mixed *map_array(mixed *arr, string fun, object ob, mixed extra)

Returns an array holding the items of <arr> mapped through ob->fun().
The function <fun> in <ob> is called for each element in <arr> with that
element as parameter. A second parameter <extra> is sent in each call if
given. Principal function: 
	foreach (index) arr[index] = ob->fun(arr[index],extra);

The value returned by ob->fun(arr[.index.], extra) replaces the existing 
element in the array. If <arr> is not an array, then 0 will be returned.

See also: LPC/arrays