[Haskell-cafe] Data structure containing elements which are instances of the same type class

Albert Y. C. Lai trebla at vex.net
Wed Aug 15 20:55:59 CEST 2012

On 12-08-15 03:20 AM, wren ng thornton wrote:
>      (forall a. P(a)) -> Q  <=>  exists a. (P(a) -> Q)

For example:

A. (forall p. p drinks) -> (everyone drinks)
B. exists p. ((p drinks) -> (everyone drinks))

In a recent poll, 100% of respondents think A true, 90% of them think B 
paradoxical, and 40% of them have not heard of the Smullyan drinking 



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