Simple ParseKit Expression Language grammar

expr.g

@symbols = '!=' '<=' '>=';

@start = expr;
expr = orExpr;

orExpr = andExpr orTerm*;
orTerm = 'or' andExpr;

andExpr = relExpr andTerm*;
andTerm = 'and' relExpr;

relExpr = callExpr (relOp callExpr)*;
relOp = '<' | '>' | '=' | '!=' | '<=' | '>=';

callExpr = primaryExpr ('(' argList ')')?;
argList = Empty | atom (',' atom)*;

primaryExpr = atom | '(' expr ')';
atom = obj | literal;

obj = id member*;
id = Word;
member = '.' id;

literal = QuotedString | Number | bool;
bool = 'yes' | 'no';

// This grammar will parse simple relational boolean expressions like:

foo and bar

(foo or bar) and yes

foo.bar(20) >= 10.0

foo.bar("hello") != "hello"