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https://github.com/flynx/diff.js.git
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added stop(..) to walk(..) + examples...
Signed-off-by: Alex A. Naanou <alex.nanou@gmail.com>
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diff.js
205
diff.js
@ -263,17 +263,23 @@ var proxy = function(path, func){
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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//
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// Construct a reusable walker function...
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// walk(get(..))
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// -> func(start, ...nodes)
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// -> func(state, ...nodes)
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//
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// Construct a reusable walker function with set initial state...
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// walk(get(..), state)
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// -> func(...nodes)
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//
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// Walk the nodes...
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// walk(get(..), start, ...nodes)
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// walk(get(..), state, ...nodes)
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// -> res
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//
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// The get(..) that walk(..) expects has the following signature:
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// get(res, node, next(..), down(..))
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// get(res, node, next(..), down(..), stop(..))
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// -> res
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//
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// Queue next nodes to walk...
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@ -286,41 +292,90 @@ var proxy = function(path, func){
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// state.
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//
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// Walk the next set of nodes...
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// down(start, ...nodes)
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// down(state, ...nodes)
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// -> res
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// NOTE: this will process all the nodes and then return the
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// result.
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//
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// Stop the walk...
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// stop()
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// stop(result)
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// -> undefined
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// NOTE: this will break current function execution in a similar
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// effect to 'return', i.e. no code in function will be
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// executed after stop(..) call...
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// NOTE: this is done by throwing a special error, this error
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// should either not be caught or must be re-thrown, as
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// shadowing this exception may have unexpected results...
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//
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//
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// Example:
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// // sum all the values of a nested array...
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// var sum = walk(function(res, node, next){
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// // go into arrays...
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// if(node instanceof Array){
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// next(...node)
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//
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// // sum the values...
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// } else {
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// console.log(node)
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// res += node
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// }
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// return res
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// })
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// return node instanceof Array ?
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// // compensate for that next(..) returns undefined...
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// next(...node)
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// || res
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// : res + node }, 0)
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//
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// // depth first walker...
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// var sumd = walk(function(res, node, next, down){
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// if(node instanceof Array){
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// res = down(res, ...node)
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// var sumd = walk(function(res, node, next, down, stop){
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// return node instanceof Array ?
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// down(res, ...node)
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// : res + node }, 0)
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//
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// } else {
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// console.log(node)
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// res += node
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// }
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// return res
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// })
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// sum([1, [2], 3, [[4, 5]]]) // -> 15 ...walks the nodes: 1, 3, 2, 4, 5
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// sumd([1, [2], 3, [[4, 5]]]) // -> 15 ...walks the nodes: 1, 2, 3, 4, 5
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//
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//
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// Example:
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// // XXX res/path threading seem unnatural here...
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// var __firstZero = walk(function(res, node, next, down, stop){
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// var k = node[0]
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// var v = node[1]
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// var path = res[0]
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// return v === 0 ?
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// // NOTE: we .slice(1) here to remove the initial null
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// // we added in firstZero(..)...
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// stop([ path.slice(1).concat([k]) ])
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// : v instanceof Object?
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// down(
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// [path.concat([k]), null],
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// ...Object.entries(v))
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// : res }, [[], null])
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// var firstZero = function(value){
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// // NOTE: we are wrapping the input here to make it the same
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// // format as that of Object.entries(..) items...
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// return __firstZero([null, value]).pop() }
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//
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//
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// // same as the above but illustrates a different strategy, a bit
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// // cleaner but creates a walker every time it's called...
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// var firstZero = function(value){
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// return walk(
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// function(res, node, next, down, stop){
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// var k = node[0]
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// var v = node[1]
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// var path = res[0]
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// return v === 0 ?
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// // NOTE: we .slice(1) here to remove the initial null
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// // we added in firstZero(..)...
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// stop([ path.slice(1).concat([k]) ])
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// : v instanceof Object?
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// down(
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// [path.concat([k]), null],
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// ...Object.entries(v))
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// : res },
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// [[], null],
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// // wrap the input to make it compatible with Object.entries(..)
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// // items...
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// [null, value])
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// // separate the result from path...
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// .pop() }
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//
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//
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// firstZero([10, 5, [{x: 1, y: 0}, 4]]) // -> ['2', '0', 'y']
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//
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// sum([1, [2], 3, [[4, 5]]]) // -> 15 and log 1, 3, 2, 4, 5
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// sumd([1, [2], 3, [[4, 5]]]) // -> 15 and log 1, 2, 3, 4, 5
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//
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//
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// NOTE: a walker is returned iff walk(..) is passed a single argument.
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@ -329,60 +384,92 @@ var proxy = function(path, func){
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// walk(get)(start, ...nodes)
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// NOTE: walk goes breadth first...
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//
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var walk = function(get, state, ...args){
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var _step = function(args, res){
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// XXX might be a good idea to move this into it's own module...
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// generic-walk might be a good name...
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var walk = function(get, state, ...nodes){
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// this is used to break out of the recursion...
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// NOTE: this can leak out but we only care about it's identity thus
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// no damage can be done...
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var WalkStopException
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var err_res
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var _step = function(nodes, res){
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// construct a comfortable env for the user and handle the
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// results...
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var _get = function(node){
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var next = []
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res = get(res, node,
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res = get(
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res,
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node,
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// breadth first step...
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// next(...nodes)
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// -> undefined
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// NOTE: this is different to down(..) in that this will
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// return immediately and no result is known at time
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// of call thus undefined is returned...
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// NOTE: this is different to down(..) in that the user
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// indirectly gives this the state by returning it
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// from the last get(..) called per level.
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// next(...nodes) -> undefined
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function(...nodes){ next = nodes },
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// depth first step...
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// down(state, ..nodes)
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// -> res
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// NOTE: this is different to next as the user has control
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// over what value to start with and will get the
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// result they can handle...
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// down(state, ..nodes) -> res
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function(res, ...nodes){
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return _step(nodes, res) })
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return _step(nodes, res) },
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// stop...
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// stop()
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// stop(value)
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//
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// NOTE: 'throw' is used to stop all handling, including
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// the rest of the current level...
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function(r){
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err_res = r
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WalkStopException = new Error('WALK_STOP_EVENT')
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throw WalkStopException
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})
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return next
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}
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return args.length == 0 ?
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return nodes.length == 0 ?
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// no new nodes to walk...
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res
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// do the next level...
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// NOTE: see note below... ( ;) )
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: _step(args
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: _step(nodes
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.map(_get)
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.reduce(function(next, e){
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return e instanceof Array ?
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next.concat(e)
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: next.push(e) }, []), res) }
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: next.push(e) }, []), res)
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}
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// call _step(..) and handle WalkStopException...
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var _walk = function(nodes, res){
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try{
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return _step(nodes, res)
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return arguments.length == 1 ?
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} catch(e){
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// handle the abort condition...
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if(e === WalkStopException){
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return err_res
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}
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// something broke...
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throw e
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}
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}
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return (
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// return a reusable walker...
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// NOTE: this wrapper is here so as to isolate and re-order res
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// construction and passing it to the next level...
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// this is needed as when we do:
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// step(res, ...args.map(_get).reduce(...))
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// res (if immutable) will first get passed by value and
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// then will get re-assigned in _get(..), thus step(..) will
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// not see the updated version...
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// This approach simply pushes the pass-by-value of res till
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// after it gets updated by _get(..).
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function(res, ...args){
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return _step(args, res) }
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arguments.length == 1 ?
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// NOTE: this wrapper is here so as to isolate and re-order res
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// construction and passing it to the next level...
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// this is needed as when we do:
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// step(res, ...nodes.map(_get).reduce(...))
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// res (if immutable) will first get passed by value and
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// then will get re-assigned in _get(..), thus step(..) will
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// not see the updated version...
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// This approach simply pushes the pass-by-value of res till
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// after it gets updated by _get(..).
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function(res, ...nodes){
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return _walk(nodes, res) }
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// reusable walker with a curried initial state...
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// NOTE: better keep this immutable or clone this in get(..)
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: arguments.length == 2 ?
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function(...nodes){
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return _walk(nodes, state) }
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// walk...
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: _step(args, res)
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: _walk(nodes, state))
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}
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