map()  - modify an mapping, array, or string via application of a func‐
tion

mapping map( mapping | mixed* | string x, string fun, object ob,
             mixed extra, ... );
mapping map( mapping | mixed* | string x, function f, mixed extra, ... );

If the first argument is a mapping, map() behaves exactly like map_map‐
ping().  If it is an array, map() behaves exactly like map_array().  If
it's argument is a string, map() passes each character (as an  int)  to
the  function,  and replaces the character with the return value if the
return value is a non-zero integer.

filter_array(3), sort_array(3), map_array(3), map_mapping(3)