@select_map(m:map, f:funct)
build a new map containing the entries of m which satisfy predicate f. This predicate takes two arguments: the key and the value. For instance 
       @fun_def pred($key, $value) { return ($key > "b") && ($value < 4) }
       $m := MAP{ ("a", 1), ("b", 2), ("c", 3), ("d", 4) }
       $mm := @select_map($m, @pred)
       print $mm
displays MAP{ ("c", 3) }

See also Map (aka dictionnary) @add_pair,    @clear,    @count,    @domain,    @find,    @gshift_map,    @insert,    @is_defined,    @is_function,    @is_map,    @listify,    @make_duration_map,    @make_label_bpm,    @make_label_duration,    @make_label_pitches,    @make_label_pos,    @make_score_map,    @map,    @map_compose,    @map_concat,    @map_history,    @map_history_date,    @map_history_rdate,    @map_normalize,    @map_reverse,    @mapval,    @max_key,    @max_val,    @member,    @merge,    @min_key,    @min_val,    @occurs,    @range,    @remove,    @select_map,    @shift_map