@gshift_map(a:map, f:function)
f
can be a map, a nim or an intentional function),
builds a new map b
such that
b(f(x)) = a(x)
See also Map (aka dictionnary) @add_pair @clear [@clone] @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