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Iteration primitives using generators

This library implements iteration primitives like map() and filter() using generators. To a large part this serves as a repository for small examples of generator usage, but of course the functions are also practically quite useful.

All functions in this library accept arbitrary iterables, i.e. arrays, traversables, iterators and aggregates, which makes it quite different from functions like array_map() (which only accept arrays) and the SPL iterators (which usually only accept iterators, not even aggregates). The operations are of course lazy.


To install with composer:

composer require nikic/iter


A small usage example for the map() and range() functions:


use iter\func;

require 'path/to/vendor/autoload.php';

$nums = iter\range(1, 10);
$numsTimesTen = iter\map(func\operator('*', 10), $nums);
// => iter(10, 20, 30, 40, 50, 60, 70, 80, 90, 100)

You can find documentation and usage examples for the individual functions in iter.php, here I only list the function signatures as an overview:

Iterator map(callable $function, iterable $iterable)
Iterator mapWithKeys(callable $function, iterable $iterable)
Iterator mapKeys(callable $function, iterable $iterable)
Iterator flatMap(callable $function, iterable $iterable)
Iterator reindex(callable $function, iterable $iterable)
Iterator filter(callable $predicate, iterable $iterable)
Iterator enumerate(iterable $iterable)
Iterator toPairs(iterable $iterable)
Iterator fromPairs(iterable $iterable)
Iterator reductions(callable $function, iterable $iterable, mixed $startValue = null)
Iterator zip(iterable... $iterables)
Iterator zipKeyValue(iterable $keys, iterable $values)
Iterator chain(iterable... $iterables)
Iterator product(iterable... $iterables)
Iterator slice(iterable $iterable, int $start, int $length = INF)
Iterator take(int $num, iterable $iterable)
Iterator drop(int $num, iterable $iterable)
Iterator takeWhile(callable $predicate, iterable $iterable)
Iterator dropWhile(callable $predicate, iterable $iterable)
Iterator keys(iterable $iterable)
Iterator values(iterable $iterable)
Iterator flatten(iterable $iterable, int $levels = INF)
Iterator flip(iterable $iterable)
Iterator chunk(iterable $iterable, int $size, bool $preserveKeys = false)
Iterator chunkWithKeys(iterable $iterable, int $size)
Iterator tap(callable $function, iterable $iterable)
Iterator toIter(iterable $iterable)

Iterator range(number $start, number $end, number $step = null)
Iterator repeat(mixed $value, int $num = INF)
Iterator split(string $separator, string $data)

mixed    reduce(callable $function, iterable $iterable, mixed $startValue = null)
bool     any(callable $predicate, iterable $iterable)
bool     all(callable $predicate, iterable $iterable)
mixed    search(callable $predicate, iterable $iterable)
void     apply(callable $function, iterable $iterable)
string   join(string $separator, iterable $iterable)
int      count(iterable $iterable)
bool     isEmpty(iterable $iterable)
mixed    recurse(callable $function, $iterable)
array    toArray(iterable $iterable)
array    toArrayWithKeys(iterable $iterable)
bool     isIterable($value)

As the functionality is implemented using generators the resulting iterators are by default not rewindable. This library implements additional functionality to allow creating rewindable generators.

You can find documentation for this in iter.rewindable.php, here is just a small usage example of the two main functions:


use iter\func;

require 'path/to/vendor/autoload.php';

/* Create a rewindable map function which can be used multiple times */
$rewindableMap = iter\makeRewindable('iter\\map');
$res = $rewindableMap(func\operator('*', 3), [1, 2, 3]);

/* Do a rewindable call to map, just once */
$res = iter\callRewindable('iter\\map', func\operator('*', 3), [1, 2, 3]);

The above functions are only useful for your own iterators though; for the iter iterators, rewindable variants are directly provided with an iter\rewindable prefix:

$res = iter\rewindable\map(func\operator('*', 3), [1, 2, 3]);
// etc