Check Wikipedia. Peirce law, law of excluded middle, double negation, ...
they are all equivalent and it can be instructive to see how one can derive
one from the other.
On 10/17/07, Tim Newsham
Very clear tutorial indeed. But why isn't propCC shown as Pierce's Law? And Excluded middle is proven on such basis.
Simply because I don't know that much about pierce's law. I've seen it mentioned a few times, but I'm not that familiar with it yet and I haven't read a good treatment of it yet. Do you have any pointers to something I could read?
Vitaliy.
Tim Newsham http://www.thenewsh.com/~newsham/ _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe