Q3 Example Exam, Feb 24 2011

[Hugo]

Q3 for which the answer is

infer env (exp1 + exp2) =
typ := infer env exp1
check condition (typ == int || typ == double)
check env (exp2 : typ)
return typ


Are we here assuming an implicit Err-monad where each statement's
failure is taken care of? I mean, what if the type of exp1 cant be
inferred? Or else, what if the type of exp1 is neither int nor double?

The question says "the rule has to return a type". Maybe they meant it
should return a type as long as it doesnt return an error?

[Arnar Birgisson]

Hi,

Yes, in the answer implicit error handling is assumed. I.e. if either
of the check commands fail, the whole rule fails.

cheers,
Arnar