module Ordered_collection_common:sig
..end
normalize length_fun thing_with_length i
is just i
, unless
i
is negative, in which case it's length_fun thing_with_length + i
.
This is used by various python-style slice functions.val normalize : length_fun:('a -> int) -> 'a -> int -> int
val slice : length_fun:('a -> int) ->
sub_fun:('a -> pos:int -> len:int -> 'a) -> 'a -> int -> int -> 'a
val get_pos_len_exn : ?pos:int -> ?len:int -> length:int -> int * int
get_pos_len
and get_pos_len_exn
are intended to be used by functions
that take a sequence (array, string, bigstring, ...) and an optional pos
and len
specifying a subrange of the sequence. Such functions should call
get_pos_len
with the length of the sequence and the optional pos
and
len
, and it will return the pos
and len
specifying the range, where
the default pos
is zero and the default len
is to go to the end of the
sequence.
It should be the case that:
0 <= pos <= length len >= 0 pos + len <= length
Note that this allows pos = length
and len = 0
, i.e. an empty subrange
at the end of the sequence.
get_pos_len
returns (pos', len')
specifying a subrange where:
pos' = match pos with None -> 0 | Some i -> i
len' = match len with None -> length - pos | Some i -> i
val get_pos_len : ?pos:int -> ?len:int -> length:int -> (int * int, string) Result.t