Just for your fun and horror
Manuel M. T. Chakravarty
Sun, 18 Feb 2001 14:50:16 +1100
Jon Fairbairn <[email protected]> wrote,
> On Fri, 16 Feb 2001, Scott Turner wrote:
> > Just because the type system of C keeps store implicit, it doesn't
> > change the match between the meaning of 'return' in the two languages.
> Or to put it another way, _all_ types in C are IO
> something. I think from a didactic point of view making
> this observation could be very valuable.
I absolutely agree. The Haskell
foo :: IO Int
foo = return 42
int foo ()
are exactly the same. It is
bar = 42
for which C has no corresponding phrase. So, it is a new
concept, which for the students - not surprisingly - is an
In fact, I think, there is a second lesson in the whole
story, too: Syntax is just...well...syntax. Students
knowing only one or possibly two related languages, often
cannot distinguish between syntax and semantics. Breaking
their current, misguided model of programming languages is a
first step for them towards gaining a deeper understanding.
So, `return' is a feature, not a bug. I guess, the remedy
for the course would be to provoke a discussion of the issue
of C's return versus Haskell's return before the exam.