[Haskell-cafe] if-then-else as rebindable syntax (was Re: Why does Haskell have the if-then-else syntax?)

[Simon Peyton-Jones]

| We alreday are at a stage where first year students trying to master
| haskell get error messages like
| 
| "Bool is not an instance of the class Num"
| 
| if they accidently write 1 + True (or something equivalent, but less
| obvious).
| 
| If you want to mess around why not call the function "provided" or
| something similar.

Just to be clear, to get rebindable syntax in GHC today, you have to ask
for it explicitly, via
	-fno-implicit-prelude

If you use that flag, you'd better know what it means.  It already means
that do-notation uses whatever (>>) and (>>=) are in scope, not
Control.Monad.(>>) etc.  This if-thing is just another example.

No beginner will encounter this complication; they'd have to ask for it.

Simon