Am Freitag, 17. Februar 2006 03:34 schrieb Sean Seefried:
Hey all,
If you're interested in an implementation of constructor classes (type classes which can take constructors as arguments; already implemented in Haskell) please see:
http://www.cse.unsw.edu.au/~sseefried/code.html
This should help understanding the paper by Mark P. Jones called "A system of constructor classes: overloading and implicit higher-order polymorphism" much easier.
The implementation not only infers the type but also prints out a trace of the derivation tree for the syntax directed rules.
Cheers,
Sean
p.s. If you find any bugs, please let me know.
Re bugs: 1. printGamma [] would print an unmotivated " }", as witnessed by typeInf [] term14. 2. the case unify (ConT c) (AppT t1 t2) is missing. 3. too many shadowed bindings, this is always dangerous, I believe 4. I'm not sure, the datatypes are appropriate; as far as I know, expressions have a type and not a kind, which is what the use of the same Var type for Type and Exp entails. I have only just glimpsed at Jones' paper, so I don't yet see, what this type inference algorithm (quite nice, btw) has to do with constructor classes. If I still don't after reading it, I'll come back to ask. Cheers, Daniel -- "In My Egotistical Opinion, most people's C programs should be indented six feet downward and covered with dirt." -- Blair P. Houghton