It's been a while. Still looking for work, but I'm happy to say that there is now a Des Moines area meetup for people learning Haskell, so that I'm going through Haskell Programming from First Principles more seriously this time and doing all the exercises.
Thanks to that, I realize that one can express the one well-behaved function of type a -> b -> a as curry fst, but I am confused by one problem (so far). It's the first of a set that has the student modify a type signature and see how it affects the binding of a particular expression to the variable whose type signature is changed. Initially we have
i :: Num a => a
i = 1
and the change is to
i :: a
i = 1
The first one clearly works; Num a => a is the type of numerical constants (without decimal points) in Haskell. The second, if you try it, fails, with ghci nudging you to put back the typeclass constraint... but at this point my time working on compilers comes back to me, and I recall the following: semantically, passing a parameter to a function is assignment. You assign the actual parameter to the corresponding formal parameter (really, you put it where the ABI says the parameter should go for the called function to get to it).
So... if you can't assign 1 to i when i's type signature is a, why can you pass 1 to id? Haskell must treat the two differently. Looks like I just have to find out what the difference is.
