PEG a_pe_grammar (Expression)

 AddOp      <- [-+] ;
 Digit      <- [0123456789] ;
 Expression <- Function / '(' Expression ')' / Factor (MulOp Factor)* ;
 Factor     <- Term (AddOp Term)* ;
 Function   <- Sinus ;
 MulOp      <- [*/] ;
 Number     <- Sign? Digit+ ;
 Sign       <- [-+] ;
 Sinus      <- 'sin(' Expression ')' ;
 Term       <- Number ;

END;
