ndmitchell:
Hi
Optimisation and ghci don't go together, so I don't know what your point is there.
It's very worth having the application work in both Hugs and GHCi, and its not always GHC=faster, only if you compile it - so you trade your compile time for your run time. A delicate balance, with more than one local optima.
But you'd always compile the code if you cared about performance anyway. 20 years of optimisation technology only comes into play then.
Anyway, its the same with ByteString -- we have it work in ghci or hugs or nhc, but its only worth actually optimising for GHC.
Can you use overloaded Strings with Hugs? I am not aware of how to. I am happy to use RULES's and pragmas etc, but I can't see a way of doing overloaded strings this way, as by the time I've got to RULES I've gained the unpackCString, which just won't go away!
You'd have to conditionally use overloaded strings in GHC only. I'm not sure it would work ( can you quantify the cost of not being able to take head at compile time? ) -- Don