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  • functional dependencies vs type families

    - by mhwombat
    I'm developing a framework for running experiments with artificial life, and I'm trying to use type families instead of functional dependencies. Type families seems to be the preferred approach among Haskellers, but I've run into a situation where functional dependencies seem like a better fit. Am I missing a trick? Here's the design using type families. (This code compiles OK.) {-# LANGUAGE TypeFamilies, FlexibleContexts #-} import Control.Monad.State (StateT) class Agent a where agentId :: a -> String liveALittle :: Universe u => a -> StateT u IO a -- plus other functions class Universe u where type MyAgent u :: * withAgent :: (MyAgent u -> StateT u IO (MyAgent u)) -> String -> StateT u IO () -- plus other functions data SimpleUniverse = SimpleUniverse { mainDir :: FilePath -- plus other fields } defaultWithAgent :: (MyAgent u -> StateT u IO (MyAgent u)) -> String -> StateT u IO () defaultWithAgent = undefined -- stub -- plus default implementations for other functions -- -- In order to use my framework, the user will need to create a typeclass -- that implements the Agent class... -- data Bug = Bug String deriving (Show, Eq) instance Agent Bug where agentId (Bug s) = s liveALittle bug = return bug -- stub -- -- .. and they'll also need to make SimpleUniverse an instance of Universe -- for their agent type. -- instance Universe SimpleUniverse where type MyAgent SimpleUniverse = Bug withAgent = defaultWithAgent -- boilerplate -- plus similar boilerplate for other functions Is there a way to avoid forcing my users to write those last two lines of boilerplate? Compare with the version using fundeps, below, which seems to make things simpler for my users. (The use of UndecideableInstances may be a red flag.) (This code also compiles OK.) {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances, UndecidableInstances #-} import Control.Monad.State (StateT) class Agent a where agentId :: a -> String liveALittle :: Universe u a => a -> StateT u IO a -- plus other functions class Universe u a | u -> a where withAgent :: Agent a => (a -> StateT u IO a) -> String -> StateT u IO () -- plus other functions data SimpleUniverse = SimpleUniverse { mainDir :: FilePath -- plus other fields } instance Universe SimpleUniverse a where withAgent = undefined -- stub -- plus implementations for other functions -- -- In order to use my framework, the user will need to create a typeclass -- that implements the Agent class... -- data Bug = Bug String deriving (Show, Eq) instance Agent Bug where agentId (Bug s) = s liveALittle bug = return bug -- stub -- -- And now my users only have to write stuff like... -- u :: SimpleUniverse u = SimpleUniverse "mydir"

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  • Drawing path by Bezier curves

    - by OgreSwamp
    Hello. I have a task - draw smooth curve input: set of points (they added in realtime) current solution: I use each 4 points to draw qubic Bezier curve (1 - strart, 2 and 3rd - control points, 4- end). End point of each curve is start point for the next one. problem: at the curves connection I often have "fracture" (angle) Can you tell me, how to connect my points more smooth? Thanks!

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  • Hide public method used to help test a .NET assembly

    - by ChrisW
    I have a .NET assembly, to be released. Its release build includes: A public, documented API of methods which people are supposed to use A public but undocumented API of other methods, which exist only in order to help test the assembly, and which people are not supposed to use The assembly to be released is a custom control, not an application. To regression-test it, I run it in a testing framework/application, which uses (in addition to the public/documented API) some advanced/undocumented methods which are exported from the control. For the public methods which I don't want people to use, I excluded them from the documentation using the <exclude> tag (supported by the Sandcastle Help File Builder), and the [EditorBrowsable] attribute, for example like this: /// <summary> /// Gets a <see cref="IEditorTransaction"/> instance, which helps /// to combine several DOM edits into a single transaction, which /// can be undone and redone as if they were a single, atomic operation. /// </summary> /// <returns>A <see cref="IEditorTransaction"/> instance.</returns> IEditorTransaction createEditorTransaction(); /// <exclude/> [EditorBrowsable(EditorBrowsableState.Never)] void debugDumpBlocks(TextWriter output); This successfully removes the method from the API documentation, and from Intellisense. However, if in a sample application program I right-click on an instance of the interface to see its definition in the metadata, I can still see the method, and the [EditorBrowsable] attribute as well, for example: // Summary: // Gets a ModelText.ModelDom.Nodes.IEditorTransaction instance, which helps // to combine several DOM edits into a single transaction, which can be undone // and redone as if they were a single, atomic operation. // // Returns: // A ModelText.ModelDom.Nodes.IEditorTransaction instance. IEditorTransaction createEditorTransaction(); // [EditorBrowsable(EditorBrowsableState.Never)] void debugDumpBlocks(TextWriter output); Questions: Is there a way to hide a public method, even from the meta data? If not then instead, for this scenario, would you recommend making the methods internal and using the InternalsVisibleTo attribute? Or would you recommend some other way, and if so what and why? Thank you.

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  • Commit in SVN without letting other to checkout - is it possible?

    - by strDisplayName
    Hey everybody, I am using SVN as my source control with ANKH and TortoiseSVN. I am writing a huge change in a project, and it takes a few days to make the change, but in the meantime I still want to commit once in a while for backup. But if I commit other team members will get updated with my unfinished work. Is there a way that I can "commit for backup" without changing the revision (so other won't get updated with my changes)? Thanks!

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  • Sending Mail using PHP on IIS 7 - Windows 2008 Server

    - by Roman
    Hi, I'm having trouble sending mail using PHP mail() on IIS 7 using Windows 2008 Server. The server is dedicated, thus I have full control over my machine. php.ini looks fine - ([mail function] is configured) I don't get any error from mail() (with the right parameters of course) btw - I got ASP and ASP.NET sending mails without any problems. Would be very gratefully for help Regards, Roman

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  • Embedding a Bitmap in ASP.NET's WebResource

    - by Andreas Grech
    I am generating a System.Drawing.Bitmap on the fly in an ASP.NET Custom Web Server Control, and then I want to serve this bitmap as part of the WebResource, because I do not want to save it on the hosting computer. Is there a way to instruct ASP.NET to serve the generated System.Drawing.Bitmap as part of it's WebResource? (therefore making it an "Embedded Resource")

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  • VB6 Serial port programming

    - by commodus86
    I'm not much experienced in VB6 serial port programming. I need to control another circuit through serial port. (I have heard that pin 4 and pin 7 are used for that purpose. If these pins are incorrect please tell me what pins are used for such purposes) My requirement is to set those pins to high or low and read their levels(high or low) through VB6 program. How to do the task?? Thanx,

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  • use pin.title in other class

    - by Marco
    Hello i have implemented the following code: - (void) mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)annView calloutAccessoryControlTapped:(UIControl *)control { name = annView.annotation.title; NSLog(name, [annView description]); } and how can I use the variable name in another class? can you please help me, i am new in iphone developing!

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  • C#: how to obtain the current clock speed of an Intel i-series CPU when TurboBoost is activated

    - by shifuimam
    I know that it's possible to get this information - Intel's own TurboBoost sidebar gadget appears to use an ActiveX control to determine the current clock speed of an i3/i5/i7 CPU when TurboBoost is active. However, I'm wanting to do this programmatically in C# - obtaining the CurrentClockSpeed value from WMI tops out at the set maximum clock speed of the CPU, so in TurboBoost mode, it doesn't report the current actual clock speed.

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  • What's the best way to tell if the mouse is over a form or not?

    - by cyclotis04
    I figured out how to capture mouse clicks over the entire form, but this method doesn't translate well for MouseEnter and MouseLeave. My form layout is made up from many Panels and TableLayoutPanels so there's no all-encompassing control I can monitor events for, and obviously a MouseLeave event for a button doesn't mean the cursor left the entire form. Has anyone figured out a good way to get around this?

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  • File Upload Validator always show error message

    - by Space Cracker
    i add asp.net file upload control as following <asp:FileUpload ID="filesFileUpload" runat="server" /> <asp:RegularExpressionValidator ID="RegularExpressionValidator3" runat="server" ErrorMessage="file types not supported" ValidationExpression="\.(zip.rar|jpg|gif|png|eps|ai|psd|pdf)$" ControlToValidate="filesFileUpload"></asp:RegularExpressionValidator> and always when i upload file that match the reg expression it show the error .. could any help me why this done ?

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  • asp.net login controls droped error "object expected" when i click the "administer website" to debug

    - by user306032
    hello: i have just created a new empty website from visualstudio 2010, added an new webform and droped a login control into the page.when i click the tag "administer website" then try to open security-Use the security Setup Wizard to configure security step by step, the IE8 shows the error: "Object Expected". (tried to make a asp.net site with generated code, without any modification, but the error still occered)script type="text/javascript"

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  • problem in letter's language.....

    - by mohammad
    Hello... I have a problem after i setup windows 7 all old projects in c# vs 2005, the letters that written in arabic changed to a strange language and i changed the language's settings in control panel to arabic then the new projects passed but the old projects have the same problem

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  • How do I format and apply rails methods to output of Ruport?

    - by Angela
    I am creating a report from Ruport and want to be able to take the grouping heading, in this case the ID for the class Email, and wrap a method around it and a link_to to link to the Email view based on the email_id: @table = ContactEmail.report_table(:all, :conditions => ['date_sent >= ? and date_sent <= ?', @monday, @friday]) @grouping = Grouping(@table, :by => "email_id") How do I do that? It feels as if I have little control over the output.

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  • Why do I need to commit ignores under TortoiseSVN?

    - by James McMahon
    When I select ignore on a files under version control it marks the parent directory as changes, then when I then do a commit, it checks in svn:ignore property to the repository, resulting in another revision. Why do I need to commit the svn:ignore property? Is this a TortoiseSVN issue or just the way SVN works?

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