CODEWITHSUNDEEP
parsingantlrantlr4lexer
MaxThom
MaxThom

Reputation: 1401

ANTLR4 Parser confusion

im trying to user antlr4 for a project and I got an error im not sure I know how to fix. It seems antlr4 is confuse with two parser rules. Here is my lexer/parser :

grammar PARSER;
@header {package VSOP.Parser;}
program                 : code+ ; //statement+ ;

code                    : classHeader | methodHeader | ;
statement               : assign | ifStatement | whileStatement;

classHeader             : 'class' TYPE_IDENTIFIER ('extends' TYPE_IDENTIFIER)? '{' classBody '}';
classBody               : methodHeader* | field*;

methodHeader            : OBJECT_IDENTIFIER '(' (((formal ',')+ (formal)) | (formal)?) ')' ':' varType '{' methodBody '}' ;
methodBody              : statement* ;
formal                  : OBJECT_IDENTIFIER ':' varType ;
field                   : OBJECT_IDENTIFIER ':' varType ('<-' varValue)? ';' ;



assign                  : OBJECT_IDENTIFIER ':' varType ('<-' varValue)? ;

whileStatement          : 'while' condition* 'do' statement* ;

ifStatement             : ifStat elseStat? ; //ifStat elseIfStat* elseStat? ;
ifStat                  : 'if' condition 'then' statement* ;
//elseIfStat              : 'else if' condition 'then' '{' statement* '}' ;
elseStat                : 'else' statement* ;

condition               : comparaiser CONDITIONAL_OPERATOR comparaiser ;
comparaiser             : OBJECT_IDENTIFIER | integer | STRING ;
integer                 : INTEGER_HEX | INTEGER_DEC | INTEGER_BIN ;
varType                 : 'bool' | 'int32' | 'string' | 'unit' | TYPE_IDENTIFIER ;
varValue                : ('true' | 'false' | STRING | integer) ;


   // KEYWORD                 : 'and' | 'class' | 'do' | 'else' | 'extends' | 'false' | 'if' | 'in' | 'isnull' | 'let' | 'new' | 'not' | 'then' | 'true' | 'unit' | 'while' ;
ARITHMETIC_OPERATOR     : '+' | '-' | '*' | '/' | '^' ;
CONDITIONAL_OPERATOR    : '=' | '<' | '<=';
MULTILINE_OPEN_COMMENT  : '(*' ;
MULTILINE_CLOSE_COMMENT : '*)' ;
MULTILINE_COMMENT       : '(*' .*? '*)' ;
INTEGER_BIN             : '0'[bB][0-9a-zA-Z]* ;
INTEGER_HEX             : '0'[xX][0-9a-zA-Z]* ;
INTEGER_DEC             : [0-9][0-9a-zA-Z]* ;

OBJECT_IDENTIFIER       : [a-z][a-zA-Z0-9_]* ;
TYPE_IDENTIFIER         : [A-Z][a-zA-Z0-9_]* ;
STRING                  : '"' ( '\\"' | . )*? ('"' | EOF) ;
SINGLE_LINE_COMMENT     : '//'~[\r\n]* ;
WS                      : [ \r\n\t]+ -> skip;

Using the code below, i get the errors 

line 5:15 mismatched input '(' expecting ':'
line 5:31 mismatched input ',' expecting {'<-', ';'}
line 5:50 mismatched input ',' expecting {'<-', ';'}
line 5:69 mismatched input ')' expecting {'<-', ';'}

The problem is antlr4 confuse methodHeader and field. If I but the var nbOfEngine below the function, I get the function right, but the variable wrong.If i try them separatly, it work as well. I tried changing their order in the parser, without success.

class Plane extends Transport {

    nbOfEngine: int32 ;

    startEngine(gazLevel: int32, readyToStart:bool, foodOnBoard: bool) : bool {

    }
}

Any idea how to fix this ? Thanks !

Upvotes: 0

Views: 97

Answers (2)

MaxThom
MaxThom

Reputation: 1401

I found the issue in the parser. The problem come from classBody.

    classBody               : methodHeader* | field*;

Instead Ive written:

    classHeader             : 'class' TYPE_IDENTIFIER ('extends' TYPE_IDENTIFIER)? '{' classBody* '}';
    classBody               : methodHeader | field;

Upvotes: 0

sepp2k
sepp2k

Reputation: 370092

You define classBody to either be a sequence of field definitions or a sequence of method definitions. You don't allow for it to be a sequence of both.

If you change it to (methodHeader | field)* instead, you'll get a sequence that can contain either.

Upvotes: 2

Related Questions