Isaac Jones
I propose that each haskell compiler / interpreter come with runhaskell. It should check to see whether runhaskell exists already and if so, leave it alone. If not, provide it.
Shouldn't replacement be the default? I think a typical user will stick with one Haskell implementation, and just upgrade it once in a while - in which case replacement is probably what is desired. Anyway, I expect most users to install via OS packages (rpm,deb,..), and distributions tend to have their own solutions for this kind of thing (/etc/alternatives springs to mind).
That should probably be tweakable with the configure script.
'runhaskell' could perhaps also be a small script that checks for the availability of 'runhugs', 'runghc', etc. This way, it could be the same for all Haskell implementations, and the choice could be configurable on a user basis (rather than per system). It would cost a bit of startup time, though. -k -- If I haven't seen further, it is by standing in the footprints of giants