group_map_reduce
Sequence.group_map_reduce
(K
type
:
property.orderable, B type
, key_f Unary K T, f Unary B T, reduce_f Binary B B B) =>
container.Map K B¶Type Parameters
type of the keys
0.097dev (GIT hash 6a5de4939ddf29875c1d9a706508d9bfd0cd7ca9)
reduce elements within a group by first applying f and then using reduce_f to reduce
example: count occurrences of letters, numbers and other characters
=> {(digit => 2), (letter => 3), (other => 1)}