other value makes it true) number    both integer and floating-point numbers (has internally two distinct           representations: integer and float) string    arrays of characters (strings may contain any 8-bit character,           including embedded zeros) function  Lua functions userdata  can hold arbitrary C data (corresponds to a block of raw memory) thread    independent threads of execution used to implement coroutines table     arrays that can hold values of any type except nil

• Relational operators and always result in false or true:
  
  Lua

  == equality ~= negation of equality < smaller than > bigger than <= smaller or equal than >= bigger or equal than

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  ==     equality ~=     negation of equality <      smaller than >      bigger than <=     smaller or equal than >=     bigger or equal than

• Bitwise operators:
  
  Lua

  &: bitwise AND |: bitwise OR ~: bitwise exclusive OR >>: right shift <<: unary bitwise NOT ~: unary bitwise NOT

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  &: bitwise AND |: bitwise OR ~: bitwise exclusive OR >>: right shift <<: unary bitwise NOT ~: unary bitwise NOT

• Statements contains words like: If, For, While, Repeat and Table.
• Concatenation or combine:
  
  word1='-hello' word2=' world' -- result contains '-hello world' result=word1..word2

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  word1='-hello' word2=' world' -- result contains '-hello world' result=word1..word2

The next tutorial will be more complex.