filter - select certain elements

mixed filter(mixed x, string fun, object ob, mixed extra, ...);

mixed filter(mixed x, function f, mixed extra, ...);

The (ob, fun) syntax works as if (: call_other, ob, fun :) had been passed as
f.  Filter returns a new structure containing only the elements of x for which
the function returns nonzero.  Currently, it can be used on arrays and
mappings.  In the case of mappings, both the key and the value are passed
to the function.  extra and all the following arguments are passed to the
function after the element.  For example, filter(arr, fun, 2, 3) will
first call fun(arr[0], 2, 3) then fun(arr[1], 2, 3) etc.

 Tim Hollebeek  Beek@ZorkMUD, Lima Bean, IdeaExchange, and elsewhere
