:sig
StringList filter(StringList items, function<bool (String)> f)
vector<T> filter(vector<T> items, function<bool (T)> f)

:params
items : list of items to be filtered
f : predicate function; items are kept when this returns `true`
return value : a new list

:see
>string

:content
Returns a new list containing the members of `items` for which `f` returned `true`.

## Related Concepts

- PHP: `array_filter()` for arrays or custom predicate-based filtering over strings and collections
- JavaScript / Node.js: `Array.prototype.filter()` and custom predicate helpers
