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[Sequence] Add "terminal" methods: aggregation #32

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Merged
delacry merged 2 commits into from
Sep 17, 2026
Merged

[Sequence] Add "terminal" methods: aggregation #32

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46f3c96
Add sequence aggregation terminals
nikophil Aug 24, 2026
5aa3aa5
Address review on sequence aggregation terminals
nikophil Sep 16, 2026
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232 changes: 0 additions & 232 deletions src/CollectionLogic.php
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Original file line number Diff line number Diff line change
Expand Up @@ -10,10 +10,8 @@
namespace Noctud\Collection;

use Closure;
use Noctud\Collection\Exception\ConversionException;
use Noctud\Collection\Exception\NoSuchElementException;
use Noctud\Collection\Exception\UnsupportedOperationException;
use Stringable;
use Noctud\Collection\List\ImmutableList;
use Noctud\Collection\List\MutableList;
use Noctud\Collection\Map\ImmutableMap;
Expand Down Expand Up @@ -159,236 +157,6 @@ public function count(): int

// --- Aggregation ---

/** {@inheritDoc} */
public function fold(mixed $initial, Closure $operation): mixed
{
$acc = $initial;
foreach ($this as $v) {
$acc = $operation($acc, $v);
}
return $acc;
}

/** {@inheritDoc} */
public function reduce(Closure $operation): mixed
{
$first = true;
$acc = null;

foreach ($this as $v) {
if ($first) {
$acc = $v;
$first = false;
} else {
$acc = $operation($acc, $v);
}
}

if ($first) {
throw new UnsupportedOperationException();
}

return $acc;
}

/** {@inheritDoc} */
public function reduceOrNull(Closure $operation): mixed
{
try {
return $this->reduce($operation);
} catch (UnsupportedOperationException) {
return null;
}
}

/** {@inheritDoc} */
// @phpstan-ignore conditionalType.subjectNotFound (E is concrete, not a template, in extending fixtures)
public function sum(?Closure $selector = null): int|float
{
$sum = 0;
foreach ($this as $i => $v) {
$sum += $selector !== null ? $selector($v, $i) : $v; // @phpstan-ignore assignOp.invalid
}

return $sum;
}

/** {@inheritDoc} */
public function avg(?Closure $selector = null): float
{
return $this->avgOrNull($selector) ?? throw new UnsupportedOperationException('Cannot compute average of empty collection');
}

/** {@inheritDoc} */
public function avgOrNull(?Closure $selector = null): float|null
{
$sum = 0;
$count = 0;
foreach ($this as $i => $v) {
$sum += $selector !== null ? $selector($v, $i) : $v; // @phpstan-ignore assignOp.invalid
$count++;
}

return $count > 0 ? $sum / $count : null;
}

/** {@inheritDoc} */
public function min(?Closure $selector = null): mixed
{
$minValue = null;
$minElement = null;
$found = false;

foreach ($this as $i => $v) {
$value = $selector !== null ? $selector($v, $i) : $v;
if (!$found || $value < $minValue) {
$minValue = $value;
$minElement = $v;
$found = true;
}
}

if (!$found) {
throw new NoSuchElementException('Collection is empty');
}

return $minElement;
}

/** {@inheritDoc} */
public function minOrNull(?Closure $selector = null): mixed
{
try {
return $this->min($selector);
} catch (NoSuchElementException) {
return null;
}
}

/** {@inheritDoc} */
public function max(?Closure $selector = null): mixed
{
$maxValue = null;
$maxElement = null;
$found = false;

foreach ($this as $i => $v) {
$value = $selector !== null ? $selector($v, $i) : $v;
if (!$found || $value > $maxValue) {
$maxValue = $value;
$maxElement = $v;
$found = true;
}
}

if (!$found) {
throw new NoSuchElementException('Collection is empty');
}

return $maxElement;
}

/** {@inheritDoc} */
public function maxOrNull(?Closure $selector = null): mixed
{
try {
return $this->max($selector);
} catch (NoSuchElementException) {
return null;
}
}

/** {@inheritDoc} */
public function minOf(Closure $selector): mixed
{
$minValue = null;
$found = false;

foreach ($this as $i => $v) {
$value = $selector($v, $i);
if (!$found || $value < $minValue) {
$minValue = $value;
$found = true;
}
}

if (!$found) {
throw new NoSuchElementException('Collection is empty');
}

return $minValue;
}

/** {@inheritDoc} */
public function minOfOrNull(Closure $selector): mixed
{
try {
return $this->minOf($selector);
} catch (NoSuchElementException) {
return null;
}
}

/** {@inheritDoc} */
public function maxOf(Closure $selector): mixed
{
$maxValue = null;
$found = false;

foreach ($this as $i => $v) {
$value = $selector($v, $i);
if (!$found || $value > $maxValue) {
$maxValue = $value;
$found = true;
}
}

if (!$found) {
throw new NoSuchElementException('Collection is empty');
}

return $maxValue;
}

/** {@inheritDoc} */
public function maxOfOrNull(Closure $selector): mixed
{
try {
return $this->maxOf($selector);
} catch (NoSuchElementException) {
return null;
}
}

/** {@inheritDoc} */
public function joinToString(string $separator = ', ', string $prefix = '', string $postfix = '', int $limit = -1, string $truncated = '...', ?Closure $transform = null): string
{
$parts = [];
$i = 0;
foreach ($this as $v) {
if ($limit >= 0 && $i >= $limit) {
$parts[] = $truncated;
break;
}

if ($transform !== null) {
$parts[] = $transform($v, $i);
} elseif (is_scalar($v) || $v === null || $v instanceof Stringable) {
$parts[] = (string) $v;
} else {
throw new ConversionException(sprintf(
'Value of type "%s" at index %d cannot be converted to string. Provide a $transform closure to resolve.',
get_debug_type($v),
$i
));
}

$i++;
}

return $prefix . implode($separator, $parts) . $postfix;
}

/** {@inheritDoc} */
#[NoDiscard]
public function countBy(Closure $keySelector): ImmutableMap
Expand Down
20 changes: 20 additions & 0 deletions src/Exception/UnsupportedOperationException.php
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Original file line number Diff line number Diff line change
Expand Up @@ -10,11 +10,31 @@
namespace Noctud\Collection\Exception;

use LogicException;
use Noctud\Collection\Collection;
use Noctud\Collection\Sequence\Sequence;

/**
* Thrown when a mutating method is called on an immutable collection/map or when a
* requested operation is not valid in the current state (e.g., removing from an empty list).
*/
class UnsupportedOperationException extends LogicException
{
use NamesItsSubject;

/**
* @param Collection<mixed>|Sequence<mixed> $subject
*/
public static function cannotReduceEmptySubject(Collection|Sequence $subject): self
{
return new self(sprintf('Cannot reduce empty %s', lcfirst(self::subjectName($subject))));
}

/**
* @param Collection<mixed>|Sequence<mixed> $subject
*/
public static function cannotAverageEmptySubject(Collection|Sequence $subject): self
{
// Mid-sentence, so the noun is lowercased - which leaves the eager message untouched.
return new self(sprintf('Cannot compute average of empty %s', lcfirst(self::subjectName($subject))));
}
}
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