[Ocaml-lib-devel] Re: ExtString.String.slice bug

[Bardur A. <sp...@sc...>]

Brian Brunswick wrote:
> Hi, thanks for extlib!
> 
> ExtString.String.slice doesn't live up to its documentation of never
> raising an exception. It fails to check if ~last is out of range, and
> crashes in String.sub.
> 
> Is it best to report bugs here, or in the tracker?
> 
> --

I notice there's been no commit to the CVS with a fix for this even 
though the bug was reported quite a long time ago, so I'm going to 
commit this cleaned up and corrected version later today/tomorrow if 
there are no objections:

     let clip _min _max x =
       max _min (min _max x)
     ;;

     let slice ?(first=0) ?(last=Sys.max_string_length) s =
       let i =
         clip 0 (length s)
           (if (first<0) then
              (length s) + first
            else
              first)
       and j =
         clip 0 (length s)
           (if (last<0) then
              (length s) + last
            else
              last)
       in
         if i>=j || i=length s then
           create 0
         else
           sub s i (j-i)


Btw, John Skaller is correct in that the behavior was intended to be 
exactly like Python's slice operator.

-- 
Bardur Arantsson
<ba...@im...>
<ba...@sc...>

- And the best part? I didn't learn a thing.