On Fri, Feb 08, 2008 at 06:47:51PM -0800, Ryan Ingram wrote: > I'm assuming you mean the rule described in > http://en.wikibooks.org/wiki/Formal_Logic/Sentential_Logic/Inference_Rules > > > type Disj a b = Either a b > > > disj_elim :: Disj a b -> (a -> c) -> (b -> c) -> c > > disj_elim (Left a) a2c b2c = a2c a > > disj_elim (Right b) a2c b2c = b2c b > > If you know "either a is true, or b is true" > and you know "from a, I can prove c", > and you know "from b, I can prove c", > then you can prove c.
aka: import Data.Either type Disj = Either disj_elim = either Stefan
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