xpath1.peg

// Simple Arithmetics Grammar
// ==========================
//
// Accepts expressions like "2 * (3 + 4)" and computes their value.

Filter
  = "//" path:Path { return path }

Expression 
	= Path
    / "@" left:Name _ op:Operator _ right:Value {
    	return {
        	type: "filter",
        	left: left.text,
            right: right.text,
            op: op
        };
    }

Path
	= name:Name "/" path:Path {
    	return [name].concat(path);
    }
    / name:Name "[" _ expr:Expression _ "]" {
    	let slug = { name: name.text, type: "array" };
    	return [slug].concat(expr);
    }
    / Name

Name
  = [A-Za-z][A-Za-z1-9]* {
  	return { type: "name", text: text() } 
  }

Value
  = [^\]]+ {
  	  return { type: "value", text: text() }
    }

Integer "integer"
  = _ [0-9]+ { return parseInt(text(), 10); }

Operator
  = [><=]

_ "whitespace"
  = [ \t\n\r]*