Search Results

Search found 7902 results on 317 pages for 'haskell platform'.

Page 6/317 | < Previous Page | 2 3 4 5 6 7 8 9 10 11 12 13  | Next Page >

  • Fork to shell script and terminate original process with Haskell

    - by Neth
    I am currently writing a Haskell program that does some initialization work and then calls ncmpcpp. What I am trying to do is start ncmpcpp and terminate the Haskell program, so that only ncmpcpp is left (optionally, the program can keep running in the background, as long as it's unintrusive) However, even though I am able to start ncmpcpp, I cannot interact with it. I see its output, but input appears to be impossible. What I am currently doing is: import System.Process (createProcess, proc) ... spawnCurses :: [String] -> IO () spawnCurses params = do _ <- createProcess (proc "ncmpcpp" params) return () What am I doing wrong/What should I do differently?

    Read the article

  • Why is there "data" and "newtype" in Haskell?

    - by martingw
    To me it seems that a newtype definition is just a data definition that obeys some restrictions (only one constructor and such), and that due to these restrictions the runtime system can handle newtypes more efficiently. Ok, and the handling of pattern matching for undefined values is slightly different. But suppose Haskell would only knew data definitions, no newtypes: Couldn't the compiler find out for himself whether a given data definition obeys these restrictions, and automatically treat it more efficiently? I'm sure I'm missing out on something, these Haskell designers are so clever, there must be some deeper reason for this...

    Read the article

  • The Oracle Platform

    - by Naresh Persaud
    Today’s enterprises typically create identity management infrastructures using ad-hoc, multiple point solutions. Relying on point solutions introduces complexity and high cost of ownership leading many organizations to rethink this approach. In a recent worldwide study of 160 companies conducted by Aberdeen Research, there was a discernible shift in this trend as businesses are now looking to move away from the point solution approach from multiple vendors and adopt an integrated platform approach. By deploying a comprehensive identity and access management strategy using a single platform, companies are saving as much as 48% in IT costs, while reducing audit deficiencies by nearly 35%. According to Aberdeen's research, choosing an integrated suite or “platform” of solutions for Identity Management from a single vendor can have many advantages over choosing “point solutions” from multiple vendors. The Oracle Identity Management Platform is uniquely designed to offer several compelling benefits to our customers.  Shared Services: Instead of separate solutions for - Administration, Authentication, Authorization, Audit and so on–  Oracle Identity Management offers a set of share services that allows these services to be consumed by each component in the stack and by developers of new applications  Actionable Intelligence: The most compelling benefit of the Oracle platform is ” Actionable intelligence” which means if there is a compliance violation, the same platform can fix it. And If a user is logging in from an un-trusted device or we detect an attack and act proactively on that information. Suite Interoperability: With the oracle platform the components all connect and integrated with each other. So if an organization purchase the platform for provisioning and wants to manage access, then the same platform can offer access management which leads to cost savings. Extensible and Configurable: With point solutions – you typically get limited ability to extend the tool to address custom requirements. But with the Oracle platform all of the components have a common way to extend the UI and behavior Find out more about the Oracle Platform approach in this presentation. Platform approach-series-the oracleplatform-final View more PowerPoint from OracleIDM

    Read the article

  • haskell: a data structure for storing ascending integers with a very fast lookup

    - by valya
    Hello! (This question is related to my previous question, or rather to my answer to it.) I want to store all qubes of natural numbers in a structure and look up specific integers to see if they are perfect cubes. For example, cubes = map (\x -> x*x*x) [1..] is_cube n = n == (head $ dropWhile (<n) cubes) It is much faster than calculating the cube root, but It has complexity of O(n^(1/3)) (am I right?). I think, using a more complex data structure would be better. For example, in C I could store a length of an already generated array (not list - for faster indexing) and do a binary search. It would be O(log n) with lower ?oefficient than in another answer to that question. The problem is, I can't express it in Haskell (and I don't think I should). Or I can use a hash function (like mod). But I think it would be much more memory consuming to have several lists (or a list of lists), and it won't lower the complexity of lookup (still O(n^(1/3))), only a coefficient. I thought about a kind of a tree, but without any clever ideas (sadly I've never studied CS). I think, the fact that all integers are ascending will make my tree ill-balanced for lookups. And I'm pretty sure this fact about ascending integers can be a great advantage for lookups, but I don't know how to use it properly (see my first solution which I can't express in Haskell).

    Read the article

  • Is there a trend for cross-platform GUI toolkits?

    - by Anto
    What is the trend like for the usage of cross-platform GUI frameworks right now? Are more people starting to use cross-platform frameworks (such as GTK+, Qt and wxWidgets) or are there more who use more platform-tied frameworks (e.g. Cocoa or WPF)? Is it more or less stagnant? Is it like a rollercoaster? What do you think the trend will be like, say, 5 years from now? The OS landscape is shifting with less people using Windows (personal observation). This should increase the demand for cross-platform toolkits, shouldn't it? Edit: Also, which (cross-platform) toolkits are growing the most, if so?

    Read the article

  • New projects not built when target platform is set explicitly

    - by stiank81
    I create a new solution with one project, and then change the target platform from "Any CPU" to "x86". After this new projects added doesn't get built by default, and their target platform doesn't follow the global settings. Why?! Looking at the configuration manager new projects added are not checked to "Build", and they get target platform "Any CPU" instead of the globally set x86. Why is this happening? I expect new projects too to get the globally set and defined x86 target platform.. Some things I've tried: Toggle global platform back to Any CPU, and then to x86 again. No change.. Choosing platform explicitly for the new project. x86 is not available in the list, and when I say <New..> and try adding it I'm not allowed as ".. a solution platform with the same name already exists.". On the build properties for the new project I can't change the platform in the Configuration section, but I can set "Platform target" to x86 in the General section. It is however not clear whether this actually makes a difference, and it wouldn't respond if I change the target platform globally later. Initially I thought this was a problem from converting my solution from VS2008 to VS2010, but the problem applies both places. I.e. when I create a solution in VS2008 and just stay in VS2008 I still get the problem.

    Read the article

  • Using Haskell's Parsec to parse binary files?

    - by me2
    Parsec is designed to parse textual information, but it occurs to me that Parsec could also be suitable to do binary file format parsing for complex formats that involve conditional segments, out-of-order segments, etc. Is there an ability to do this or a similar, alternative package that does this? If not, what is the best way in Haskell to parse binary file formats?

    Read the article

  • Turtle Graphics as a Haskell Monad

    - by iliis
    I'm trying to implement turtle graphis in Haskell. The goal is to be able to write a function like this: draw_something = do fordward 100 right 90 forward 100 ... and then have it produce a list of points (maybe with additional properties): > draw_something (0,0) 0 -- start at (0,0) facing east (0 degrees) [(0,0), (0,100), (-100,100), ...] I have all this working in a 'normal' way, but I fail to implement it as a Haskell Monad and use the do-notation. The basic code: data State a = State (a, a) a -- (x,y), angle deriving (Show, Eq) initstate :: State Float initstate = State (0.0,0.0) 0.0 -- constrain angles to 0 to 2*pi fmod :: Float -> Float fmod a | a >= 2*pi = fmod (a-2*pi) | a < 0 = fmod (a+2*pi) | otherwise = a forward :: Float -> State Float -> [State Float] forward d (State (x,y) angle) = [State (x + d * (sin angle), y + d * (cos angle)) angle] right :: Float -> State Float -> [State Float] right d (State pos angle) = [State pos (fmod (angle+d))] bind :: [State a] -> (State a -> [State a]) -> [State a] bind xs f = xs ++ (f (head $ reverse xs)) ret :: State a -> [State a] ret x = [x] With this I can now write > [initstate] `bind` (forward 100) `bind` (right (pi/2)) `bind` (forward 100) [State (0.0,0.0) 0.0,State (0.0,100.0) 0.0,State (0.0,100.0) 1.5707964,State (100.0,99.99999) 1.5707964] And get the expected result. However I fail to implement this as an instance of Monad. instance Monad [State] where ... results in `State' is not applied to enough type arguments Expected kind `*', but `State' has kind `* -> *' In the instance declaration for `Monad [State]' And if I wrap the list in a new object data StateList a = StateList [State a] instance Monad StateList where return x = StateList [x] I get Couldn't match type `a' with `State a' `a' is a rigid type variable bound by the type signature for return :: a -> StateList a at logo.hs:38:9 In the expression: x In the first argument of `StateList', namely `[x]' In the expression: StateList [x] I tried various other versions but I never got it to run as I'd like to. What am I doing wrong? What do I understand incorrectly?

    Read the article

  • optional arguments in haskell

    - by snorlaks
    Hello, I have declared my own type: data Book = Bookinfo { bookId :: Int, title :: String } deriving(Show) and now: x = Bookinfo it is all ok, valid statement but making bookId x throws an error. If I would be able to handle errors in Haskell that would be ok but right now I cant do this So Im curious how to make not specified values of fields take default value, and what exactly value is there when I'm not giving vcalues of fields in construcotr ? thanks for help

    Read the article

  • What does the >> symbol mean in Haskell.

    - by CharlesS
    I was reading the Guestbook example for Happstack and noticed the symbol which I didn't see before in the textbooks I studied to learn Haskell (for instance see line 23). What is it? Example I could not find it in Google because it ignores the totally (Bing does not but comes up with tons of non-related results). Thanks!

    Read the article

  • Simple haskell string manage

    - by paurullan
    Theres is a little problem I want to solve with Haskell: let substitute a function that change all of the wildcards in a string for one concrete parameter. The function has de signature of: subs :: String -> String -> String -> String -- example: -- subs 'x' "x^3 + x + sin(x)" "6.2" will generate -- "6.2^3 + 6.2 + sin(6.2)"

    Read the article

  • Creating Haskell instance declarations

    - by btl
    Hello, complete noob to Haskell here with probably an even noobier question. I'm trying to get ghci output working and am stuck on instance declarations. How could I declare an instance for "(Show (Stack - Stack))" given: data Cmd = LD Int | ADD | MULT | DUP deriving Show type Prog = [Cmd] type Stack = [Int] type D = Stack -> Stack I've been trying to create a declaration like: instance Show D where show = Stack but all my attempts have resulted in illegal instance declarations. Any help and/or references much appreciated!

    Read the article

  • Performance of looping over an Unboxed array in Haskell

    - by Joey Adams
    First of all, it's great. However, I came across a situation where my benchmarks turned up weird results. I am new to Haskell, and this is first time I've gotten my hands dirty with mutable arrays and Monads. The code below is based on this example. I wrote a generic monadic for function that takes numbers and a step function rather than a range (like forM_ does). I compared using my generic for function (Loop A) against embedding an equivalent recursive function (Loop B). Having Loop A is noticeably faster than having Loop B. Weirder, having both Loop A and B together is faster than having Loop B by itself (but slightly slower than Loop A by itself). Some possible explanations I can think of for the discrepancies. Note that these are just guesses: Something I haven't learned yet about how Haskell extracts results from monadic functions. Loop B faults the array in a less cache efficient manner than Loop A. Why? I made a dumb mistake; Loop A and Loop B are actually different. Note that in all 3 cases of having either or both Loop A and Loop B, the program produces the same output. Here is the code. I tested it with ghc -O2 for.hs using GHC version 6.10.4 . import Control.Monad import Control.Monad.ST import Data.Array.IArray import Data.Array.MArray import Data.Array.ST import Data.Array.Unboxed for :: (Num a, Ord a, Monad m) => a -> a -> (a -> a) -> (a -> m b) -> m () for start end step f = loop start where loop i | i <= end = do f i loop (step i) | otherwise = return () primesToNA :: Int -> UArray Int Bool primesToNA n = runSTUArray $ do a <- newArray (2,n) True :: ST s (STUArray s Int Bool) let sr = floor . (sqrt::Double->Double) . fromIntegral $ n+1 -- Loop A for 4 n (+ 2) $ \j -> writeArray a j False -- Loop B let f i | i <= n = do writeArray a i False f (i+2) | otherwise = return () in f 4 forM_ [3,5..sr] $ \i -> do si <- readArray a i when si $ forM_ [i*i,i*i+i+i..n] $ \j -> writeArray a j False return a primesTo :: Int -> [Int] primesTo n = [i | (i,p) <- assocs . primesToNA $ n, p] main = print $ primesTo 30000000

    Read the article

  • Understanding Haskell's filter

    - by dmindreader
    I understand that Haskell's filter is a high order function (meaning a function that takes another function as a parameter) that goes through a list checking which element fulfills certain boolean condition. I don't quite understand its definition: filter:: (a->Bool)->[a]->[a] filter p [] = [] filter p (x:y) | p x = x:filter p y | otherwise = filter p y I understand that if I pass an empty list to the function, it would just return an empty list, but how do I read the last two lines?

    Read the article

  • Control statements in Haskell?

    - by Nathan
    I am just beginning Haskell, but from all the online tutorials I've found I can't seem to find if there is one accepted way to do a conditional control statement. I have seen if-else, guards, and pattern matching, but they all seem to accomplish the same thing. Is there one generally accepted/faster/more efficient way than the rest?

    Read the article

  • Good Haskell coding standards

    - by Alexey Romanov
    Could someone provide a link to a good coding standard for Haskell? I've found this and this, but they are far from comprehensive. Not to mention that the HaskellWiki one includes such "gems" as "use classes with care" and "defining symbolic infix identifiers should be left to library writers only."

    Read the article

  • Why won't the following haskell code compile?

    - by voxcogitatio
    I'm in the process of writing a small lisp interpreter in haskell. In the process i defined this datatype, to get a less typed number; data Number = _Int Integer | _Rational Rational | _Float Double deriving(Eq,Show) Compiling this fails with the following error: ERROR "types.hs":16 - Syntax error in data type declaration (unexpected `|') Line 16 is the line w. the first '|' in the code above.

    Read the article

< Previous Page | 2 3 4 5 6 7 8 9 10 11 12 13  | Next Page >