Readline read_history and write_history addition

[Judah Jacobson]

> On Jan 19, 2008 11:09 AM, Judah Jacobson <judah.jacobson at gmail.com> wrote:
> >
> > On Jan 18, 2008 11:10 PM, Alexander Dunlap <alexander.dunlap at gmail.com> wrote:
> > > Hello all,
> > >
> > > I'd like to propose the addition of read_history and write_history
> > > bindings to the readline library. I believe I've followed the
> > > instructions on the Haskell wiki appropriately and I've set up a
> > > ticket (with a patch) at
> > > http://hackage.haskell.org/trac/ghc/ticket/2053.
> > >
> > > Essentially, the patch adds simple bindings so that Haskell programs
> > > can use Readline's read_history and write_history functions. This will
> > > be useful for the implementation of
> > > http://hackage.haskell.org/trac/ghc/ticket/2050 (add persistent
> > > history to GHCi) and potentially other applications.
> > >
> > > Thanks for your time and consideration.
> > >
> > > Alex
> >
> > That patch looks good to me.  While we're at it, can we also add the
> > following related functions, which are used to control the maximum
> > size of the history file?  (They're also provided by editline.)
> >
> > void             clear_history(void);
> > void             stifle_history(int);
> > int              unstifle_history(void);
> > int              history_is_stifled(void);
> >

One more suggestion, from Robert Dockins (author of the Shellac and
Shellac-readline packages):

> The only concern I have is that this patch doesn't seem to
> be handling errors properly.  read_history and write_history should return
> errno, but this binding has them returning ().  These functions do file
> operations and therefore can fail; we want (be able) to know when that
> happens.

I think we should just throw an error if those functions return a
nonzero value; for example, we already do that in the functions
readInitFile and parseAndBind.

Thanks,
-Judah