grammar.lark

?program: statement+    //1 o inf statement

// The ?<rule> is important to shape the tree and reduce the 
// number of children for single father if they is useful
?statement: declaration 
          | bool_logic
          | if_stmt
          | for_stmnt
          | "Printf" "(" (expression | bool_logic) ")" -> printf

// Variable declarations and assignment
?declaration: "var" ident_list (DATA_TYPE "=" expression_list | "=" expression_list) -> assignment // Typed or not 
            | ident_list ":=" expression_list -> short_assignment // x := 2 || x,y,z := 2,3,4
            | ident_list ":=" array_type "{" expression_list "}" -> array_assignment // x := [4]int{1,2,3,4}

// Data types
DATA_TYPE: "int" | "string" | "bool"

ident_list      : IDENTIFIER ("," IDENTIFIER)*
expression_list : expression ("," expression)*
array_type      : "[" NUMBER "]" DATA_TYPE

?bool_logic: relation
           | "(" bool_logic ")"
           | bool_logic "&&" bool_logic -> bool_and
           | bool_logic "||" bool_logic -> bool_or
           | "!" bool_logic -> bool_not

?relation: "(" relation ")"
         | expression "<" expression -> less
         | expression ">" expression -> great
         | expression ">=" expression -> great_eq
         | expression "<=" expression -> less_eq
         | expression "==" expression -> equal
         | expression "!=" expression -> not_equal

?expression: "(" expression ")"
           | term
           | addition
           | subtraction

term: "(" term ")"
    | factor
    | "(" addition ")"
    | "(" subtraction ")"
    | multiplication
    | division

factor: NUMBER
      | IDENTIFIER
      | STRING
      | IDENTIFIER "[" expression "]" -> index
      | "Scanf" "(" expression ")" -> scanf

addition        : expression "+" expression
subtraction     : expression "-" expression
multiplication  : term "*" term
division        : term "/" term

block_statement: "{" statement+ "}"

// If Statement
if_stmt: "if" bool_logic block_statement ("else" (if_stmt|block_statement))?

// For Statement
for_stmnt: "for" bool_logic block_statement -> while_loop
         | "for" declaration ";" bool_logic ";" IDENTIFIER "++" block_statement -> for_loop

// String type, enclosed by double quotes (ex. "ciao")
STRING: /".*"/

// Import terminals from common library
%import common.CNAME  -> IDENTIFIER
%import common.NUMBER
%import common.WS

%ignore WS