Re: [Haskell-cafe] Int vs Integer?
Int is the type of machine integers, with guaranteed range at least -2^29 to 2^29 - 1, while Integer is arbitrary precision integers, with range as large as you have memory for. The code you gave, on its own, is fine. The types inferred by ghci are ints :: [Int] and prng :: [[Int]] Hugs seems to choke on it though. If you provide an explicit type signature for ints, it works fine. It seems to be defaulting the type to [Integer] a little too early. I expect you'll replace ints with a more interesting list, as ints !! i is currently equal to i. If you need to coerce something of integral (Int, Integer) type to any numeric type, use fromIntegral. hope this helps, - Cale On 5/5/05, Daniel Carrera [EMAIL PROTECTED] wrote: Hello, What's the difference between Int and Integer? How can I tell Haskell which one I want? I'm having trouble with a function: ints = 0 : map (1+) ints prng = map iter ints where iter 0 = [0,0] iter n = [i,j] where i = mod n 256 j = ints !! i (eventually 'iter' will be more a more interesting function). When I try to load this module in Hugs I get the error: ERROR ./PRNG.hs:24 - Type error in list *** Expression : [i,j] *** Term : j *** Type : Integer *** Does not match : Int Line 24 is the 'prng' line. I've spent all day trying to fix this, but for the life of me I can't figure out why it happens or how to make it stop. Haskell just doesn't seem to like the 'iter !! i' construct. It's interesting that if you replace 'i' by (say) 3, Haskell runs the program happily. But, if you replace 'i = mod n 256' by 'i=3' you get the same error. Any words of wisdom would be appreciated. Cheers, Daniel. ___ 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
[Haskell-cafe] How to show a variable with show?
Hi! In my program I would like to see an result of function or an variable. Wenn I use show myfunction or show variable, I'm getting errors like ERROR - Improperly terminated character constant or Syntax error in declaration (unexpected `;', possibly due to bad layout) Any help would be appreciated! Yahoo! Mail Stay connected, organized, and protected. Take the tour: http://tour.mail.yahoo.com/mailtour.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell vs OCaml
On Wed, 2005-05-04 at 18:29 -0400, Jacques Carette wrote: There is also Template Haskell vs MetaOCaml. For the life of me, I still cannot fathom why Template Haskell is untyped, while MetaOCaml is fully typed. Which is the main reason I write meta-program in MetaOCaml and 'other' programs in Haskell. The reason for this is that Template Haskell is more powerful and correspondingly harder to type so it is currently untyped. The main reason it is more porwerful is that TH allows you to pattern match on the abstract syntax of a quoted expression and perform arbitrary transformations on that. It would be hard to preserve the well-typedness of the AST and still allow arbitrary transformations. A colleague of mine is currently developing a type system for Template Haskell that should catch most errors without restricting too much the programs you can write. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] NumberTheory library
You might want to check out the archives of the mailing list, too. These sorts of problems occasionally get solved. For the record, here are a few of my attempts: http://andrew.bromage.org/Fib.hs (Fairly fast Fibonacci numbers) http://andrew.bromage.org/WheelPrime.hs (Fast factorisation) http://andrew.bromage.org/Prime.hs (AKS primality testing) Great, why not put these together in a first attempt of making a standard library? Or is the road to creating standard libraries starting somewhere else? I actually dont know. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to show a variable with show?
Hi module Main where main = do putStr (show (foo 3)) putStr \n putStr (show (foo 7)) putStr \n putStr (show y) foo x = (x + 2) / y where y = 2 * 2 And how do I see functions or variables defined inside of other functions? In example above - y Short answer -- you don't. Haskell is a purely functional langauge and functions can therefore not have side effects. Side effects can only occur in the IO monad (and maybe in some other monads) as shown above in main, which really is a IO monad with type main :: IO(). Therefore you cannot print the value of y to the screen in the middle of the foo function. This may seem like a stupid limitation, but restricting your functions to be pure eliminates a lot of errors. And in my, albeit limited Haskell experience, there is rarely a need to see the value of variables writen inside other funcitons (as shown in your example). If you really need this kind of feedback, then there are some debugging tools here: http://www.haskell.org/libraries/#tracing which may do it for you. However, I have tried none of them and do not really know what they can do. hope it helps, Mads Lindstrøm [EMAIL PROTECTED] Yahoo! Mail Stay connected, organized, and protected. Take the tour: http://tour.mail.yahoo.com/mailtour.html ___ 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
Re: [Haskell-cafe] How to show a variable with show?
And how do I see functions or variables defined inside of other functions? In example above - y Short answer -- you don't. Thanks for explanations! Cheers, M. __ Do you Yahoo!? Yahoo! Mail - Helps protect you from nasty viruses. http://promotions.yahoo.com/new_mail ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell vs OCaml
Duncan Coutts wrote: On Wed, 2005-05-04 at 18:29 -0400, Jacques Carette wrote: There is also Template Haskell vs MetaOCaml. For the life of me, I still cannot fathom why Template Haskell is untyped, while MetaOCaml is fully typed. Which is the main reason I write meta-program in MetaOCaml and 'other' programs in Haskell. The reason for this is that Template Haskell is more powerful and correspondingly harder to type so it is currently untyped. ``more powerful'' meaning that it can do some level of introspection, right? I know introspection can be very powerful (I designed Maple's modern reflection and reification facilities...), but I was under the impression that type systems that can handle 'too much' introspection were unsound [a result of Walid Taha]. The main reason it is more porwerful is that TH allows you to pattern match on the abstract syntax of a quoted _expression_ and perform arbitrary transformations on that. It would be hard to preserve the well-typedness of the AST and still allow arbitrary transformations. Can't this be regarded as a 'convenience' rather than as actual extra power? Using an abstract interpretation formalism (see papers of Taha and co-authors), it is possible to 'lift' the type of code values into staging-time terms, and pattern-match on that instead. Then well-typedness of transformations is much easier to show. In this way one can even implement some transformations that are equivalent to what are currently 'hints' to GHC as well-typed code [I have some code that does this, but there are only hints of this in a preprint of mine -- see the conclusion section of "Gaussian Elimination: a case study in efficient genericity with MetaOCaml" available from http://www.cas.mcmaster.ca/~carette/publications.html for some hints on how this is done A colleague of mine is currently developing a type system for Template Haskell that should catch most errors without restricting too much the programs you can write. I am eagerly awaiting this! Writing Monadic meta-programs in MetaOCaml is feasible, but the lack of native support for Monads makes it significantly harder. But after spending 12 years writing programs in a fully dynamically typed language (Maple), I am much happier writing all parts of my programs in a strongly typed language! Jacques ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Conal Elliott's Vertigo, anyone get it to run?
On 5/5/05, Atwood, John Wesley [EMAIL PROTECTED] wrote: I tried to run Conal Elliott's Vertigo demos, on 3 diffferent XP boxes; it ran on none. The error is Common Language Runtime Services - Appication has generated an exception that could not be handled. Process id=, Thread id=. Any suggestions? http://conal.net/Vertigo/ On 5/5/05, Sebastian Sylvan [mailto:[EMAIL PROTECTED] wrote: Do you have .Net installed? I got it to run, don't know what you're doing wrong. Yep, version 1.1; don't have the C# compiler installed, but it's my understanding that that's not needed for the demos. John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Squashing space leaks
Josef Svenningsson wrote: I think the thing that really kills you is the way you shuffle around the list in the advance function. Your commented out rotations function has the same problem. Here is my attempt to solve the problem a little more efficiently: We're heading in the right direction anyway. I can now compute 1 million iteration in about 2 minutes (with +RTS -H750M -K100M). Well almost, since it now doesn't compute the right answer, so something must be amiss in the shuffling section. Now if we can get it to us a little less than 1G of memory, we'll be in good shape. Thanks, Greg Buchholz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
