Grammar Reference¶

The FOOL grammar is defined in compiler/FOOL.g4 using ANTLR 4.

Program Structure¶

A FOOL program is either a single expression or a let … in block that introduces declarations before the main expression.

prog : progbody EOF ;

progbody : LET ( cldec+ dec* | dec+ ) IN exp SEMIC   # letInProg
         | exp SEMIC                                  # noDecProg
         ;

Class Declarations¶

cldec : CLASS ID (EXTENDS ID)?
            LPAR (ID COLON type (COMMA ID COLON type)* )? RPAR
            CLPAR
                 methdec*
            CRPAR ;

A class can optionally extend another class. Its body contains field declarations (in the parameter list) and method declarations.

Method & Function Declarations¶

methdec : FUN ID COLON type
              LPAR (ID COLON type (COMMA ID COLON type)* )? RPAR
                   (LET dec+ IN)? exp
              SEMIC ;

dec : VAR ID COLON type ASS exp SEMIC   # vardec
    | FUN ID COLON type
          LPAR (ID COLON type (COMMA ID COLON type)* )? RPAR
               (LET dec+ IN)? exp
          SEMIC                         # fundec
    ;

Expressions¶

exp : exp (TIMES | DIV) exp          # timesDiv
    | exp (PLUS | MINUS) exp         # plusMinus
    | exp (EQ | GE | LE) exp         # comp
    | exp (AND | OR) exp             # andOr
    | NOT exp                        # not
    | LPAR exp RPAR                  # pars
    | MINUS? NUM                     # integer
    | TRUE                           # true
    | FALSE                          # false
    | NULL                           # null
    | NEW ID LPAR (exp (COMMA exp)* )? RPAR                    # new
    | IF exp THEN CLPAR exp CRPAR ELSE CLPAR exp CRPAR         # if
    | PRINT LPAR exp RPAR                                      # print
    | ID                                                       # id
    | ID LPAR (exp (COMMA exp)* )? RPAR                        # call
    | ID DOT ID LPAR (exp (COMMA exp)* )? RPAR                 # dotCall
    ;

Types¶

type : INT    # intType
     | BOOL   # boolType
     | ID     # idType   (class reference)
     ;

Keywords & Operators¶

Token	Value
INT	int
BOOL	bool
TRUE / FALSE	true / false
NULL	null
IF / THEN / ELSE	if / then / else
LET / IN	let / in
VAR	var
FUN	fun
CLASS / EXTENDS	class / extends
NEW	new
PRINT	print
Arithmetic	+ - * /
Comparison	== >= <=
Logical	\|\| && !