/**
* Map an array or traversable to another array.
*
* @param callable $mapper a mapper to map each value;
* value will be passed to the mapper as the first argument,
* key will be passed as the second one
* @param array|\Traversable $traversable the traversable to map
* @param bool $with_keys pass key to the mapper as second argument
* (optional, default is false)
* @return array the mapped array
*/
function traversable_map(callable $mapper, $traversable, bool $with_keys = false) : array
{
$array_mapped = [];
foreach (to_traversable($traversable) as $key => $value) {
$array_mapped[$key] = $with_keys ? call_user_func($mapper, $value, $key) : call_user_func($mapper, $value);
}
return $array_mapped;
}
/**
* Iteratively reduce an array or a traversable to a single value
* using a callback function.
*
* Function applies iteratively the callback function to elements and keys
* of the array or the traversable, so as to reduce it to a single value.
*
* @param callable $callback the callback to apply to each element and key;
* current intermediate result will be passed as the first argument
* (in the case of the first iteration it instead holds the value of
* <code>$initial</code>), current value will be passed as the second one,
* current key will be passed as the third one; callback must return
* new intermediate result
* @param mixed $initial initial value
* @param array|\Traversable $traversable the input traversable
* @return mixed the resulting value
*/
function traversable_reduce(callable $callback, $initial, $traversable)
{
$result = $initial;
foreach (to_traversable($traversable) as $key => $value) {
$result = call_user_func($callback, $result, $value, $key);
}
return $result;
}
/**
* Filter an array or a traversable.
*
* @param callable $predicate a predicate to test each value and key;
* value will be passed to the predicate as the first argument,
* key will be passed as the second one
* @param array|\Traversable $traversable the traversable to filter
* @param bool $with_keys pass key to the predicate as second argument
* (optional, default is false)
* @return array the filtered array
*/
function traversable_filter(callable $predicate, $traversable, bool $with_keys = false) : array
{
$array_filtered = [];
foreach (to_traversable($traversable) as $key => $value) {
$result = $with_keys ? call_user_func($predicate, $value, $key) : call_user_func($predicate, $value);
if (!$result) {
continue;
}
$array_filtered[$key] = $value;
}
return $array_filtered;
}
/**
* Walk on an array or traversable.
*
* @param callable $action an action to perform with each item and key of the traversable;
* value will be passed to the action as the first argument,
* key will be passed as the second one
* @param array|\Traversable $traversable the traversable to walk on
*/
function traversable_walk(callable $action, $traversable)
{
foreach (to_traversable($traversable) as $key => $value) {
call_user_func($action, $value, $key);
}
}