oops!)))))))

Signed-off-by: Alex A. Naanou <alex.nanou@gmail.com>

walk.js

@@ -0,0 +1,222 @@
+/**********************************************************************
+* 
+*
+*
+**********************************************************************/
+((typeof define)[0]=='u'?function(f){module.exports=f(require)}:define)
+(function(require){ var module={} // make module AMD/node compatible...
+/*********************************************************************/
+
+// Walk...
+//
+//	Construct a reusable walker function...
+//	walk(get(..))
+//		-> func(state, ...nodes)
+//
+//	Construct a reusable walker function with set initial state...
+//	walk(get(..), state)
+//		-> func(...nodes)
+//
+//	Walk the nodes...
+//	walk(get(..), state, ...nodes)
+//		-> res
+//
+// The get(..) that walk(..) expects has the following signature:
+//		get(res, node, next(..), down(..), stop(..))
+//			-> res
+//
+//		Queue next nodes to walk...
+//		next(...nodes)
+//			-> undefined
+//			NOTE: this will just queue the nodes and return immediately.
+//			NOTE: the state is passed to the nodes implicitly, the get(..)
+//				handling first node from this list will get the last result
+//				returned by the last get(..) call on this level as it's 
+//				state.
+//
+//		Walk the next set of nodes...
+//		down(state, ...nodes)
+//			-> res
+//			NOTE: this will process all the nodes and then return the 
+//				result.
+//
+//		Stop the walk...
+//		stop()
+//		stop(result)
+//			-> undefined
+//			NOTE: this will break current function execution in a similar 
+//				effect to 'return', i.e. no code in function will be 
+//				executed after stop(..) call...
+//			NOTE: this is done by throwing a special error, this error 
+//				should either not be caught or must be re-thrown, as 
+//				shadowing this exception may have unexpected results...
+//
+//
+// Example:
+//		// sum all the values of a nested array...
+//		var sum = walk(function(res, node, next){
+//			return node instanceof Array ?
+//				// compensate for that next(..) returns undefined...
+//				next(...node) 
+//					|| res
+//				: res + node }, 0)
+//
+//		// depth first walker...
+//		var sumd = walk(function(res, node, next, down, stop){
+//			return node instanceof Array ?
+//				down(res, ...node)
+//				: res + node }, 0)
+//
+//		sum([1, [2], 3, [[4, 5]]]) // -> 15 ...walks the nodes: 1, 3, 2, 4, 5
+//		sumd([1, [2], 3, [[4, 5]]]) // -> 15 ...walks the nodes: 1, 2, 3, 4, 5
+//
+//
+// Example:
+// 		// XXX res/path threading seem unnatural here...
+// 		var __firstZero = walk(function(res, node, next, down, stop){
+// 			var k = node[0]
+// 			var v = node[1]
+// 			var path = res[0]
+// 			return v === 0 ?
+// 					// NOTE: we .slice(1) here to remove the initial null
+// 					//		we added in firstZero(..)...
+// 					stop([ path.slice(1).concat([k]) ])
+// 				: v instanceof Object?
+// 					down(
+// 						[path.concat([k]), null], 
+// 						...Object.entries(v))
+// 				: res }, [[], null])
+// 		var firstZero = function(value){ 
+// 			// NOTE: we are wrapping the input here to make it the same 
+// 			//		format as that of Object.entries(..) items...
+// 			return __firstZero([null, value]).pop() }
+//
+//
+// 		// same as the above but illustrates a different strategy, a bit
+// 		// cleaner but creates a walker every time it's called...
+// 		var firstZero = function(value){
+// 			return walk(
+// 				function(res, node, next, down, stop){
+// 			        var k = node[0]
+// 					var v = node[1]
+// 					var path = res[0]
+// 					return v === 0 ?
+// 							// NOTE: we .slice(1) here to remove the initial null
+// 							//		we added in firstZero(..)...
+// 							stop([ path.slice(1).concat([k]) ])
+// 						: v instanceof Object?
+// 							down(
+// 								[path.concat([k]), null], 
+// 								...Object.entries(v))
+// 						: res }, 
+// 				[[], null], 
+// 				// wrap the input to make it compatible with Object.entries(..) 
+// 				// items...
+// 				[null, value])
+// 					// separate the result from path...
+// 					.pop() }
+//
+//
+// 		firstZero([10, 5, [{x: 1, y: 0}, 4]]) // -> ['2', '0', 'y']
+//
+//
+//
+// NOTE: a walker is returned iff walk(..) is passed a single argument.
+// NOTE: the following two are equivalent:
+// 		walk(get, start, ...nodes) 
+// 		walk(get)(start, ...nodes)
+// NOTE: walk goes breadth first...
+//
+// XXX might be a good idea to move this into it's own module...
+// 		generic-walk might be a good name...
+var walk = function(get, state, ...nodes){
+	// this is used to break out of the recursion...
+	// NOTE: this can leak out but we only care about it's identity thus
+	// 		no damage can be done...
+	var WalkStopException
+	var err_res
+
+	var _step = function(nodes, res){
+		// construct a comfortable env for the user and handle the 
+		// results...
+		var _get = function(node){
+			var next = []
+			res = get(
+				res, 
+				node, 
+				// breadth first step...
+				// 	next(...nodes) -> undefined
+				function(...nodes){ next = nodes },
+				// depth first step...
+				// 	down(state, ..nodes) -> res
+				function(res, ...nodes){ 
+					return _step(nodes, res) },
+				// stop...
+				// 	stop()
+				// 	stop(value)
+				//
+				// NOTE: 'throw' is used to stop all handling, including 
+				// 		the rest of the current level...
+				function(r){
+					err_res = r
+					WalkStopException = new Error('WALK_STOP_EVENT')
+					throw WalkStopException 
+				})
+			return next
+		}
+
+		return nodes.length == 0 ?
+			// no new nodes to walk...
+			res
+			// do the next level...
+			// NOTE: see note below... ( ;) )
+			: _step(nodes
+				.map(_get)
+				.reduce(function(next, e){
+					return e instanceof Array ? 
+						next.concat(e) 
+						: next.push(e) }, []), res) 
+	} 
+	// _step(..) wrapper, handle WalkStopException... 
+	var _walk = function(nodes, res){
+		try{
+			return _step(nodes, res)
+
+		} catch(e){
+			// handle the abort condition...
+			if(e === WalkStopException){
+				return err_res
+			}
+			// something broke...
+			throw e
+		}
+	}
+
+	return (
+		// return a reusable walker...
+		arguments.length == 1 ?
+			// NOTE: this wrapper is here so as to isolate and re-order res 
+			// 		construction and passing it to the next level...
+			// 		this is needed as when we do:
+			// 			step(res, ...nodes.map(_get).reduce(...))
+			// 		res (if immutable) will first get passed by value and 
+			// 		then will get re-assigned in _get(..), thus step(..) will 
+			// 		not see the updated version...
+			// 		This approach simply pushes the pass-by-value of res till 
+			// 		after it gets updated by _get(..).
+			function(res, ...nodes){
+				return _walk(nodes, res) }
+		// reusable walker with a curried initial state... 
+		// NOTE: better keep this immutable or clone this in get(..)
+		: arguments.length == 2 ?
+			function(...nodes){
+				return _walk(nodes, state) }
+		// walk...
+		: _walk(nodes, state))
+}
+
+
+
+
+/**********************************************************************
+* vim:set ts=4 sw=4 :                               */ return module })