init len f creates a new storage. the returned storage has length
len, its nth-element is
f is called with integers
0 ... len - 1, only once for each integer. The call is in the increasing order f 0, f 1, f 2, ...
val length : t -> int
The number of Unicode characters in the storage
next x i, prev x i : The operation is valid if
i points the valid element, i.e. the returned value may point the location beyond valid elements by one. If
i does not point a valid element, the results are unspecified.
move t i n : if
n >= 0, then returns
n-th character after
i and otherwise returns -
n-th character before
i. If there is no such character, or
i does not point a valid character, the result is unspecified.
compare_index t i j returns a positive integer if
i is the location placed after
t, 0 if
j point the same location, and a negative integer if
i is the location placed before
module Buf : sig ... end
Character buffers. Similar to Buffer.