program: structs stmts
       ;

stmts: ( stmt )+
     ;

structs:
  ( "struct" ID maybe_typarms "{" ( field )+ "}" )*
  ;
  
stmt: 
    "var" ID "=" expr ";"
  | "print" expr ";"
  | "{" stmts "}"
  | expr "=" expr ";"
  | "skip" ";"
  | "fun" ID maybe_typarms "(" params ")" ":" type stmt
  | "if" "(" expr ")" stmt ( "else" stmt )?
  | "while" "(" expr ")" stmt
  ;

field: ID ":" type ";" 
     ;

param: ID ":" type
     ;

params: ( param ( "," param )* )? 
      ;

type: 
    "int"
  | "string"
  | "(" types ")" "->" type
  | ID ( "[" types "]" )?
  ;

  
types: ( type ( "," type )* )?
     ;

exprs: ( expr ( "," expr )* )?
     ;

maybe_typarms: ( "[" ID ( "," ID )* "]" )?
             ;

expr: cmp_expr;

cmp_expr: add_expr ( CMP add_expr )?
        ;
  
add_expr: mult_expr (PLUS mult_expr)*
        ;

mult_expr: call_expr (MULT call_expr)*
         ;

call_expr: 
    base_expr ( "(" exprs ")" | "." ID )*
  | ( "new" | "null" ) ID ( "[" types "]" )?
  ;

base_expr:
    ID ( "[" types "]" )?
  | INT
  | STRING
  | "is_null" "(" expr ")"
  | "(" expr ")"
  ;

ID : LETTER ( LETTER | DIGIT )* ;
INT : ( DIGIT )+ ;
LETTER : ( 'a' .. 'z' | 'A' .. 'Z' | '_' ) ;
DIGIT : ( '0' .. '9' ) ;
STRING : '"' (~ '"')* '"' ;

PLUS : ( '+' | '-' );
MULT : ( '*' | '/' | '%' );
CMP : '<' | '>' | "<=" | ">=" | "!=" | "==";

COMMENT : "//" (~ '\n')* '\n'
        | '#' (~ '\n')* '\n'
	;
	
WHITESPACE: (' ' | '\r' | '\n' | '\t')
          ;

// vim: ft=antlr