Hello, Data.Typeable gives you most of what you want except for access to function bodies.
-Jeff On Tue, Mar 11, 2008 at 6:17 AM, Martin Hofmann <[EMAIL PROTECTED]> wrote: > I am trying to port a programme written in Maude, which is a reflective > language based on rewriting logic ( http://maude.cs.uiuc.edu/ ), to > Haskell. I thought using Template Haskell might be a good idea, but I > got stuck and now I am wondering if this is really possible in Haskell. > Let me give an example of a Maude module defining the function last over > a list of Peano numbers. > > fmod LAST is > sorts Peano PeanoList . > > op 0 : -> Peano [ctor] . > op s : Peano -> Peano [ctor] . > > op [] : -> PeanoList [ctor] . > op cons : Peano PeanoList -> PeanoList [ctor] . > > op last : PeanoList -> Peano . > > vars X Y : Peano . > var Xs : PeanoList . > > eq last(cons(X,[])) = X . > eq last(cons(X,cons(Y,Xs))) = last(cons(Y,Xs)) . > > endfm > > So, last(cons(s(0),cons(s(s(0)),cons(s(s(s(0))),[])))) would reduce to > s(s(s(0))). The cool thing about Maude is, that terms, modules, ... can > be lifted to the meta level. For example: > > upModule('LAST, false) > > would yield > > fmod 'LAST is > including 'BOOL . > sorts 'Peano ; 'PeanoList . > none > op '0 : nil -> 'Peano [ctor] . > op '`[`] : nil -> 'PeanoList [ctor] . > op 'cons : 'Peano 'PeanoList -> 'PeanoList [ctor] . > op 'last : 'PeanoList -> 'Peano [none] . > op 's : 'Peano -> 'Peano [ctor] . > none > eq 'last['cons['X:Peano,'`[`].PeanoList]] = 'X:Peano [none] . > eq 'last['cons['X:Peano,'cons['Y:Peano,'Xs:PeanoList]]] = > last['cons[ 'Y:Peano,'Xs:PeanoList]] [none] . > endfm > > I also have access, e.g. to the defined type constructors. > > So > upOpDecls('LAST,false). > > yields > > op '0 : nil -> 'Peano [ctor] . > op '`[`] : nil -> 'PeanoList [ctor] . > op 'cons : 'Peano 'PeanoList -> 'PeanoList [ctor] . > op 'last : 'PeanoList -> 'Peano [none] . > op 's : 'Peano -> 'Peano [ctor] . > > Given an arbitrary function, I have access to its definition, its types > and the type constructors, all as ADTs. > > Is this possible with Template Haskell, or in some other way? > > Thanks a lot, > > Martin > > > > > > > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
