It's important to note that such a function is not "Typeless" but rather "Polymorphic" -- that is, it is a type which can be satisfied for many values of it's type variables. For instance, the function `(+) :: Num a => a -> a -> a` is polymorphic, since it's one type variable can be satisfied by any instance of the `Num` class. It's not that the `(+)` function is "Typeless" (implying that it has no type) precisely the opposite, it has _many_ types. Haskell is clever enough to figure out which one you mean as you use it (most of the time, anyway). /Joe Magnus Therning wrote:

On Fri, Jul 3, 2009 at 4:43 AM, Alexander Dunlap wrote:

...

swap :: Array (Int, Int) a -> [Int] -> Array (Int, Int) a

The lowercase "a" means that that type variable is polymorphic, i.e. it can be any type.

Another option would be to simply not put in type of 'swap', load it in ghci and see what the compiler says the type is :-)

/M

...

On Thu, Jul 2, 2009 at 8:05 PM, Fernan Bolando wrote:

...

Hi

I have a function that swaps rows of an array of double

swap :: Array (Int,Int) Double -> [Int] -> Array (Int,Int) Double

I then create a function that swaps rows of arrays of Complex Double

swap :: Array (Int, Int) (Complex Double) -> [Int] -> Array (Int, Int) (Complex Double)

In reality the function swap does not care whether its working on a double or a complex number. how do I declare swap so that it will work whether it's a complex or a double array.

I tried googling but I wasn't sure what to google.

fernan -- http://www.fernski.com _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

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