// Copyright 2007 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
/**
* @fileoverview Python style iteration utilities.
* @author arv@google.com (Erik Arvidsson)
*/
goog.provide('goog.iter');
goog.provide('goog.iter.Iterable');
goog.provide('goog.iter.Iterator');
goog.provide('goog.iter.StopIteration');
goog.require('goog.array');
goog.require('goog.asserts');
goog.require('goog.functions');
goog.require('goog.math');
/**
* @typedef {goog.iter.Iterator|{length:number}|{__iterator__}}
*/
goog.iter.Iterable;
/**
* Singleton Error object that is used to terminate iterations.
* @const {!Error}
*/
goog.iter.StopIteration = ('StopIteration' in goog.global) ?
// For script engines that support legacy iterators.
goog.global['StopIteration'] :
{message: 'StopIteration', stack: ''};
/**
* Class/interface for iterators. An iterator needs to implement a {@code next}
* method and it needs to throw a {@code goog.iter.StopIteration} when the
* iteration passes beyond the end. Iterators have no {@code hasNext} method.
* It is recommended to always use the helper functions to iterate over the
* iterator or in case you are only targeting JavaScript 1.7 for in loops.
* @constructor
* @template VALUE
*/
goog.iter.Iterator = function() {};
/**
* Returns the next value of the iteration. This will throw the object
* {@see goog.iter#StopIteration} when the iteration passes the end.
* @return {VALUE} Any object or value.
*/
goog.iter.Iterator.prototype.next = function() {
throw goog.iter.StopIteration;
};
/**
* Returns the {@code Iterator} object itself. This is used to implement
* the iterator protocol in JavaScript 1.7
* @param {boolean=} opt_keys Whether to return the keys or values. Default is
* to only return the values. This is being used by the for-in loop (true)
* and the for-each-in loop (false). Even though the param gives a hint
* about what the iterator will return there is no guarantee that it will
* return the keys when true is passed.
* @return {!goog.iter.Iterator<VALUE>} The object itself.
*/
goog.iter.Iterator.prototype.__iterator__ = function(opt_keys) {
return this;
};
/**
* Returns an iterator that knows how to iterate over the values in the object.
* @param {goog.iter.Iterator<VALUE>|goog.iter.Iterable} iterable If the
* object is an iterator it will be returned as is. If the object has an
* {@code __iterator__} method that will be called to get the value
* iterator. If the object is an array-like object we create an iterator
* for that.
* @return {!goog.iter.Iterator<VALUE>} An iterator that knows how to iterate
* over the values in {@code iterable}.
* @template VALUE
*/
goog.iter.toIterator = function(iterable) {
if (iterable instanceof goog.iter.Iterator) {
return iterable;
}
if (typeof iterable.__iterator__ == 'function') {
return iterable.__iterator__(false);
}
if (goog.isArrayLike(iterable)) {
var i = 0;
var newIter = new goog.iter.Iterator;
newIter.next = function() {
while (true) {
if (i >= iterable.length) {
throw goog.iter.StopIteration;
}
// Don't include deleted elements.
if (!(i in iterable)) {
i++;
continue;
}
return iterable[i++];
}
};
return newIter;
}
// TODO(arv): Should we fall back on goog.structs.getValues()?
throw Error('Not implemented');
};
/**
* Calls a function for each element in the iterator with the element of the
* iterator passed as argument.
*
* @param {goog.iter.Iterator<VALUE>|goog.iter.Iterable} iterable The iterator
* to iterate over. If the iterable is an object {@code toIterator} will be
* called on it.
* @param {function(this:THIS,VALUE,?,!goog.iter.Iterator<VALUE>)} f
* The function to call for every element. This function takes 3 arguments
* (the element, undefined, and the iterator) and the return value is
* irrelevant. The reason for passing undefined as the second argument is
* so that the same function can be used in {@see goog.array#forEach} as
* well as others. The third parameter is of type "number" for
* arraylike objects, undefined, otherwise.
* @param {THIS=} opt_obj The object to be used as the value of 'this' within
* {@code f}.
* @template THIS, VALUE
*/
goog.iter.forEach = function(iterable, f, opt_obj) {
if (goog.isArrayLike(iterable)) {
try {
// NOTES: this passes the index number to the second parameter
// of the callback contrary to the documentation above.
goog.array.forEach(
/** @type {IArrayLike<?>} */ (iterable), f, opt_obj);
} catch (ex) {
if (ex !== goog.iter.StopIteration) {
throw ex;
}
}
} else {
iterable = goog.iter.toIterator(iterable);
try {
while (true) {
f.call(opt_obj, iterable.next(), undefined, iterable);
}
} catch (ex) {
if (ex !== goog.iter.StopIteration) {
throw ex;
}
}
}
};
/**
* Calls a function for every element in the iterator, and if the function
* returns true adds the element to a new iterator.
*
* @param {goog.iter.Iterator<VALUE>|goog.iter.Iterable} iterable The iterator
* to iterate over.
* @param {
* function(this:THIS,VALUE,undefined,!goog.iter.Iterator<VALUE>):boolean} f
* The function to call for every element. This function takes 3 arguments
* (the element, undefined, and the iterator) and should return a boolean.
* If the return value is true the element will be included in the returned
* iterator. If it is false the element is not included.
* @param {THIS=} opt_obj The object to be used as the value of 'this' within
* {@code f}.
* @return {!goog.iter.Iterator<VALUE>} A new iterator in which only elements
* that passed the test are present.
* @template THIS, VALUE
*/
goog.iter.filter = function(iterable, f, opt_obj) {
var iterator = goog.iter.toIterator(iterable);
var newIter = new goog.iter.Iterator;
newIter.next = function() {
while (true) {
var val = iterator.next();
if (f.call(opt_obj, val, undefined, iterator)) {
return val;
}
}
};
return newIter;
};
/**
* Calls a function for every element in the iterator, and if the function
* returns false adds the element to a new iterator.
*
* @param {goog.iter.Iterator<VALUE>|goog.iter.Iterable} iterable The iterator
* to iterate over.
* @param {
* function(this:THIS,VALUE,undefined,!goog.iter.Iterator<VALUE>):boolean} f
* The function to call for every element. This function takes 3 arguments
* (the element, undefined, and the iterator) and should return a boolean.
* If the return value is false the element will be included in the returned
* iterator. If it is true the element is not included.
* @param {THIS=} opt_obj The object to be used as the value of 'this' within
* {@code f}.
* @return {!goog.iter.Iterator<VALUE>} A new iterator in which only elements
* that did not pass the test are present.
* @template THIS, VALUE
*/
goog.iter.filterFalse = function(iterable, f, opt_obj) {
return goog.iter.filter(iterable, goog.functions.not(f), opt_obj);
};
/**
* Creates a new iterator that returns the values in a range. This function
* can take 1, 2 or 3 arguments:
* <pre>
* range(5) same as range(0, 5, 1)
* range(2, 5) same as range(2, 5, 1)
* </pre>
*
* @param {number} startOrStop The stop value if only one argument is provided.
* The start value if 2 or more arguments are provided. If only one
* argument is used the start value is 0.
* @param {number=} opt_stop The stop value. If left out then the first
* argument is used as the stop value.
* @param {number=} opt_step The number to increment with between each call to
* next. This can be negative.
* @return {!goog.iter.Iterator<number>} A new iterator that returns the values
* in the range.
*/
goog.iter.range = function(startOrStop, opt_stop, opt_step) {
var start = 0;
var stop = startOrStop;
var step = opt_step || 1;
if (arguments.length > 1) {
start = startOrStop;
stop = opt_stop;
}
if (step == 0) {
throw Error('Range step argument must not be zero');
}
var newIter = new goog.iter.Iterator;
newIter.next = function() {
if (step > 0 && start >= stop || step < 0 && start <= stop) {
throw goog.iter.StopIteration;
}
var rv = start;
start += step;
return rv;
};
return newIter;
};
/**
* Joins the values in a iterator with a delimiter.
* @param {goog.iter.Iterator<VALUE>|goog.iter.Iterable} iterable The iterator
* to get the values from.
* @param {string} deliminator The text to put between the values.
* @return {string} The joined value string.
* @template VALUE
*/
goog.iter.join = function(iterable, deliminator) {
return goog.iter.toArray(iterable).join(deliminator);
};
/**
* For every element in the iterator call a function and return a new iterator
* with that value.
*
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} iterable The
* iterator to iterate over.
* @param {
* function(this:THIS,VALUE,undefined,!goog.iter.Iterator<VALUE>):RESULT} f
* The function to call for every element. This function takes 3 arguments
* (the element, undefined, and the iterator) and should return a new value.
* @param {THIS=} opt_obj The object to be used as the value of 'this' within
* {@code f}.
* @return {!goog.iter.Iterator<RESULT>} A new iterator that returns the
* results of applying the function to each element in the original
* iterator.
* @template THIS, VALUE, RESULT
*/
goog.iter.map = function(iterable, f, opt_obj) {
var iterator = goog.iter.toIterator(iterable);
var newIter = new goog.iter.Iterator;
newIter.next = function() {
var val = iterator.next();
return f.call(opt_obj, val, undefined, iterator);
};
return newIter;
};
/**
* Passes every element of an iterator into a function and accumulates the
* result.
*
* @param {goog.iter.Iterator<VALUE>|goog.iter.Iterable} iterable The iterator
* to iterate over.
* @param {function(this:THIS,VALUE,VALUE):VALUE} f The function to call for
* every element. This function takes 2 arguments (the function's previous
* result or the initial value, and the value of the current element).
* function(previousValue, currentElement) : newValue.
* @param {VALUE} val The initial value to pass into the function on the first
* call.
* @param {THIS=} opt_obj The object to be used as the value of 'this' within
* f.
* @return {VALUE} Result of evaluating f repeatedly across the values of
* the iterator.
* @template THIS, VALUE
*/
goog.iter.reduce = function(iterable, f, val, opt_obj) {
var rval = val;
goog.iter.forEach(
iterable, function(val) { rval = f.call(opt_obj, rval, val); });
return rval;
};
/**
* Goes through the values in the iterator. Calls f for each of these, and if
* any of them returns true, this returns true (without checking the rest). If
* all return false this will return false.
*
* @param {goog.iter.Iterator<VALUE>|goog.iter.Iterable} iterable The iterator
* object.
* @param {
* function(this:THIS,VALUE,undefined,!goog.iter.Iterator<VALUE>):boolean} f
* The function to call for every value. This function takes 3 arguments
* (the value, undefined, and the iterator) and should return a boolean.
* @param {THIS=} opt_obj The object to be used as the value of 'this' within
* {@code f}.
* @return {boolean} true if any value passes the test.
* @template THIS, VALUE
*/
goog.iter.some = function(iterable, f, opt_obj) {
iterable = goog.iter.toIterator(iterable);
try {
while (true) {
if (f.call(opt_obj, iterable.next(), undefined, iterable)) {
return true;
}
}
} catch (ex) {
if (ex !== goog.iter.StopIteration) {
throw ex;
}
}
return false;
};
/**
* Goes through the values in the iterator. Calls f for each of these and if any
* of them returns false this returns false (without checking the rest). If all
* return true this will return true.
*
* @param {goog.iter.Iterator<VALUE>|goog.iter.Iterable} iterable The iterator
* object.
* @param {
* function(this:THIS,VALUE,undefined,!goog.iter.Iterator<VALUE>):boolean} f
* The function to call for every value. This function takes 3 arguments
* (the value, undefined, and the iterator) and should return a boolean.
* @param {THIS=} opt_obj The object to be used as the value of 'this' within
* {@code f}.
* @return {boolean} true if every value passes the test.
* @template THIS, VALUE
*/
goog.iter.every = function(iterable, f, opt_obj) {
iterable = goog.iter.toIterator(iterable);
try {
while (true) {
if (!f.call(opt_obj, iterable.next(), undefined, iterable)) {
return false;
}
}
} catch (ex) {
if (ex !== goog.iter.StopIteration) {
throw ex;
}
}
return true;
};
/**
* Takes zero or more iterables and returns one iterator that will iterate over
* them in the order chained.
* @param {...!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} var_args Any
* number of iterable objects.
* @return {!goog.iter.Iterator<VALUE>} Returns a new iterator that will
* iterate over all the given iterables' contents.
* @template VALUE
*/
goog.iter.chain = function(var_args) {
return goog.iter.chainFromIterable(arguments);
};
/**
* Takes a single iterable containing zero or more iterables and returns one
* iterator that will iterate over each one in the order given.
* @see https://goo.gl/5NRp5d
* @param {goog.iter.Iterable} iterable The iterable of iterables to chain.
* @return {!goog.iter.Iterator<VALUE>} Returns a new iterator that will
* iterate over all the contents of the iterables contained within
* {@code iterable}.
* @template VALUE
*/
goog.iter.chainFromIterable = function(iterable) {
var iterator = goog.iter.toIterator(iterable);
var iter = new goog.iter.Iterator();
var current = null;
iter.next = function() {
while (true) {
if (current == null) {
var it = iterator.next();
current = goog.iter.toIterator(it);
}
try {
return current.next();
} catch (ex) {
if (ex !== goog.iter.StopIteration) {
throw ex;
}
current = null;
}
}
};
return iter;
};
/**
* Builds a new iterator that iterates over the original, but skips elements as
* long as a supplied function returns true.
* @param {goog.iter.Iterator<VALUE>|goog.iter.Iterable} iterable The iterator
* object.
* @param {
* function(this:THIS,VALUE,undefined,!goog.iter.Iterator<VALUE>):boolean} f
* The function to call for every value. This function takes 3 arguments
* (the value, undefined, and the iterator) and should return a boolean.
* @param {THIS=} opt_obj The object to be used as the value of 'this' within
* {@code f}.
* @return {!goog.iter.Iterator<VALUE>} A new iterator that drops elements from
* the original iterator as long as {@code f} is true.
* @template THIS, VALUE
*/
goog.iter.dropWhile = function(iterable, f, opt_obj) {
var iterator = goog.iter.toIterator(iterable);
var newIter = new goog.iter.Iterator;
var dropping = true;
newIter.next = function() {
while (true) {
var val = iterator.next();
if (dropping && f.call(opt_obj, val, undefined, iterator)) {
continue;
} else {
dropping = false;
}
return val;
}
};
return newIter;
};
/**
* Builds a new iterator that iterates over the original, but only as long as a
* supplied function returns true.
* @param {goog.iter.Iterator<VALUE>|goog.iter.Iterable} iterable The iterator
* object.
* @param {
* function(this:THIS,VALUE,undefined,!goog.iter.Iterator<VALUE>):boolean} f
* The function to call for every value. This function takes 3 arguments
* (the value, undefined, and the iterator) and should return a boolean.
* @param {THIS=} opt_obj This is used as the 'this' object in f when called.
* @return {!goog.iter.Iterator<VALUE>} A new iterator that keeps elements in
* the original iterator as long as the function is true.
* @template THIS, VALUE
*/
goog.iter.takeWhile = function(iterable, f, opt_obj) {
var iterator = goog.iter.toIterator(iterable);
var iter = new goog.iter.Iterator();
iter.next = function() {
var val = iterator.next();
if (f.call(opt_obj, val, undefined, iterator)) {
return val;
}
throw goog.iter.StopIteration;
};
return iter;
};
/**
* Converts the iterator to an array
* @param {goog.iter.Iterator<VALUE>|goog.iter.Iterable} iterable The iterator
* to convert to an array.
* @return {!Array<VALUE>} An array of the elements the iterator iterates over.
* @template VALUE
*/
goog.iter.toArray = function(iterable) {
// Fast path for array-like.
if (goog.isArrayLike(iterable)) {
return goog.array.toArray(/** @type {!IArrayLike<?>} */ (iterable));
}
iterable = goog.iter.toIterator(iterable);
var array = [];
goog.iter.forEach(iterable, function(val) { array.push(val); });
return array;
};
/**
* Iterates over two iterables and returns true if they contain the same
* sequence of elements and have the same length.
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} iterable1 The first
* iterable object.
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} iterable2 The second
* iterable object.
* @param {function(VALUE,VALUE):boolean=} opt_equalsFn Optional comparison
* function.
* Should take two arguments to compare, and return true if the arguments
* are equal. Defaults to {@link goog.array.defaultCompareEquality} which
* compares the elements using the built-in '===' operator.
* @return {boolean} true if the iterables contain the same sequence of elements
* and have the same length.
* @template VALUE
*/
goog.iter.equals = function(iterable1, iterable2, opt_equalsFn) {
var fillValue = {};
var pairs = goog.iter.zipLongest(fillValue, iterable1, iterable2);
var equalsFn = opt_equalsFn || goog.array.defaultCompareEquality;
return goog.iter.every(
pairs, function(pair) { return equalsFn(pair[0], pair[1]); });
};
/**
* Advances the iterator to the next position, returning the given default value
* instead of throwing an exception if the iterator has no more entries.
* @param {goog.iter.Iterator<VALUE>|goog.iter.Iterable} iterable The iterable
* object.
* @param {VALUE} defaultValue The value to return if the iterator is empty.
* @return {VALUE} The next item in the iteration, or defaultValue if the
* iterator was empty.
* @template VALUE
*/
goog.iter.nextOrValue = function(iterable, defaultValue) {
try {
return goog.iter.toIterator(iterable).next();
} catch (e) {
if (e != goog.iter.StopIteration) {
throw e;
}
return defaultValue;
}
};
/**
* Cartesian product of zero or more sets. Gives an iterator that gives every
* combination of one element chosen from each set. For example,
* ([1, 2], [3, 4]) gives ([1, 3], [1, 4], [2, 3], [2, 4]).
* @see http://docs.python.org/library/itertools.html#itertools.product
* @param {...!IArrayLike<VALUE>} var_args Zero or more sets, as
* arrays.
* @return {!goog.iter.Iterator<!Array<VALUE>>} An iterator that gives each
* n-tuple (as an array).
* @template VALUE
*/
goog.iter.product = function(var_args) {
var someArrayEmpty =
goog.array.some(arguments, function(arr) { return !arr.length; });
// An empty set in a cartesian product gives an empty set.
if (someArrayEmpty || !arguments.length) {
return new goog.iter.Iterator();
}
var iter = new goog.iter.Iterator();
var arrays = arguments;
// The first indices are [0, 0, ...]
var indicies = goog.array.repeat(0, arrays.length);
iter.next = function() {
if (indicies) {
var retVal = goog.array.map(indicies, function(valueIndex, arrayIndex) {
return arrays[arrayIndex][valueIndex];
});
// Generate the next-largest indices for the next call.
// Increase the rightmost index. If it goes over, increase the next
// rightmost (like carry-over addition).
for (var i = indicies.length - 1; i >= 0; i--) {
// Assertion prevents compiler warning below.
goog.asserts.assert(indicies);
if (indicies[i] < arrays[i].length - 1) {
indicies[i]++;
break;
}
// We're at the last indices (the last element of every array), so
// the iteration is over on the next call.
if (i == 0) {
indicies = null;
break;
}
// Reset the index in this column and loop back to increment the
// next one.
indicies[i] = 0;
}
return retVal;
}
throw goog.iter.StopIteration;
};
return iter;
};
/**
* Create an iterator to cycle over the iterable's elements indefinitely.
* For example, ([1, 2, 3]) would return : 1, 2, 3, 1, 2, 3, ...
* @see: http://docs.python.org/library/itertools.html#itertools.cycle.
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} iterable The
* iterable object.
* @return {!goog.iter.Iterator<VALUE>} An iterator that iterates indefinitely
* over the values in {@code iterable}.
* @template VALUE
*/
goog.iter.cycle = function(iterable) {
var baseIterator = goog.iter.toIterator(iterable);
// We maintain a cache to store the iterable elements as we iterate
// over them. The cache is used to return elements once we have
// iterated over the iterable once.
var cache = [];
var cacheIndex = 0;
var iter = new goog.iter.Iterator();
// This flag is set after the iterable is iterated over once
var useCache = false;
iter.next = function() {
var returnElement = null;
// Pull elements off the original iterator if not using cache
if (!useCache) {
try {
// Return the element from the iterable
returnElement = baseIterator.next();
cache.push(returnElement);
return returnElement;
} catch (e) {
// If an exception other than StopIteration is thrown
// or if there are no elements to iterate over (the iterable was empty)
// throw an exception
if (e != goog.iter.StopIteration || goog.array.isEmpty(cache)) {
throw e;
}
// set useCache to true after we know that a 'StopIteration' exception
// was thrown and the cache is not empty (to handle the 'empty iterable'
// use case)
useCache = true;
}
}
returnElement = cache[cacheIndex];
cacheIndex = (cacheIndex + 1) % cache.length;
return returnElement;
};
return iter;
};
/**
* Creates an iterator that counts indefinitely from a starting value.
* @see http://docs.python.org/2/library/itertools.html#itertools.count
* @param {number=} opt_start The starting value. Default is 0.
* @param {number=} opt_step The number to increment with between each call to
* next. Negative and floating point numbers are allowed. Default is 1.
* @return {!goog.iter.Iterator<number>} A new iterator that returns the values
* in the series.
*/
goog.iter.count = function(opt_start, opt_step) {
var counter = opt_start || 0;
var step = goog.isDef(opt_step) ? opt_step : 1;
var iter = new goog.iter.Iterator();
iter.next = function() {
var returnValue = counter;
counter += step;
return returnValue;
};
return iter;
};
/**
* Creates an iterator that returns the same object or value repeatedly.
* @param {VALUE} value Any object or value to repeat.
* @return {!goog.iter.Iterator<VALUE>} A new iterator that returns the
* repeated value.
* @template VALUE
*/
goog.iter.repeat = function(value) {
var iter = new goog.iter.Iterator();
iter.next = goog.functions.constant(value);
return iter;
};
/**
* Creates an iterator that returns running totals from the numbers in
* {@code iterable}. For example, the array {@code [1, 2, 3, 4, 5]} yields
* {@code 1 -> 3 -> 6 -> 10 -> 15}.
* @see http://docs.python.org/3.2/library/itertools.html#itertools.accumulate
* @param {!goog.iter.Iterable} iterable The iterable of numbers to
* accumulate.
* @return {!goog.iter.Iterator<number>} A new iterator that returns the
* numbers in the series.
*/
goog.iter.accumulate = function(iterable) {
var iterator = goog.iter.toIterator(iterable);
var total = 0;
var iter = new goog.iter.Iterator();
iter.next = function() {
total += iterator.next();
return total;
};
return iter;
};
/**
* Creates an iterator that returns arrays containing the ith elements from the
* provided iterables. The returned arrays will be the same size as the number
* of iterables given in {@code var_args}. Once the shortest iterable is
* exhausted, subsequent calls to {@code next()} will throw
* {@code goog.iter.StopIteration}.
* @see http://docs.python.org/2/library/itertools.html#itertools.izip
* @param {...!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} var_args Any
* number of iterable objects.
* @return {!goog.iter.Iterator<!Array<VALUE>>} A new iterator that returns
* arrays of elements from the provided iterables.
* @template VALUE
*/
goog.iter.zip = function(var_args) {
var args = arguments;
var iter = new goog.iter.Iterator();
if (args.length > 0) {
var iterators = goog.array.map(args, goog.iter.toIterator);
iter.next = function() {
var arr = goog.array.map(iterators, function(it) { return it.next(); });
return arr;
};
}
return iter;
};
/**
* Creates an iterator that returns arrays containing the ith elements from the
* provided iterables. The returned arrays will be the same size as the number
* of iterables given in {@code var_args}. Shorter iterables will be extended
* with {@code fillValue}. Once the longest iterable is exhausted, subsequent
* calls to {@code next()} will throw {@code goog.iter.StopIteration}.
* @see http://docs.python.org/2/library/itertools.html#itertools.izip_longest
* @param {VALUE} fillValue The object or value used to fill shorter iterables.
* @param {...!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} var_args Any
* number of iterable objects.
* @return {!goog.iter.Iterator<!Array<VALUE>>} A new iterator that returns
* arrays of elements from the provided iterables.
* @template VALUE
*/
goog.iter.zipLongest = function(fillValue, var_args) {
var args = goog.array.slice(arguments, 1);
var iter = new goog.iter.Iterator();
if (args.length > 0) {
var iterators = goog.array.map(args, goog.iter.toIterator);
iter.next = function() {
var iteratorsHaveValues = false; // false when all iterators are empty.
var arr = goog.array.map(iterators, function(it) {
var returnValue;
try {
returnValue = it.next();
// Iterator had a value, so we've not exhausted the iterators.
// Set flag accordingly.
iteratorsHaveValues = true;
} catch (ex) {
if (ex !== goog.iter.StopIteration) {
throw ex;
}
returnValue = fillValue;
}
return returnValue;
});
if (!iteratorsHaveValues) {
throw goog.iter.StopIteration;
}
return arr;
};
}
return iter;
};
/**
* Creates an iterator that filters {@code iterable} based on a series of
* {@code selectors}. On each call to {@code next()}, one item is taken from
* both the {@code iterable} and {@code selectors} iterators. If the item from
* {@code selectors} evaluates to true, the item from {@code iterable} is given.
* Otherwise, it is skipped. Once either {@code iterable} or {@code selectors}
* is exhausted, subsequent calls to {@code next()} will throw
* {@code goog.iter.StopIteration}.
* @see http://docs.python.org/2/library/itertools.html#itertools.compress
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} iterable The
* iterable to filter.
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} selectors An
* iterable of items to be evaluated in a boolean context to determine if
* the corresponding element in {@code iterable} should be included in the
* result.
* @return {!goog.iter.Iterator<VALUE>} A new iterator that returns the
* filtered values.
* @template VALUE
*/
goog.iter.compress = function(iterable, selectors) {
var selectorIterator = goog.iter.toIterator(selectors);
return goog.iter.filter(
iterable, function() { return !!selectorIterator.next(); });
};
/**
* Implements the {@code goog.iter.groupBy} iterator.
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} iterable The
* iterable to group.
* @param {function(VALUE): KEY=} opt_keyFunc Optional function for
* determining the key value for each group in the {@code iterable}. Default
* is the identity function.
* @constructor
* @extends {goog.iter.Iterator<!Array<?>>}
* @template KEY, VALUE
* @private
*/
goog.iter.GroupByIterator_ = function(iterable, opt_keyFunc) {
/**
* The iterable to group, coerced to an iterator.
* @type {!goog.iter.Iterator}
*/
this.iterator = goog.iter.toIterator(iterable);
/**
* A function for determining the key value for each element in the iterable.
* If no function is provided, the identity function is used and returns the
* element unchanged.
* @type {function(VALUE): KEY}
*/
this.keyFunc = opt_keyFunc || goog.functions.identity;
/**
* The target key for determining the start of a group.
* @type {KEY}
*/
this.targetKey;
/**
* The current key visited during iteration.
* @type {KEY}
*/
this.currentKey;
/**
* The current value being added to the group.
* @type {VALUE}
*/
this.currentValue;
};
goog.inherits(goog.iter.GroupByIterator_, goog.iter.Iterator);
/** @override */
goog.iter.GroupByIterator_.prototype.next = function() {
while (this.currentKey == this.targetKey) {
this.currentValue = this.iterator.next(); // Exits on StopIteration
this.currentKey = this.keyFunc(this.currentValue);
}
this.targetKey = this.currentKey;
return [this.currentKey, this.groupItems_(this.targetKey)];
};
/**
* Performs the grouping of objects using the given key.
* @param {KEY} targetKey The target key object for the group.
* @return {!Array<VALUE>} An array of grouped objects.
* @private
*/
goog.iter.GroupByIterator_.prototype.groupItems_ = function(targetKey) {
var arr = [];
while (this.currentKey == targetKey) {
arr.push(this.currentValue);
try {
this.currentValue = this.iterator.next();
} catch (ex) {
if (ex !== goog.iter.StopIteration) {
throw ex;
}
break;
}
this.currentKey = this.keyFunc(this.currentValue);
}
return arr;
};
/**
* Creates an iterator that returns arrays containing elements from the
* {@code iterable} grouped by a key value. For iterables with repeated
* elements (i.e. sorted according to a particular key function), this function
* has a {@code uniq}-like effect. For example, grouping the array:
* {@code [A, B, B, C, C, A]} produces
* {@code [A, [A]], [B, [B, B]], [C, [C, C]], [A, [A]]}.
* @see http://docs.python.org/2/library/itertools.html#itertools.groupby
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} iterable The
* iterable to group.
* @param {function(VALUE): KEY=} opt_keyFunc Optional function for
* determining the key value for each group in the {@code iterable}. Default
* is the identity function.
* @return {!goog.iter.Iterator<!Array<?>>} A new iterator that returns
* arrays of consecutive key and groups.
* @template KEY, VALUE
*/
goog.iter.groupBy = function(iterable, opt_keyFunc) {
return new goog.iter.GroupByIterator_(iterable, opt_keyFunc);
};
/**
* Gives an iterator that gives the result of calling the given function
* <code>f</code> with the arguments taken from the next element from
* <code>iterable</code> (the elements are expected to also be iterables).
*
* Similar to {@see goog.iter#map} but allows the function to accept multiple
* arguments from the iterable.
*
* @param {!goog.iter.Iterable} iterable The iterable of
* iterables to iterate over.
* @param {function(this:THIS,...*):RESULT} f The function to call for every
* element. This function takes N+2 arguments, where N represents the
* number of items from the next element of the iterable. The two
* additional arguments passed to the function are undefined and the
* iterator itself. The function should return a new value.
* @param {THIS=} opt_obj The object to be used as the value of 'this' within
* {@code f}.
* @return {!goog.iter.Iterator<RESULT>} A new iterator that returns the
* results of applying the function to each element in the original
* iterator.
* @template THIS, RESULT
*/
goog.iter.starMap = function(iterable, f, opt_obj) {
var iterator = goog.iter.toIterator(iterable);
var iter = new goog.iter.Iterator();
iter.next = function() {
var args = goog.iter.toArray(iterator.next());
return f.apply(opt_obj, goog.array.concat(args, undefined, iterator));
};
return iter;
};
/**
* Returns an array of iterators each of which can iterate over the values in
* {@code iterable} without advancing the others.
* @see http://docs.python.org/2/library/itertools.html#itertools.tee
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} iterable The
* iterable to tee.
* @param {number=} opt_num The number of iterators to create. Default is 2.
* @return {!Array<goog.iter.Iterator<VALUE>>} An array of iterators.
* @template VALUE
*/
goog.iter.tee = function(iterable, opt_num) {
var iterator = goog.iter.toIterator(iterable);
var num = goog.isNumber(opt_num) ? opt_num : 2;
var buffers =
goog.array.map(goog.array.range(num), function() { return []; });
var addNextIteratorValueToBuffers = function() {
var val = iterator.next();
goog.array.forEach(buffers, function(buffer) { buffer.push(val); });
};
var createIterator = function(buffer) {
// Each tee'd iterator has an associated buffer (initially empty). When a
// tee'd iterator's buffer is empty, it calls
// addNextIteratorValueToBuffers(), adding the next value to all tee'd
// iterators' buffers, and then returns that value. This allows each
// iterator to be advanced independently.
var iter = new goog.iter.Iterator();
iter.next = function() {
if (goog.array.isEmpty(buffer)) {
addNextIteratorValueToBuffers();
}
goog.asserts.assert(!goog.array.isEmpty(buffer));
return buffer.shift();
};
return iter;
};
return goog.array.map(buffers, createIterator);
};
/**
* Creates an iterator that returns arrays containing a count and an element
* obtained from the given {@code iterable}.
* @see http://docs.python.org/2/library/functions.html#enumerate
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} iterable The
* iterable to enumerate.
* @param {number=} opt_start Optional starting value. Default is 0.
* @return {!goog.iter.Iterator<!Array<?>>} A new iterator containing
* count/item pairs.
* @template VALUE
*/
goog.iter.enumerate = function(iterable, opt_start) {
return goog.iter.zip(goog.iter.count(opt_start), iterable);
};
/**
* Creates an iterator that returns the first {@code limitSize} elements from an
* iterable. If this number is greater than the number of elements in the
* iterable, all the elements are returned.
* @see http://goo.gl/V0sihp Inspired by the limit iterator in Guava.
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} iterable The
* iterable to limit.
* @param {number} limitSize The maximum number of elements to return.
* @return {!goog.iter.Iterator<VALUE>} A new iterator containing
* {@code limitSize} elements.
* @template VALUE
*/
goog.iter.limit = function(iterable, limitSize) {
goog.asserts.assert(goog.math.isInt(limitSize) && limitSize >= 0);
var iterator = goog.iter.toIterator(iterable);
var iter = new goog.iter.Iterator();
var remaining = limitSize;
iter.next = function() {
if (remaining-- > 0) {
return iterator.next();
}
throw goog.iter.StopIteration;
};
return iter;
};
/**
* Creates an iterator that is advanced {@code count} steps ahead. Consumed
* values are silently discarded. If {@code count} is greater than the number
* of elements in {@code iterable}, an empty iterator is returned. Subsequent
* calls to {@code next()} will throw {@code goog.iter.StopIteration}.
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} iterable The
* iterable to consume.
* @param {number} count The number of elements to consume from the iterator.
* @return {!goog.iter.Iterator<VALUE>} An iterator advanced zero or more steps
* ahead.
* @template VALUE
*/
goog.iter.consume = function(iterable, count) {
goog.asserts.assert(goog.math.isInt(count) && count >= 0);
var iterator = goog.iter.toIterator(iterable);
while (count-- > 0) {
goog.iter.nextOrValue(iterator, null);
}
return iterator;
};
/**
* Creates an iterator that returns a range of elements from an iterable.
* Similar to {@see goog.array#slice} but does not support negative indexes.
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} iterable The
* iterable to slice.
* @param {number} start The index of the first element to return.
* @param {number=} opt_end The index after the last element to return. If
* defined, must be greater than or equal to {@code start}.
* @return {!goog.iter.Iterator<VALUE>} A new iterator containing a slice of
* the original.
* @template VALUE
*/
goog.iter.slice = function(iterable, start, opt_end) {
goog.asserts.assert(goog.math.isInt(start) && start >= 0);
var iterator = goog.iter.consume(iterable, start);
if (goog.isNumber(opt_end)) {
goog.asserts.assert(goog.math.isInt(opt_end) && opt_end >= start);
iterator = goog.iter.limit(iterator, opt_end - start /* limitSize */);
}
return iterator;
};
/**
* Checks an array for duplicate elements.
* @param {?IArrayLike<VALUE>} arr The array to check for
* duplicates.
* @return {boolean} True, if the array contains duplicates, false otherwise.
* @private
* @template VALUE
*/
// TODO(user): Consider moving this into goog.array as a public function.
goog.iter.hasDuplicates_ = function(arr) {
var deduped = [];
goog.array.removeDuplicates(arr, deduped);
return arr.length != deduped.length;
};
/**
* Creates an iterator that returns permutations of elements in
* {@code iterable}.
*
* Permutations are obtained by taking the Cartesian product of
* {@code opt_length} iterables and filtering out those with repeated
* elements. For example, the permutations of {@code [1,2,3]} are
* {@code [[1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], [3,2,1]]}.
* @see http://docs.python.org/2/library/itertools.html#itertools.permutations
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} iterable The
* iterable from which to generate permutations.
* @param {number=} opt_length Length of each permutation. If omitted, defaults
* to the length of {@code iterable}.
* @return {!goog.iter.Iterator<!Array<VALUE>>} A new iterator containing the
* permutations of {@code iterable}.
* @template VALUE
*/
goog.iter.permutations = function(iterable, opt_length) {
var elements = goog.iter.toArray(iterable);
var length = goog.isNumber(opt_length) ? opt_length : elements.length;
var sets = goog.array.repeat(elements, length);
var product = goog.iter.product.apply(undefined, sets);
return goog.iter.filter(
product, function(arr) { return !goog.iter.hasDuplicates_(arr); });
};
/**
* Creates an iterator that returns combinations of elements from
* {@code iterable}.
*
* Combinations are obtained by taking the {@see goog.iter#permutations} of
* {@code iterable} and filtering those whose elements appear in the order they
* are encountered in {@code iterable}. For example, the 3-length combinations
* of {@code [0,1,2,3]} are {@code [[0,1,2], [0,1,3], [0,2,3], [1,2,3]]}.
* @see http://docs.python.org/2/library/itertools.html#itertools.combinations
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} iterable The
* iterable from which to generate combinations.
* @param {number} length The length of each combination.
* @return {!goog.iter.Iterator<!Array<VALUE>>} A new iterator containing
* combinations from the {@code iterable}.
* @template VALUE
*/
goog.iter.combinations = function(iterable, length) {
var elements = goog.iter.toArray(iterable);
var indexes = goog.iter.range(elements.length);
var indexIterator = goog.iter.permutations(indexes, length);
// sortedIndexIterator will now give arrays of with the given length that
// indicate what indexes into "elements" should be returned on each iteration.
var sortedIndexIterator = goog.iter.filter(
indexIterator, function(arr) { return goog.array.isSorted(arr); });
var iter = new goog.iter.Iterator();
function getIndexFromElements(index) { return elements[index]; }
iter.next = function() {
return goog.array.map(sortedIndexIterator.next(), getIndexFromElements);
};
return iter;
};
/**
* Creates an iterator that returns combinations of elements from
* {@code iterable}, with repeated elements possible.
*
* Combinations are obtained by taking the Cartesian product of {@code length}
* iterables and filtering those whose elements appear in the order they are
* encountered in {@code iterable}. For example, the 2-length combinations of
* {@code [1,2,3]} are {@code [[1,1], [1,2], [1,3], [2,2], [2,3], [3,3]]}.
* @see https://goo.gl/C0yXe4
* @see https://goo.gl/djOCsk
* @param {!goog.iter.Iterator<VALUE>|!goog.iter.Iterable} iterable The
* iterable to combine.
* @param {number} length The length of each combination.
* @return {!goog.iter.Iterator<!Array<VALUE>>} A new iterator containing
* combinations from the {@code iterable}.
* @template VALUE
*/
goog.iter.combinationsWithReplacement = function(iterable, length) {
var elements = goog.iter.toArray(iterable);
var indexes = goog.array.range(elements.length);
var sets = goog.array.repeat(indexes, length);
var indexIterator = goog.iter.product.apply(undefined, sets);
// sortedIndexIterator will now give arrays of with the given length that
// indicate what indexes into "elements" should be returned on each iteration.
var sortedIndexIterator = goog.iter.filter(
indexIterator, function(arr) { return goog.array.isSorted(arr); });
var iter = new goog.iter.Iterator();
function getIndexFromElements(index) { return elements[index]; }
iter.next = function() {
return goog.array.map(
/** @type {!Array<number>} */
(sortedIndexIterator.next()), getIndexFromElements);
};
return iter;
};