/**
* We could also use the catamorphism on this to do recursion, as we
* have an unfix and an underlying fmap from the FDirectory.
*
* Supply a function $trans from File|FDirectory a to a that flattens
* (folds) a directory. Will start the directories where only files are
* included, folds them and then proceeds upwards.
*
* The return type should be 'a' (from the function $trans) instead
* of mixed, but we can't express that fact correctly in the docstring
* typing.
*
* @param \Closure $trans File|FDirectory a -> a
* @return mixed
*/
public function cata(\Closure $trans)
{
return $trans($this->directory->unfix()->fmap(function (FSObject $obj) use($trans) {
if ($obj->isFile()) {
return $trans($obj);
}
assert($obj instanceof FixedFDirectory);
return $obj->cata($trans);
}));
}
