On 22 Dec 2008, at 15:18, Andrew Wagner wrote:
Yes, of course, sorry for the typo. On Mon, Dec 22, 2008 at 9:17 AM, Denis Bueno <[email protected]> wrote: 2008/12/22 Andrew Wagner <[email protected]>: > The problem here is even slightly deeper than you might realize. For> example, what if you have a list of functions. How do you compare two > functions to each other to see if they're equal? There is no good way really > to do it! So, not only is == not completely polymorphic, but it CAN'T be.> > There is a nice solution for this, however, and it's very simple: > > contain :: Eq a -> [a] -> Bool Please note that the syntax here should be: contain :: Eq a => a -> [a] -> Bool Denis
Of note, unless this is an exercise, such a function already exists -- it's called elem.
How do you find such a function? You search on haskell.org/hoogle. http://haskell.org/hoogle/?hoogle=Eq+a+%3D%3E+a+-%3E+%5Ba%5D+-%3E+Bool Bob
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