distinct()

The distinct operator emits only items that are unique, preserving FIFO order. By default, items are compared using the strict equality operator (===).

Optionally, you may provide a callable that computes an identity for each item based on its value and key. When provided, distinctness is determined by performing strict equality comparisons on the computed identities instead of the original items.

Warning

The memory consumption of this operator depends on the number of distinct items emitted by the upstream. As a result, it is considered memory-unsafe, since memory usage can grow without bound for unbounded streams.

class RunOpenCode\Component\Dataset\Operator\Distinct
__construct(iterable<TKey, TValue> $source, ?callable(TValue, TKey=): string $identity = null)
Parameters:

  • $source – iterable<TKey, TValue> Stream to iterate over.

  • $identity – ?callable(TValue, TKey=): string User defined callable to determine item identity. If null, strict comparison (===) of values is used.

getIterator()
Returns:

\Traversable<TKey, TValue> Distinct items from the stream source (distinct by value or by identity).

Use cases

  • Use this operator to eliminate duplicate items from a stream.

Example

 1<?php
 2
 3new Stream((static function(): iterable {
 4        yield 'a' => 1;
 5        yield 'a' => 2;
 6        yield 'a' => 1;
 7        yield 'b' => 1;
 8        yield 'b' => 1;
 9    })())
10    ->distinct(static fn(int $value, string $key): string => \sprintf('%s_%d', $key, $value));
11
12// preserves: 'a' => 1, 'a' => 2, 'b' => 1