[Haskell-cafe] casting

[Thomas Conway]

Thanks Misha & Matthias.

I now get what's going on. The mention of the word "dictionary"
revealed it all. I've spent the last 7 years programming in C++, and
had dynamic_cast<> firmly fixed in my head. I totally forgot that
Fergus Henderson and I independently reinvented dictionary passing for
the implementation of Mercury circa 1995. :-)

I also realized that the concrete signatures from my actual
application don't quite satisfy the requirements anyway, and that the
problem evaporates when I get the signatures right.:-)

T.