fhirpathmin.g4

grammar fhirpathmin;

expression
        : expression '.' expression        #chain
        | expression '[' int ']'           #index
        | FIRST                            #first
        | WHERE predicate ')'         #where
        | element                          #term
        ;

predicate : expression eqop   (expression | string)  #eqpred
          | expression compop (expression | number)  #mathpred
          | predicate boolop predicate               #boolpred
          | '(' predicate ')'                        #predicateGroup
          ;

eqop:   ('=' | '!=');
compop: ('<=' | '<' | '>' | '>=' | '=' );
boolop: ('or' | 'and');


element: NAME;
string: STRING;
number: NUMBER;
int: INT;

NAME    : [_a-zA-Z][_a-zA-Z0-9]* ;
WHERE   : 'where(';
FIRST   : 'first()';
INT     : [0-9]+ ;
NUMBER  : [0-9]+('.' [0-9]+)? ;
STRING  : '\'' ~('\'')* '\'' ;
WS  :   [ \t\n\r]+ -> skip ;