QuickCheck vs WinHugs

[Ross Paterson]

On Sat, Nov 12, 2005 at 07:07:09PM +0000, Neil Mitchell wrote:
> The progress display in QuickCheck doesn't work in the latest version
> of WinHugs. It remains entirely blank until the end, not displaying
> the number it is on.
> 
> Having looked at the source code to quickcheck, it is interacting with
> the WinHugs notion of "\b" very badly. In WinHugs \b is treated as
> phycially delete the last character that was written out on the
> console, removing it. QuickCheck seems to expect the behaviour of \b
> to be move the cursor to the left by one position, but do not erase
> the text that was to the right of the \b character.
> 
> What should the correct behaviour be, while the \b character is
> mentioned in the Haskell report, its behaviour is not.

I think ANSI specifies \b as moving the carriage to the left and \DEL
as erasing the character from the paper tape.

Under Unix the default behaviour is:

- if the user types BackSpace, the character to the left of the cursor
  is erased and the cursor moves left (unless there are no pending
  user-typed characters).

- if the program outputs '\b' to the console, the cursor is moved one
  position to the left, with no erasure.

Is that feasible?