Renamed some functions, added an internal exception.

defs.js

@@ -4,19 +4,22 @@ const none = Symbol.for('object-stream.none');
 const finalSymbol = Symbol.for('object-stream.final');
 const manySymbol = Symbol.for('object-stream.many');
 
-const final = value => ({[finalSymbol]: value});
+const finalValue = value => ({[finalSymbol]: value});
 const many = values => ({[manySymbol]: values});
 
-const isFinal = o => o && typeof o == 'object' && finalSymbol in o;
+const isFinalValue = o => o && typeof o == 'object' && finalSymbol in o;
 const isMany = o => o && typeof o == 'object' && manySymbol in o;
 
 const getFinalValue = o => o[finalSymbol];
 const getManyValues = o => o[manySymbol];
 
+class Stop {}
+
 module.exports.none = none;
-module.exports.final = final;
-module.exports.isFinal = isFinal;
+module.exports.finalValue = finalValue;
+module.exports.isFinalValue = isFinalValue;
 module.exports.getFinalValue = getFinalValue;
 module.exports.many = many;
 module.exports.isMany = isMany;
 module.exports.getManyValues = getManyValues;
+module.exports.Stop = Stop;