GoGo.g4

grammar GoGo;

/** The start rule; begin parsing here. */
prog:   func_definition* main;

main:   stat+ ; 

stat:   inc_dec ';'					
    |   expr ';'          			
    |   assignment_stmt ';'			
    |   declaration ';'				
    |   declaration_implicit ';'	
    |   if_stmt 			
    |   while_loop_stmt    							
    |	rtrn_stmt ';'
    |   printf_stmt ';'
    |   print_stmt ';'         		
    ;

expr locals [ TypeSpec *type = nullptr ]
    :   expr mul_div_op expr   		# MulDiv
    |   expr add_sub_op expr   		# AddSub
    |   number                      # numberExpr
    |   variable               		# varExpr
    |   '(' expr ')'				# parens
    |   expr rel_op  expr  			# relative
    |   func_call                   # funcCall
    ;

variable : ID ;

number locals [ TypeSpec *type = nullptr ]
    : INT       #integerConst
    | DOUBLE    #doubleConst
    ;

declaration: VAR ID TYPE '=' (INT | DOUBLE) ; //from GO
declaration_implicit: ID ':='  (INT | DOUBLE) ; //from GO

func_definition: FUNC ID '(' params ')' TYPE? compound_stmt; // from GO
func_call: ID '('func_call_params')';
func_call_params: (expr (',' expr)*)?;

param: '&'? ID TYPE ;
params: (param (',' param)*)? ;

compound_stmt: '{' stat* '}' | stat;

if_stmt: IF expr compound_stmt ((else_if_stmt)* else_stmt)?;

else_stmt: ELSE compound_stmt ;
else_if_stmt: ELSE_IF expr compound_stmt ;

while_loop_stmt: WHILE expr (compound_stmt) ; //From C++

assignment_stmt: ID '=' expr ;

inc_dec: ID inc_dec_op ;

rtrn_stmt: RETURN expr ;

print_stmt: PRINT'('STRING?')' | PRINT'('expr')';
printf_stmt: PRINTF'('STRING(',' expr)*')';



mul_div_op: MUL_OP | DIV_OP;
add_sub_op: ADD_OP | SUB_OP;
rel_op:     EQ_OP | NE_OP | LT_OP | LE_OP | GT_OP | GE_OP; 
inc_dec_op: INC_OP | DEC_OP;


TYPE: 'int' | 'double' | 'void';
VAR: 'var';
FUNC: 'func';
IF: 'if';
ELSE: 'else';
ELSE_IF: 'else if';
WHILE: 'while';
RETURN: 'return';
PRINT: 'print';
PRINTF: 'printf';


MUL_OP: '*';
DIV_OP: '/';

ADD_OP: '+';
SUB_OP: '-';

EQ_OP: '==';
NE_OP: '!=';
LT_OP: '<';
LE_OP: '<=';
GT_OP: '>';
GE_OP: '>=';

INC_OP: '++';
DEC_OP: '--';

DOUBLE:   INT '.' INT;      // match double datatype
ID  :   [a-zA-Z][a-zA-Z0-9]* ;         // match identifiers <label id="code.tour.EXPR.3"/>
INT :   [0-9]+ ;            // match integers
STRING: '"'[a-zA-Z0-9 !@#$%^&*+=:,.\\]+'"';
NEWLINE : '\r'? '\n' -> skip ;        // return newlines to parser (is end-statement signal)
WS  :   ([ \t]+ | ' '+) -> skip ;    // toss out whitespace
COMMENT: ('//' .*? NEWLINE | '/*' .*? '*/') -> skip ; //skip comments