Library proposal: add a Location interface for element-wise operations on Data.Map (#4887)

Iavor Diatchki iavor.diatchki at
Sun Jan 9 00:55:42 CET 2011

I think that Henning probably meant that those functions should return a
value of type Maybe (a, Location k a): Nothing when the Map is empty, and
Just (...) otherwise.  This seems like a good idea to me.  The API looks
nice otherwise.

On Sat, Jan 8, 2011 at 7:28 AM, Ross Paterson <ross at> wrote:

> On Sat, Jan 08, 2011 at 04:21:54PM +0100, Henning Thielemann wrote:
> > On Sat, 8 Jan 2011, Ross Paterson wrote:
> > >That would work well for search, but then index, minLocation and
> maxLocation
> > >would return Locations that value was always mapped to Just something.
> > >Extra invariants like that feel wrong to me.
> >
> > 'index' can be out of range and then return Nothing. minLocation and
> > maxLocation return Nothing if the Map is empty.
> But what is the key in those cases?
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