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Thread-Topic: Proposal: Adding a RewindableKeyValueIterator type allowing
 mixed/repeated keys
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Date: Sun, 31 Jan 2021 00:36:59 +0000
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Subject: Proposal: Adding a RewindableKeyValueIterator type allowing
 mixed/repeated keys
From: tysonandre775@hotmail.com (tyson andre)

Hi internals,=0A=
=0A=
Currently, there don't seem to be any internal classes that can be used to =
store a copy of the keys and values of an arbitrary Traversable.=0A=
=0A=
-=A0This would help in eagerly evaluating the result of a generator in a me=
mory efficient way that could be exactly stored and reused =0A=
  e.g. `return $this->cachedResults ??=3D new \RewindableKeyValueIterator($=
this->innerResultsGenerator());`=0A=
  https://externals.io/message/108767#108797=0A=
- This would be useful to exactly represent the keys of sequences with repe=
ated keys (e.g. `yield 'first'; yield 'second';` implicitly uses the key `0=
` twice.)=0A=
- This would be convenient to have to differentiate between 1, '1', and tru=
e.=0A=
- This would be useful if php were to add internal global functions that ac=
t on iterables and return Traversables with potentially repeated keys based=
 on those iterables,=0A=
   e.g. map(), filter(), take(), flip(), etc=0A=
- If PHP were to add more iterable methods, being able to save an immutable=
 copy of a traversable's result would be useful for end users.=0A=
- If PHP were to add a Map (ordered hash map with null/any scalar/arrays/ob=
jects as keys) class type in the future,=0A=
  and that implemented IteratorAggregate, the return type of getIterator() =
would need something like RewindableKeyValueIterator.=0A=
- The lack of a relevant datatype is among the reasons why classes such as =
SplObjectStorage are still an Iterator instead of an IteratorAggregate. (an=
d backwards compatibility)=0A=
=0A=
```=0A=
final class KeyValueSequenceIterator implements Iterator {=0A=
    // loop over all values in $values and store a copy, converting=0A=
    // references in top-level array values to non-references=0A=
    public function __construct(iterable $values) {...}=0A=
    public static function fromKeyValuePairs(iterable $entries): self {...}=
 // fromKeyValuePairs([[$key1, $value1]])=0A=
    public function rewind(): void {...}=0A=
    public function next(): void {...}=0A=
    public function current(): mixed {...}=0A=
    public function key(): mixed {...}=0A=
    public function valid(): bool {...}=0A=
    // and __debugInfo, __clone(), etc.=0A=
}=0A=
```=0A=
=0A=
Thanks,=0A=
- Tyson=