New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

content/covariance-contravariance.md: Positive/negative position, Exercise 3 #13

Open

spearman opened this issue Oct 23, 2015 · 1 comment

spearman commented Oct 23, 2015

Are the types supposed to be IO () rather than () here?

newtype E1 a = E1 (a -> ())
newtype E2 a = E2 (a -> () -> ())
newtype E3 a = E3 ((a -> ()) -> ())
newtype E4 a = E4 ((a -> () -> ()) -> ())
newtype E5 a = E5 ((() -> () -> a) -> ())

-- trickier:
newtype E6 a = E6 ((() -> a -> a) -> ())
newtype E7 a = E7 ((() -> () -> a) -> a)
newtype E8 a = E8 ((() -> a -> ()) -> a)
newtype E9 a = E8 ((() -> () -> ()) -> ())

The text was updated successfully, but these errors were encountered:

Contributor

snoyberg commented Oct 23, 2015

No, this was the intended type. It's meant to be irrelevant what the other type is, the focus is on a.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment