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  • Avoiding explicit recursion in Haskell

    - by Travis Brown
    The following simple function applies a given monadic function iteratively until it hits a Nothing, at which point it returns the last non-Nothing value. It does what I need, and I understand how it works. lastJustM :: (Monad m) => (a -> m (Maybe a)) -> a -> m a lastJustM g x = g x >>= maybe (return x) (lastJustM g) As part of my self-education in Haskell I'm trying to avoid explicit recursion (or at least understand how to) whenever I can. It seems like there should be a simple non-explicitly recursive solution in this case, but I'm having trouble figuring it out. I don't want something like a monadic version of takeWhile, since it could be expensive to collect all the pre-Nothing values, and I don't care about them anyway. I checked Hoogle for the signature and nothing shows up. The m (Maybe a) bit makes me think a monad transformer might be useful here, but I don't really have the intuitions I'd need to come up with the details (yet). It's probably either embarrassingly easy to do this or embarrassingly easy to see why it can't or shouldn't be done, but this wouldn't be the first time I've used self-embarrassment as a pedagogical strategy. Background: Here's a simplified working example for context: suppose we're interested in random walks in the unit square, but we only care about points of exit. We have the following step function: randomStep :: (Floating a, Ord a, Random a) => a -> (a, a) -> State StdGen (Maybe (a, a)) randomStep s (x, y) = do (a, gen') <- randomR (0, 2 * pi) <$> get put gen' let (x', y') = (x + s * cos a, y + s * sin a) if x' < 0 || x' > 1 || y' < 0 || y' > 1 then return Nothing else return $ Just (x', y') Something like evalState (lastJustM (randomStep 0.01) (0.5, 0.5)) <$> newStdGen will give us a new data point.

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  • `DesignMode` in subcontrols is not set correctly?

    - by affan
    I have a compound control contains nested controls. The problem i am facing is that control read properties from a global setting class which is static and intern read from setting file. To stop individual control from accessing configuration in design mode i added check in each control. If(!DesignMode){ ... //Initialize properties e.g. prop = AppConfig.GetProperty("prop1"); } The problem is that individual control work fine when open in VS. But when i open top control containing nested control i get error by VS designer. The error is that in a nested control DesignMode=false for some reason. I also created a test app and created a simple control within another control to test if there is a problem with VS but it seem to work correctly for any depth of controls. I dont even know how to debug this. For now i comment out the property initializing code and build it and then open designer and there uncomment it and build it again to run it. Did anyone came across this problem or is there any way to fix it.

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  • Cant change text in custom cell

    - by darkman
    I created a custom cell to display a text a two images, when the user select the cell, the image is suposed to change, i can acess the properties of the cell, but cant change then : - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { [tableView deselectRowAtIndexPath:indexPath animated:YES]; CustomCell *cell = (CustomCell *)[self.tableView cellForRowAtIndexPath:indexPath]; cell.check.image = setImage:[UIImage imageNamed:@"1355327732_checkbox-checked"]; [cell.check setImage:[UIImage imageNamed:@"1355327732_checkbox-checked"]]; } cell.check is a UIImageView Am i missing something?

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  • Confused about NoMethodError in Ruby

    - by E L
    In a simple Ruby example, I'm getting an error that does not occur in irb. name = "Joe" def say_hi "\"Hi there!\" said #{self}" end response = name.say_hi puts response This code should return, "Hi there!" said Joe. It works perfectly fine in irb. However, when I attempt to put the same code in a file and run the file, I get this error: say_hi.rb:8:in `<main>': private method `say_hi' called for "Joe":String (NoMethodError) Any suggestion about why this happens?

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  • What are possible/good ways to prototype iPhone applications?

    - by Ted Johnson
    This is intentionally left broad. If you wanted to show users what iPhone/mobile applications could to for them. The more interactive the better, but it must be quick to build as you can't code up every idea. Let us assume real-time games are out of scope. Throw out ideas or state which approach would be best. Here are some of my ideas, what are yours? Hack a app that loads mostly web or image content, but has hyperlinks to get around in. This would mean static data. Build screens which look great but can only be navigated in a story board type fashion. Load the web version or equivalent on the iPhone and say: now image the buttons and navigation is better. A paper based prototype. Flash or video walk through running on the phone. String existing iPhone apps and web pages together with minimal glue just to convey the idea. Can anyone share prototyping methods for other mobile devices? Ex: The palm prototype was just a block of wood and note pad that was carried around.

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  • How do I enforce the order of qmake library dependencies?

    - by James Oltmans
    I'm getting a lot of errors because qmake is improperly ordering the boost libraries I'm using. Here's what .pro file looks like QT += core gui TARGET = MyTarget TEMPLATE = app CONFIG += no_keywords \ link_pkgconfig SOURCES += file1.cpp \ file2.cpp \ file3.cpp PKGCONFIG += my_package \ sqlite3 LIBS += -lsqlite3 \ -lboost_signals \ -lboost_date_time HEADERS += file1.h\ file2.h\ file3.h FORMS += mainwindow.ui RESOURCES += Resources/resources.qrc This produces the following command: g++ -Wl,-O1 -o MyTarget file1.o file2.o file3.o moc_mainwindow.o -L/usr/lib/x86_64-linux-gnu -lboost_signals -lboost_date_time -L/usr/local/lib -lmylib1 -lmylib2 -lsqlite3 -lQtGui -lQtCore Note: mylib1 and mylib2 are statically compiled by another project, placed in /usr/local/lib with an appropriate pkg-config .pc file pointing there. The .pro file references them via my_package in PKGCONFIG. The problem is not with pkg-config's output but with Qt's ordering. Here's the .pc file: prefix=/usr/local exec_prefix=${prefix} libdir=${exec_prefix}/lib includedir=${prefix}/include Name: my_package Description: My component package Version: 0.1 URL: http://example.com Libs: -L${libdir} -lmylib1 -lmylib2 Cflags: -I${includedir}/my_package/ The linking stage fails spectacularly as mylib1 and mylib2 come up with a lot of undefined references to boost libraries that both the app and mylib1 and mylib2 are using. We have another build method using scons and it properly orders things for the linker. It's build command order is below. g++ -o MyTarget file1.o file2.o file3.o moc_mainwindow.o -L/usr/local/lib -lmylib1 -lmylib2 -lsqlite3 -lboost_signals -lboost_date_time -lQtGui -lQtCore Note that the principle difference is the order of the boost libs. Scons puts them at the end just before QtGui and QtCore while qmake puts them first. The other differences in the compile commands are unimportant as I have hand modified the qmake produced make file and the simple reordering fixed the problem. So my question is, how do I enforce the right order in my .pro file despite what qmake thinks they should be?

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  • UIView animation problem

    - by FoJjen
    I try to make a UIImageView open like a hatch, and under the "hatchView" its anoter imageView but when I start the animation its like the view under gets over and cover the animation, When the animation gets over the imageView the its getting visibel. its works fine if a remove the imageView thats under. Here is the code for animation view. - (void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *) event { if (!isHatchOpen) { if (hatchView.layer.anchorPoint.x != 0.0f) { hatchView.layer.anchorPoint = CGPointMake(0.0f, 0.5f); hatchView.center = CGPointMake(hatchView.center.x - hatchView.bounds.size.width/2.0f, hatchView.center.y); } UITouch *touch = [touches anyObject]; CGPoint location = [touch locationInView:hatchView]; [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:1]; [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; [UIView setAnimationBeginsFromCurrentState:YES]; float pct = location.x / 320.0f; float rad = acosf(pct); CATransform3D transform = CATransform3DMakeRotation(-rad+5, 0.0f, -1.0f, 0.0f); transform.m14 = (1.0 / -2000) * acosf(pct); hatchView.layer.transform = transform; [UIView commitAnimations]; isHatchOpen = YES; } else { if (hatchView.layer.anchorPoint.x != 0.0f) { hatchView.layer.anchorPoint = CGPointMake(0.0f, 0.5f); hatchView.center = CGPointMake(hatchView.center.x - hatchView.bounds.size.width/2.0f, hatchView.center.y); } [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:1]; [UIView setAnimationCurve:UIViewAnimationCurveLinear]; [UIView setAnimationBeginsFromCurrentState:YES]; CATransform3D transform = CATransform3DMakeRotation(0, 0.0f, -1.0f, 0.0f); transform.m14 = 0; hatchView.layer.transform = transform; // Commit the changes [UIView commitAnimations]; isHatchOpen = NO; } } And here a add the Views hatchView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 1, frame.size.width-1, frame.size.height-2)]; [self addSubview:hatchView]; imageView = [[UIImageView alloc] initWithFrame:CGRectMake(1, 1, frame.size.width-2, frame.size.height-2)]; imageView.contentMode = UIViewContentModeScaleAspectFit; [self insertSubview:imageView belowSubview:hatchView];

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  • Getting a gestureoverlayview

    - by Codejoy
    I have been using some nice tutorials on drawing graphics on my android. I wanted to also add in the cool gesture demo found here: http://developer.android.com/resources/articles/gestures.html That takes these lines of code: GestureOverlayView gestures = (GestureOverlayView) findViewById(R.id.gestures); gestures.addOnGesturePerformedListener(this); This is fine and dandy yet I realize in my demo i'm trying to build using code from "Playing with Graphics in Android". The demos make sense, everything makes sense but I found out by using: setContentView(new Panel(this)); as is required by the Playing With Graphics tutorials, then the findViewById seems to no longer be valid and returns null. At first I was about to post a stupider question as to why this is happening, a quick test of playing with the setContentView made me realize the cause of findViewById returning null, I just do not know how to remedy this issue. Whats the key I am missing here? I realize that the new Panel is doinking some reference up but I am not sure how to make the connection here. The: R.id.gestures is defined right int he main.xml as: (just like the tutorial) <android.gesture.GestureOverlayView android:id="@+id/gestures" android:layout_width="fill_parent" android:layout_height="0dip" android:layout_weight="1.0" /> So I did confirm the setContentView(new Panel(this)) is causing the issue. So I know the issue is that I have to figure out how to add the android.gesture.GestureOverlayView to the panel class somehow, I am just not sure how to go about this. After fighting with this I generally know what I need to do just now how to do it. I think I need either the equivalent of creating a panel in that main.xml OR figuring out how to build whats in main.xml for the gestures in code. I am close because I did this: GestureOverlayView gestures = new GestureOverlayView(this); which gets me a non null gestures now, unfortunately since I am not telling it to fill Parent anywhere I don't think its really showing up, so I am trying hard to figure out layout pa rams. Am I even on the right track?

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  • Problems with validates_inclusion_of, acts_as_tree and rspec

    - by Jens Fahnenbruck
    I have problems to get rspec running properly to test validates_inclusion_of my migration looks like this: class CreateCategories < ActiveRecord::Migration def self.up create_table :categories do |t| t.string :name t.integer :parent_id t.timestamps end end def self.down drop_table :categories end end my model looks like this: class Category < ActiveRecord::Base acts_as_tree validates_presence_of :name validates_uniqueness_of :name validates_inclusion_of :parent_id, :in => Category.all.map(&:id), :unless => Proc.new { |c| c.parent_id.blank? } end my factories: Factory.define :category do |c| c.name "Category One" end Factory.define :category_2, :class => Category do |c| c.name "Category Two" end my model spec looks like this: require 'spec_helper' describe Category do before(:each) do @valid_attributes = { :name => "Category" } end it "should create a new instance given valid attributes" do Category.create!(@valid_attributes) end it "should have a name and it shouldn't be empty" do c = Category.new :name => nil c.should be_invalid c.name = "" c.should be_invalid end it "should not create a duplicate names" do Category.create!(@valid_attributes) Category.new(@valid_attributes).should be_invalid end it "should not save with invalid parent" do parent = Factory(:category) child = Category.new @valid_attributes child.parent_id = parent.id + 100 child.should be_invalid end it "should save with valid parent" do child = Factory.build(:category_2) child.parent = Factory(:category) # FIXME: make it pass, it works on cosole, but I don't know why the test is failing child.should be_valid end end I get the following error: 'Category should save with valid parent' FAILED Expected #<Category id: nil, name: "Category Two", parent_id: 5, created_at: nil, updated_at: nil to be valid, but it was not Errors: Parent is missing On console everything seems to be fine and work as expected: c1 = Category.new :name => "Parent Category" c1.valid? #=> true c1.save #=> true c1.id #=> 1 c2 = Category.new :name => "Child Category" c2.valid? #=> true c2.parent_id = 100 c2.valid? #=> false c2.parent_id = 1 c2.valid? #=> true I'm running rails 2.3.5, rspec 1.3.0 and rspec-rails 1.3.2 Anybody, any idea?

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  • Formatting the output of a custom tool so I can double click an error in Visual Studio and the file opens

    - by Ben Scott
    I've written a command line tool that preprocesses a number of files then compiles them using CodeDom. The tool writes a copyright notice and some progress text to the standard output, then writes any errors from the compilation step using the following format: foreach (var err in results.Errors) { // err is CompilerError var filename = "Path\To\input_file.xprt"; Console.WriteLine(string.Format( "{0} ({1},{2}): {3}{4} ({5})", filename, err.Line, err.Column, err.IsWarning ? "" : "ERROR: ", err.ErrorText, err.ErrorNumber)); } It then writes the number of errors, like "14 errors". This is an example of how the error appears in the console: Path\To\input_file.xrpt (73,28): ERROR: An object reference is required for the non-static field, method, or property 'Some.Object.get' (CS0120) When I run this as a custom tool in VS2008 (by calling it in the post-build event command line of one of my project's assemblies), the errors appear nicely formatted in the Error List, with the correct text in each column. When I roll over the filename the fully qualified path pops up. The line and column are different to the source file because of the preprocessing which is fine. The only thing that stands out is that the Project given in the list is the one that has the post-build event. The problem is that when I double click an error, nothing happens. I would have expected the file to open in the editor. I'm vaugely aware of the Microsoft.VisualStudio.Shell.Interop namespace but I think it should be possible just by writing to the standard output.

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  • Get highlighted state for NSButtonCell

    - by dvg
    I have a NSTableView that contains a NSButtonCell in one of the columns. To draw a custom background in neighbor cells (based on NSTextFieldCell) I use isHighlighted method: - (void)drawWithFrame:(NSRect)cellFrame inView:(NSView *)controlView { if ([self isHighlighted]) { //here I draw the cell background But for NSButtonCell isHighlighted shows only the button pressed state. How to determine when the NSButtonCell is selected, i.e. when it's highlighted in the row?

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  • How to open webpage in HIDDEN default browser? DELPHI

    - by obma
    I have been trying to open a hidden default browser from delphi but coulnd't. I tried ShellExecute(self.WindowHandle,'open','www.google.com',nil,nil, SW_HIDE); and I get my chrome browser open but not hidden, and it opens a tab not a new window, also tried with TStartupInfo with the same results. Is there another way to achieve this?

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  • problem with presentModalViewController

    - by pbcoder
    If my iPad is in Landscape mode and presentModalViewController is called the view automatically turns into portrait mode. Any solutions? UIViewController * start = [[UIViewController alloc]initWithNibName:@"SecondView" bundle:nil]; start.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal; start.modalPresentationStyle = UIModalPresentationFormSheet; [self presentModalViewController:start animated:YES]; In SecondView I've already added: - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { return YES; }

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  • Creating an Expando object in Ruby

    - by tyndall
    Is there a better way to write this Expando class? The way it is written does not work. I'm using Ruby 1.8.7 starting code quoted from https://gist.github.com/300462/3fdf51800768f2c7089a53726384350c890bc7c3 class Expando def method_missing(method_id, *arguments) if match = method_id.id2name.match(/(\w*)(\s*)(=)(\s*)(\.*)/) puts match[1].to_sym # think this was supposed to be commented self.class.class_eval{ attr_accessor match[1].to_sym } instance_variable_set("#{match[1]}", match[5]) else super.method_missing(method_id, *arguments) end end end person = Expando.new person.name = "Michael" person.surname = "Erasmus" person.age = 29

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  • Rails: include index with fields_for form helper

    - by Patrick Oscity
    i'm trying to build two models from one form by using the fields_for method. my code looks like this: <% for scale in @event.scales %> <% f.fields_for "scale[]", scale do |scale_form| %> <p> Scale<br /> <%= scale_form.label :name %> <%= scale_form.text_field :name %> <%= scale_form.label :price %> <%= scale_form.text_field :price %> </p> <% end %> <% end %> but unfortunately the output html is missing the id's of the scales: <p> Scale<br /> <label for="event_scale__name">Name</label> <input id="event_scale__name" name="event[scale][][name]" size="30" type="text" /> <label for="event_scale__price">Price</label> <input id="event_scale__price" name="event[scale][][price]" size="30" type="text" /> </p> ... here's the corresponding controller and model: class EventsController < ApplicationController ... def new @event = Event.new @providers = Provider.find(:all, :order => :name) 3.times { @event.scales.build } respond_to do |format| format.html end end ... end class Event < ActiveRecord::Base has_many :scales ... end what am i doing wrong?

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  • Re-define File::dirname ruby method

    - by jrhicks
    I'm trying to redefine the File.dirname method to first change %20s to spaces. But the following gives me an error class File old_dirname = instance_method(:dirname) define_method(:dirname) { |s| s = s.gsub("%20"," ") old_dirname.bind(self).call(s) } end This trhows a NameError exception: undefined method 'dirname' for class 'File' What is the right way to do this?

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  • Ruby Module Inclusion in Methods

    - by Federico Builes
    In class Foo I'd like to include method Bar under certain conditions: module Bar def some_method "orly" end end class Foo def initialize(some_condition) if !some_condition "bar" else class << self; include Bar; end end end end Is there any cleaner (and clearer) way to achieve the include in the method without having to do it inside the singleton class?

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  • simple question of pushViewController

    - by user217572
    messagecontroller is nothing but object of initialize nib file. [self.navigationController pushViewController:messageController animated:YES]; this statement executes in normal condition this statement also works on state maintainace testing , this line executes properly but not open new view ,why?

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