Re: [Haskell-cafe] How to declare a Typeless Function
On Fri, Jul 3, 2009 at 4:43 AM, Alexander Dunlapalexander.dun...@gmail.com 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 Bolandofernanbola...@mailc.net 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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Magnus Therning(OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus＠therning．org http://therning.org/magnus identi.ca|twitter: magthe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to declare a Typeless Function
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 Dunlapalexander.dun...@gmail.com 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 Bolandofernanbola...@mailc.net 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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe begin:vcard fn:Joseph Fredette n:Fredette;Joseph adr:Apartment #3;;6 Dean Street;Worcester;Massachusetts;01609;United States of America email;internet:jfred...@gmail.com tel;home:1-508-966-9889 tel;cell:1-508-254-9901 x-mozilla-html:FALSE url:lowlymath.net, humbuggery.net version:2.1 end:vcard ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] How to declare a Typeless Function
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
Re: [Haskell-cafe] How to declare a Typeless Function
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. Alex On Thu, Jul 2, 2009 at 8:05 PM, Fernan Bolandofernanbola...@mailc.net 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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
