: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 : a function that decides which items should be in the new list
return value : a new list

:desc
Returns a list containing the members of 'items' for which 'f' returned boolean true.

:see
>string