-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Thanks Erik. This made the issue clear to me.
Best regards, Florian On 09/14/2012 03:22 PM, Erik Hesselink wrote: > On Fri, Sep 14, 2012 at 2:27 PM, Erik Hesselink > <hessel...@gmail.com> wrote: >> In general, I think you have to work inside an existential. So >> you hide the type of the parsed Term inside an existential. If >> you want to apply functions to this Term, you unpack, call the >> function, and repack. > > Maybe I should expand what I mean by this. Let's say you have: > > data SomeTerm where SomeTerm :: Term a -> SomeTerm > > Your typecheck function goes: > > typecheck :: Exp -> SomeTerm > > and you want to apply: > > transform :: Term t -> Term t > > You should do something like: > > f (SomeTerm t) = SomeTerm (transform t) > > Or, more generally: > > onSomeTerm :: (forall t. Term t -> Term t) -> SomeTerm -> SomeTerm > onSomeTerm f (SomeTerm t) = SomeTerm (f t) > > Erik > - -- Florian Lorenzen Technische Universität Berlin Fakultät IV - Elektrotechnik und Informatik Übersetzerbau und Programmiersprachen Sekr. TEL12-2, Ernst-Reuter-Platz 7, D-10587 Berlin Tel.: +49 (30) 314-24618 E-Mail: florian.loren...@tu-berlin.de WWW: http://www.user.tu-berlin.de/florenz/ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://www.enigmail.net/ iEYEARECAAYFAlBW2bgACgkQvjzICpVvX7Zr3QCfbIqkX9WqM69NLyk98aqyNcYe RrUAniGndhj9OTl9XIoUBC/hoBI1lwML =hReY -----END PGP SIGNATURE----- _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
