ajb@spamcop.net wrote in article <20070906064921.86dtrwt0v4go4s08@webmail.spamcop.net> in gmane.comp.lang.haskell.cafe:
That higher-rank type makes all the difference.
Yes. You can even do this portably, using nothing "unsafe", with Dylan Thurston's technique: Oleg Kiselyov and Chung-chieh Shan. 2004. Functional pearl: Implicit configurations -- or, type classes reflect the value of types. In Proceedings of the 2004 Haskell workshop, 33-44. New York: ACM Press. http://www.cs.rutgers.edu/~ccshan/prepose/ -- Edit this signature at http://www.digitas.harvard.edu/cgi-bin/ken/sig We're not "teaching Scheme." I spend about an hour teaching Scheme, and for the rest of the semester I /use/ Scheme to teach /computer science/. Brian Harvey (UC Berkeley) on comp.lang.scheme. Aug 22, 2007.