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  • How is the 'is' keyword implemented in Python?

    - by Srikanth
    ... the is keyword that can be used for equality in strings. >>> s = 'str' >>> s is 'str' True >>> s is 'st' False I tried both __is__() and __eq__() but they didn't work. >>> class MyString: ... def __init__(self): ... self.s = 'string' ... def __is__(self, s): ... return self.s == s ... >>> >>> >>> m = MyString() >>> m is 'ss' False >>> m is 'string' # <--- Expected to work False >>> >>> class MyString: ... def __init__(self): ... self.s = 'string' ... def __eq__(self, s): ... return self.s == s ... >>> >>> m = MyString() >>> m is 'ss' False >>> m is 'string' # <--- Expected to work, but again failed False >>> Thanks for your help!

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  • Django tests failing on invalid keyword argument

    - by Darwin Tech
    I have a models.py like so: from django.db import models from django.contrib.auth.models import User from datetime import datetime class UserProfile(models.Model): user = models.OneToOneField(User) def __unicode__(self): return self.user.username class Project(models.Model): user = models.ForeignKey(UserProfile) created = models.DateTimeField(auto_now_add=True) updated = models.DateTimeField(auto_now=True) product = models.ForeignKey('tool.product') module = models.ForeignKey('tool.module') model = models.ForeignKey('tool.model') zipcode = models.IntegerField(max_length=5) def __unicode__(self): return unicode(self.id) And my tests.py: from django.test import TestCase, Client # --- import app models from django.contrib.auth.models import User from tool.models import Module, Model, Product from user_profile.models import Project, UserProfile # --- unit tests --- # class UserProjectTests(TestCase): fixtures = ['admin_user.json'] def setUp(self): self.product1 = Product.objects.create( name='bar', ) self.module1 = Module.objects.create( name='foo', enable=True ) self.model1 = Model.objects.create( module=self.module1, name='baz', enable=True ) self.user1 = User.objects.get(pk=1) ... def test_can_create_project(self): self.project1 = Model.objects.create( user=self.user1, product=self.product1, module=self.module1, model=self.model1, zipcode=90210 ) self.assertEquals(self.project1.zipcode, 90210) But I get a TypeError: 'product' is an invalid keyword argument for this function error. I'm not sure what is failing but I'm guessing something to do with the FK relationships... Any help would be much appreciated.

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  • Use of var keyword in C#

    - by kronoz
    After discussion with colleagues regarding the use of the 'var' keyword in C# 3 I wondered what people's opinions were on the appropriate uses of type inference via var? For example I rather lazily used var in questionable circumstances, e.g.:- foreach(var item in someList) { // ... } // Type of 'item' not clear. var something = someObject.SomeProperty; // Type of 'something' not clear. var something = someMethod(); // Type of 'something' not clear. More legitimate uses of var are as follows:- var l = new List<string>(); // Obvious what l will be. var s = new SomeClass(); // Obvious what s will be. Interestingly LINQ seems to be a bit of a grey area, e.g.:- var results = from r in dataContext.SomeTable select r; // Not *entirely clear* what results will be here. It's clear what results will be in that it will be a type which implements IEnumerable, however it isn't entirely obvious in the same way a var declaring a new object is. It's even worse when it comes to LINQ to objects, e.g.:- var results = from item in someList where item != 3 select item; This is no better than the equivilent foreach(var item in someList) { // ... } equivilent. There is a real concern about type safety here - for example if we were to place the results of that query into an overloaded method that accepted IEnumerable<int> and IEnumerable<double> the caller might inadvertently pass in the wrong type. Edit - var does maintain strong typing but the question is really whether it's dangerous for the type to not be immediately apparent on definition, something which is magnified when overloads mean compiler errors might not be issued when you unintentionally pass the wrong type to a method. Related Question: http://stackoverflow.com/questions/633474/c-do-you-use-var

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  • proper use of volatile keyword

    - by luke
    I think i have a pretty good idea about the volatile keyword in java, but i'm thinking about re-factoring some code and i thought it would be a good idea to use it. i have a class that is basically working as a DB Cache. it holds a bunch of objects that it has read from a database, serves requests for those objects, and then occasionally refreshes the database (based on a timeout). Heres the skeleton public class Cache { private HashMap mappings =....; private long last_update_time; private void loadMappingsFromDB() { //.... } private void checkLoad() { if(System.currentTimeMillis() - last_update_time > TIMEOUT) loadMappingsFromDB(); } public Data get(ID id) { checkLoad(); //.. look it up } } So the concern is that loadMappingsFromDB could be a high latency operation and thats not acceptable, So initially i thought that i could spin up a thread on cache startup and then just have it sleep and then update the cache in the background. But then i would need to synchronize my class (or the map). and then i would just be trading an occasional big pause for making every cache access slower. Then i thought why not use volatile i could define the map reference as volatile private volatile HashMap mappings =....; and then in get (or anywhere else that uses the mappings variable) i would just make a local copy of the reference: public Data get(ID id) { HashMap local = mappings; //.. look it up using local } and then the background thread would just load into a temp table and then swap the references in the class HashMap tmp; //load tmp from DB mappings = tmp;//swap variables forcing write barrier Does this approach make sense? and is it actually thread-safe?

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  • Javascript function objects, this keyword points to wrong object

    - by Rody van Sambeek
    I've got a problem concerning the javascript "this" keyword when used within a javascript functional object. I want to be able to create an object for handling a Modal popup (JQuery UI Dialog). The object is called CreateItemModal. Which i want to be able to instantiate and pass some config settings. One of the config settings. When the show method is called, the dialog will be shown, but the cancel button is not functioning because the this refers to the DOM object instead of the CreateItemModal object. How can I fix this, or is there a better approach to put seperate behaviour in seperate "classes" or "objects". I've tried several approaches, including passing the "this" object into the events, but this does not feel like a clean solution. See (simplified) code below: function CreateItemModal(config) { // initialize some variables including $wrapper }; CreateItemModal.prototype.show = function() { this.$wrapper.dialog({ buttons: { // this crashes because this is not the current object here Cancel: this.close } }); }; CreateItemModal.prototype.close = function() { this.config.$wrapper.dialog('close'); };

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  • Python key word arguments

    - by pythonic metaphor
    I have several layers of function calls, passing around a common dictionary of key word arguments: def func1(**qwargs): func2(**qwargs) func3(**qwargs) I would like to supply some default arguments in some of the subsequent function calls, something like this: def func1(**qwargs): func2(arg = qwargs.get("arg", default), **qwargs) func3(**qwargs) The problem with this approach is that if arg is inside qwargs, a TypeError is raised with "got multiple values for keyword argument". I don't want to set qwargs["arg"] to default, because then func3 gets this argument without warrant. I could make a copy.copy of the qwargs and set "arg" in the copy, but qwargs could have large data structures in it and I don't want to copy them (maybe copy.copy wouldn't, only copy.deepcopy?). What's the pythonic thing to do here?

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  • C#: Using as bool? instead of object something = ViewState["hi"]

    - by Programmin Tool
    So I'm going through old code (2.0) and I came across this: object isReviewingValue = ViewState["IsReviewing"]; if (isReviewingValue is bool) { return (bool)isReviewingValue; } My first thought was to us the "as" keyword to avoid the unneeded (bool)isReviewingValue; But "as" only works with non value types. No problem, I just went ahead and did this: bool? isReviewingValue= ViewState["IsReviewing"] as bool?; if (isReviewingValue.HasValue) { return isReviewingValue.Value; } Question is: Besides looking a bit more readable, is this in fact better?

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  • Need help with joins in sqlalchemy

    - by Steve
    I'm new to Python, as well as SQL Alchemy, but not the underlying development and database concepts. I know what I want to do and how I'd do it manually, but I'm trying to learn how an ORM works. I have two tables, Images and Keywords. The Images table contains an id column that is its primary key, as well as some other metadata. The Keywords table contains only an id column (foreign key to Images) and a keyword column. I'm trying to properly declare this relationship using the declarative syntax, which I think I've done correctly. Base = declarative_base() class Keyword(Base): __tablename__ = 'Keywords' __table_args__ = {'mysql_engine' : 'InnoDB'} id = Column(Integer, ForeignKey('Images.id', ondelete='CASCADE'), primary_key=True) keyword = Column(String(32), primary_key=True) class Image(Base): __tablename__ = 'Images' __table_args__ = {'mysql_engine' : 'InnoDB'} id = Column(Integer, primary_key=True, autoincrement=True) name = Column(String(256), nullable=False) keywords = relationship(Keyword, backref='image') This represents a many-to-many relationship. One image can have many keywords, and one keyword can relate back to many images. I want to do a keyword search of my images. I've tried the following with no luck. Conceptually this would've been nice, but I understand why it doesn't work. image = session.query(Image).filter(Image.keywords.contains('boy')) I keep getting errors about no foreign key relationship, which seems clearly defined to me. I saw something about making sure I get the right 'join', and I'm using 'from sqlalchemy.orm import join', but still no luck. image = session.query(Image).select_from(join(Image, Keyword)).\ filter(Keyword.keyword == 'boy') I added the specific join clause to the query to help it along, though as I understand it, I shouldn't have to do this. image = session.query(Image).select_from(join(Image, Keyword, Image.id==Keyword.id)).filter(Keyword.keyword == 'boy') So finally I switched tactics and tried querying the keywords and then using the backreference. However, when I try to use the '.images' iterating over the result, I get an error that the 'image' property doesn't exist, even though I did declare it as a backref. result = session.query(Keyword).filter(Keyword.keyword == 'boy').all() I want to be able to query a unique set of image matches on a set of keywords. I just can't guess my way to the syntax, and I've spent days reading the SQL Alchemy documentation trying to piece this out myself. I would very much appreciate anyone who can point out what I'm missing.

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  • how to maintain the spaces between the chatacters?

    - by murali
    hi i am using the following code String keyword=request.getParameter("keyword"); keyword = keyword.toLowerCase(); keyword.replaceAll(" "," "); //first double space and then single space keyword = keyword.trim(); System.out.println(keyword); i am given the input as t s but iam getting as [3/12/10 12:07:10:431 IST] 0000002c SystemOut O t s // here i am getting the two spaces how can decrease two single space thanks, murali

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  • how to maintain the spaces between the characters?

    - by murali
    hi i am using the following code String keyword=request.getParameter("keyword"); keyword = keyword.toLowerCase(); keyword.replaceAll(" "," "); //first double space and then single space keyword = keyword.trim(); System.out.println(keyword); i am given the input as t s but iam getting as [3/12/10 12:07:10:431 IST] 0000002c SystemOut O t s // here i am getting the two spaces how can decrease two single space thanks, murali

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  • Source Control Checkin Comments at Top Of Source Files

    - by James Wiseman
    I've noticed a discrepancy with some source files in our system whereby some contain source-control checkin comments, and some do not. These comments are added automatically to the top of the file when it is checked in: * $Log: //vm1/Projects/Morpheus/Sleep.bdy-arc $ -- -- Rev 1.14 Apr 14 2009 15:32:52 John Smith --Fixed bugs 2292 and 2230. This seems to have been quite prevelant in all the compainies with which I have worked, but I must confess that I struggle to see the point. Generally the comments aren't that good, are ofen left by people who have long since departed, and even when they are of a high standard it is difficult to tie them to physical code changes. It also strikes me, that you are physically changing the file that you are checking in. Now, this may not be such a problem with files that will be compiled, but could be a disaster with others, e.g. JavaScript files. So really, my query is what was the motivation in concept behind providing this functionality in the first instance? Does anyone actually find these comments useful? Also, I would be curious to know if this was feature that is commonly supported within Source Control systems. I am aware of it with PVCS, VSS and Subversion (Subversion Keyword Substitution), however I wonder if it is also available in some of the more popular DVCSs. Your help, as always is much appreciated.

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  • Reference-type conversion operators: asking for trouble?

    - by Ben
    When I compile the following code using g++ class A {}; void foo(A&) {} int main() { foo(A()); return 0; } I get the following error messages: > g++ test.cpp -o test test.cpp: In function ‘int main()’: test.cpp:10: error: invalid initialization of non-const reference of type ‘A&’ from a temporary of type ‘A’ test.cpp:6: error: in passing argument 1 of ‘void foo(A&)’ After some reflection, these errors make plenty of sense to me. A() is just a temporary value, not an assignable location on the stack, so it wouldn't seem to have an address. If it doesn't have an address, then I can't hold a reference to it. Okay, fine. But wait! If I add the following conversion operator to the class A class A { public: operator A&() { return *this; } }; then all is well! My question is whether this even remotely safe. What exactly does this point to when A() is constructed as a temporary value? I am given some confidence by the fact that void foo(const A&) {} can accept temporary values according to g++ and all other compilers I've used. The const keyword can always be cast away, so it would surprise me if there were any actual semantic differences between a const A& parameter and an A& parameter. So I guess that's another way of asking my question: why is a const reference to a temporary value considered safe by the compiler whereas a non-const reference is not?

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  • Does searching a keyword on Google make the crawlers look harder in the future?

    - by Foo Bar
    Do the search requests made by the users influence the Google crawlers "attraction" by this keyword? Let's say Google has some hits on a specific keyword in the search index. And now I search for exactly this keyword. Will the Google crawlers react to the search and keep looking more intense for pages that could match this keyword? A reason why this could be important: Privacy when searching yourself. Assume you just want to know how much Google (and thus other people) can find out about you. If now any (statistical) additional search for your name trigger the crawlers even one step harder to find even more about you, it would have the negative effect that you would actually be found easier in the future, even though you had the intention and hope to find out how few Google finds about you. It's a bit like the dillema in quantum mechanis: Does observing the system automatically change the system?

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  • Camera for 2.5D Game

    - by me--
    I'm hoping someone can explain this to me like I'm 5, because I've been struggling with this for hours and simply cannot understand what I'm doing wrong. I've written a Camera class for my 2.5D game. The intention is to support world and screen spaces like this: The camera is the black thing on the right. The +Z axis is upwards in that image, with -Z heading downwards. As you can see, both world space and screen space have (0, 0) at their top-left. I started writing some unit tests to prove that my camera was working as expected, and that's where things started getting...strange. My tests plot coordinates in world, view, and screen spaces. Eventually I will use image comparison to assert that they are correct, but for now my test just displays the result. The render logic uses Camera.ViewMatrix to transform world space to view space, and Camera.WorldPointToScreen to transform world space to screen space. Here is an example test: [Fact] public void foo() { var camera = new Camera(new Viewport(0, 0, 250, 100)); DrawingVisual worldRender; DrawingVisual viewRender; DrawingVisual screenRender; this.Render(camera, out worldRender, out viewRender, out screenRender, new Vector3(30, 0, 0), new Vector3(30, 40, 0)); this.ShowRenders(camera, worldRender, viewRender, screenRender); } And here's what pops up when I run this test: World space looks OK, although I suspect the z axis is going into the screen instead of towards the viewer. View space has me completely baffled. I was expecting the camera to be sitting above (0, 0) and looking towards the center of the scene. Instead, the z axis seems to be the wrong way around, and the camera is positioned in the opposite corner to what I expect! I suspect screen space will be another thing altogether, but can anyone explain what I'm doing wrong in my Camera class? UPDATE I made some progress in terms of getting things to look visually as I expect, but only through intuition: not an actual understanding of what I'm doing. Any enlightenment would be greatly appreciated. I realized that my view space was flipped both vertically and horizontally compared to what I expected, so I changed my view matrix to scale accordingly: this.viewMatrix = Matrix.CreateLookAt(this.location, this.target, this.up) * Matrix.CreateScale(this.zoom, this.zoom, 1) * Matrix.CreateScale(-1, -1, 1); I could combine the two CreateScale calls, but have left them separate for clarity. Again, I have no idea why this is necessary, but it fixed my view space: But now my screen space needs to be flipped vertically, so I modified my projection matrix accordingly: this.projectionMatrix = Matrix.CreatePerspectiveFieldOfView(0.7853982f, viewport.AspectRatio, 1, 2) * Matrix.CreateScale(1, -1, 1); And this results in what I was expecting from my first attempt: I have also just tried using Camera to render sprites via a SpriteBatch to make sure everything works there too, and it does. But the question remains: why do I need to do all this flipping of axes to get the space coordinates the way I expect? UPDATE 2 I've since improved my rendering logic in my test suite so that it supports geometries and so that lines get lighter the further away they are from the camera. I wanted to do this to avoid optical illusions and to further prove to myself that I'm looking at what I think I am. Here is an example: In this case, I have 3 geometries: a cube, a sphere, and a polyline on the top face of the cube. Notice how the darkening and lightening of the lines correctly identifies those portions of the geometries closer to the camera. If I remove the negative scaling I had to put in, I see: So you can see I'm still in the same boat - I still need those vertical and horizontal flips in my matrices to get things to appear correctly. In the interests of giving people a repro to play with, here is the complete code needed to generate the above. If you want to run via the test harness, just install the xunit package: Camera.cs: using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Graphics; using System.Diagnostics; public sealed class Camera { private readonly Viewport viewport; private readonly Matrix projectionMatrix; private Matrix? viewMatrix; private Vector3 location; private Vector3 target; private Vector3 up; private float zoom; public Camera(Viewport viewport) { this.viewport = viewport; // for an explanation of the negative scaling, see: http://gamedev.stackexchange.com/questions/63409/ this.projectionMatrix = Matrix.CreatePerspectiveFieldOfView(0.7853982f, viewport.AspectRatio, 1, 2) * Matrix.CreateScale(1, -1, 1); // defaults this.location = new Vector3(this.viewport.Width / 2, this.viewport.Height, 100); this.target = new Vector3(this.viewport.Width / 2, this.viewport.Height / 2, 0); this.up = new Vector3(0, 0, 1); this.zoom = 1; } public Viewport Viewport { get { return this.viewport; } } public Vector3 Location { get { return this.location; } set { this.location = value; this.viewMatrix = null; } } public Vector3 Target { get { return this.target; } set { this.target = value; this.viewMatrix = null; } } public Vector3 Up { get { return this.up; } set { this.up = value; this.viewMatrix = null; } } public float Zoom { get { return this.zoom; } set { this.zoom = value; this.viewMatrix = null; } } public Matrix ProjectionMatrix { get { return this.projectionMatrix; } } public Matrix ViewMatrix { get { if (this.viewMatrix == null) { // for an explanation of the negative scaling, see: http://gamedev.stackexchange.com/questions/63409/ this.viewMatrix = Matrix.CreateLookAt(this.location, this.target, this.up) * Matrix.CreateScale(this.zoom) * Matrix.CreateScale(-1, -1, 1); } return this.viewMatrix.Value; } } public Vector2 WorldPointToScreen(Vector3 point) { var result = viewport.Project(point, this.ProjectionMatrix, this.ViewMatrix, Matrix.Identity); return new Vector2(result.X, result.Y); } public void WorldPointsToScreen(Vector3[] points, Vector2[] destination) { Debug.Assert(points != null); Debug.Assert(destination != null); Debug.Assert(points.Length == destination.Length); for (var i = 0; i < points.Length; ++i) { destination[i] = this.WorldPointToScreen(points[i]); } } } CameraFixture.cs: using Microsoft.Xna.Framework.Graphics; using System; using System.Collections.Generic; using System.Linq; using System.Windows; using System.Windows.Controls; using System.Windows.Media; using Xunit; using XNA = Microsoft.Xna.Framework; public sealed class CameraFixture { [Fact] public void foo() { var camera = new Camera(new Viewport(0, 0, 250, 100)); DrawingVisual worldRender; DrawingVisual viewRender; DrawingVisual screenRender; this.Render( camera, out worldRender, out viewRender, out screenRender, new Sphere(30, 15) { WorldMatrix = XNA.Matrix.CreateTranslation(155, 50, 0) }, new Cube(30) { WorldMatrix = XNA.Matrix.CreateTranslation(75, 60, 15) }, new PolyLine(new XNA.Vector3(0, 0, 0), new XNA.Vector3(10, 10, 0), new XNA.Vector3(20, 0, 0), new XNA.Vector3(0, 0, 0)) { WorldMatrix = XNA.Matrix.CreateTranslation(65, 55, 30) }); this.ShowRenders(worldRender, viewRender, screenRender); } #region Supporting Fields private static readonly Pen xAxisPen = new Pen(Brushes.Red, 2); private static readonly Pen yAxisPen = new Pen(Brushes.Green, 2); private static readonly Pen zAxisPen = new Pen(Brushes.Blue, 2); private static readonly Pen viewportPen = new Pen(Brushes.Gray, 1); private static readonly Pen nonScreenSpacePen = new Pen(Brushes.Black, 0.5); private static readonly Color geometryBaseColor = Colors.Black; #endregion #region Supporting Methods private void Render(Camera camera, out DrawingVisual worldRender, out DrawingVisual viewRender, out DrawingVisual screenRender, params Geometry[] geometries) { var worldDrawingVisual = new DrawingVisual(); var viewDrawingVisual = new DrawingVisual(); var screenDrawingVisual = new DrawingVisual(); const int axisLength = 15; using (var worldDrawingContext = worldDrawingVisual.RenderOpen()) using (var viewDrawingContext = viewDrawingVisual.RenderOpen()) using (var screenDrawingContext = screenDrawingVisual.RenderOpen()) { // draw lines around the camera's viewport var viewportBounds = camera.Viewport.Bounds; var viewportLines = new Tuple<int, int, int, int>[] { Tuple.Create(viewportBounds.Left, viewportBounds.Bottom, viewportBounds.Left, viewportBounds.Top), Tuple.Create(viewportBounds.Left, viewportBounds.Top, viewportBounds.Right, viewportBounds.Top), Tuple.Create(viewportBounds.Right, viewportBounds.Top, viewportBounds.Right, viewportBounds.Bottom), Tuple.Create(viewportBounds.Right, viewportBounds.Bottom, viewportBounds.Left, viewportBounds.Bottom) }; foreach (var viewportLine in viewportLines) { var viewStart = XNA.Vector3.Transform(new XNA.Vector3(viewportLine.Item1, viewportLine.Item2, 0), camera.ViewMatrix); var viewEnd = XNA.Vector3.Transform(new XNA.Vector3(viewportLine.Item3, viewportLine.Item4, 0), camera.ViewMatrix); var screenStart = camera.WorldPointToScreen(new XNA.Vector3(viewportLine.Item1, viewportLine.Item2, 0)); var screenEnd = camera.WorldPointToScreen(new XNA.Vector3(viewportLine.Item3, viewportLine.Item4, 0)); worldDrawingContext.DrawLine(viewportPen, new Point(viewportLine.Item1, viewportLine.Item2), new Point(viewportLine.Item3, viewportLine.Item4)); viewDrawingContext.DrawLine(viewportPen, new Point(viewStart.X, viewStart.Y), new Point(viewEnd.X, viewEnd.Y)); screenDrawingContext.DrawLine(viewportPen, new Point(screenStart.X, screenStart.Y), new Point(screenEnd.X, screenEnd.Y)); } // draw axes var axisLines = new Tuple<int, int, int, int, int, int, Pen>[] { Tuple.Create(0, 0, 0, axisLength, 0, 0, xAxisPen), Tuple.Create(0, 0, 0, 0, axisLength, 0, yAxisPen), Tuple.Create(0, 0, 0, 0, 0, axisLength, zAxisPen) }; foreach (var axisLine in axisLines) { var viewStart = XNA.Vector3.Transform(new XNA.Vector3(axisLine.Item1, axisLine.Item2, axisLine.Item3), camera.ViewMatrix); var viewEnd = XNA.Vector3.Transform(new XNA.Vector3(axisLine.Item4, axisLine.Item5, axisLine.Item6), camera.ViewMatrix); var screenStart = camera.WorldPointToScreen(new XNA.Vector3(axisLine.Item1, axisLine.Item2, axisLine.Item3)); var screenEnd = camera.WorldPointToScreen(new XNA.Vector3(axisLine.Item4, axisLine.Item5, axisLine.Item6)); worldDrawingContext.DrawLine(axisLine.Item7, new Point(axisLine.Item1, axisLine.Item2), new Point(axisLine.Item4, axisLine.Item5)); viewDrawingContext.DrawLine(axisLine.Item7, new Point(viewStart.X, viewStart.Y), new Point(viewEnd.X, viewEnd.Y)); screenDrawingContext.DrawLine(axisLine.Item7, new Point(screenStart.X, screenStart.Y), new Point(screenEnd.X, screenEnd.Y)); } // for all points in all geometries to be rendered, find the closest and furthest away from the camera so we can lighten lines that are further away var distancesToAllGeometrySections = from geometry in geometries let geometryViewMatrix = geometry.WorldMatrix * camera.ViewMatrix from section in geometry.Sections from point in new XNA.Vector3[] { section.Item1, section.Item2 } let viewPoint = XNA.Vector3.Transform(point, geometryViewMatrix) select viewPoint.Length(); var furthestDistance = distancesToAllGeometrySections.Max(); var closestDistance = distancesToAllGeometrySections.Min(); var deltaDistance = Math.Max(0.000001f, furthestDistance - closestDistance); // draw each geometry for (var i = 0; i < geometries.Length; ++i) { var geometry = geometries[i]; // there's probably a more correct name for this, but basically this gets the geometry relative to the camera so we can check how far away each point is from the camera var geometryViewMatrix = geometry.WorldMatrix * camera.ViewMatrix; // we order roughly by those sections furthest from the camera to those closest, so that the closer ones "overwrite" the ones further away var orderedSections = from section in geometry.Sections let startPointRelativeToCamera = XNA.Vector3.Transform(section.Item1, geometryViewMatrix) let endPointRelativeToCamera = XNA.Vector3.Transform(section.Item2, geometryViewMatrix) let startPointDistance = startPointRelativeToCamera.Length() let endPointDistance = endPointRelativeToCamera.Length() orderby (startPointDistance + endPointDistance) descending select new { Section = section, DistanceToStart = startPointDistance, DistanceToEnd = endPointDistance }; foreach (var orderedSection in orderedSections) { var start = XNA.Vector3.Transform(orderedSection.Section.Item1, geometry.WorldMatrix); var end = XNA.Vector3.Transform(orderedSection.Section.Item2, geometry.WorldMatrix); var viewStart = XNA.Vector3.Transform(start, camera.ViewMatrix); var viewEnd = XNA.Vector3.Transform(end, camera.ViewMatrix); worldDrawingContext.DrawLine(nonScreenSpacePen, new Point(start.X, start.Y), new Point(end.X, end.Y)); viewDrawingContext.DrawLine(nonScreenSpacePen, new Point(viewStart.X, viewStart.Y), new Point(viewEnd.X, viewEnd.Y)); // screen rendering is more complicated purely because I wanted geometry to fade the further away it is from the camera // otherwise, it's very hard to tell whether the rendering is actually correct or not var startDistanceRatio = (orderedSection.DistanceToStart - closestDistance) / deltaDistance; var endDistanceRatio = (orderedSection.DistanceToEnd - closestDistance) / deltaDistance; // lerp towards white based on distance from camera, but only to a maximum of 90% var startColor = Lerp(geometryBaseColor, Colors.White, startDistanceRatio * 0.9f); var endColor = Lerp(geometryBaseColor, Colors.White, endDistanceRatio * 0.9f); var screenStart = camera.WorldPointToScreen(start); var screenEnd = camera.WorldPointToScreen(end); var brush = new LinearGradientBrush { StartPoint = new Point(screenStart.X, screenStart.Y), EndPoint = new Point(screenEnd.X, screenEnd.Y), MappingMode = BrushMappingMode.Absolute }; brush.GradientStops.Add(new GradientStop(startColor, 0)); brush.GradientStops.Add(new GradientStop(endColor, 1)); var pen = new Pen(brush, 1); brush.Freeze(); pen.Freeze(); screenDrawingContext.DrawLine(pen, new Point(screenStart.X, screenStart.Y), new Point(screenEnd.X, screenEnd.Y)); } } } worldRender = worldDrawingVisual; viewRender = viewDrawingVisual; screenRender = screenDrawingVisual; } private static float Lerp(float start, float end, float amount) { var difference = end - start; var adjusted = difference * amount; return start + adjusted; } private static Color Lerp(Color color, Color to, float amount) { var sr = color.R; var sg = color.G; var sb = color.B; var er = to.R; var eg = to.G; var eb = to.B; var r = (byte)Lerp(sr, er, amount); var g = (byte)Lerp(sg, eg, amount); var b = (byte)Lerp(sb, eb, amount); return Color.FromArgb(255, r, g, b); } private void ShowRenders(DrawingVisual worldRender, DrawingVisual viewRender, DrawingVisual screenRender) { var itemsControl = new ItemsControl(); itemsControl.Items.Add(new HeaderedContentControl { Header = "World", Content = new DrawingVisualHost(worldRender)}); itemsControl.Items.Add(new HeaderedContentControl { Header = "View", Content = new DrawingVisualHost(viewRender) }); itemsControl.Items.Add(new HeaderedContentControl { Header = "Screen", Content = new DrawingVisualHost(screenRender) }); var window = new Window { Title = "Renders", Content = itemsControl, ShowInTaskbar = true, SizeToContent = SizeToContent.WidthAndHeight }; window.ShowDialog(); } #endregion #region Supporting Types // stupidly simple 3D geometry class, consisting of a series of sections that will be connected by lines private abstract class Geometry { public abstract IEnumerable<Tuple<XNA.Vector3, XNA.Vector3>> Sections { get; } public XNA.Matrix WorldMatrix { get; set; } } private sealed class Line : Geometry { private readonly XNA.Vector3 magnitude; public Line(XNA.Vector3 magnitude) { this.magnitude = magnitude; } public override IEnumerable<Tuple<XNA.Vector3, XNA.Vector3>> Sections { get { yield return Tuple.Create(XNA.Vector3.Zero, this.magnitude); } } } private sealed class PolyLine : Geometry { private readonly XNA.Vector3[] points; public PolyLine(params XNA.Vector3[] points) { this.points = points; } public override IEnumerable<Tuple<XNA.Vector3, XNA.Vector3>> Sections { get { if (this.points.Length < 2) { yield break; } var end = this.points[0]; for (var i = 1; i < this.points.Length; ++i) { var start = end; end = this.points[i]; yield return Tuple.Create(start, end); } } } } private sealed class Cube : Geometry { private readonly float size; public Cube(float size) { this.size = size; } public override IEnumerable<Tuple<XNA.Vector3, XNA.Vector3>> Sections { get { var halfSize = this.size / 2; var frontBottomLeft = new XNA.Vector3(-halfSize, halfSize, -halfSize); var frontBottomRight = new XNA.Vector3(halfSize, halfSize, -halfSize); var frontTopLeft = new XNA.Vector3(-halfSize, halfSize, halfSize); var frontTopRight = new XNA.Vector3(halfSize, halfSize, halfSize); var backBottomLeft = new XNA.Vector3(-halfSize, -halfSize, -halfSize); var backBottomRight = new XNA.Vector3(halfSize, -halfSize, -halfSize); var backTopLeft = new XNA.Vector3(-halfSize, -halfSize, halfSize); var backTopRight = new XNA.Vector3(halfSize, -halfSize, halfSize); // front face yield return Tuple.Create(frontBottomLeft, frontBottomRight); yield return Tuple.Create(frontBottomLeft, frontTopLeft); yield return Tuple.Create(frontTopLeft, frontTopRight); yield return Tuple.Create(frontTopRight, frontBottomRight); // left face yield return Tuple.Create(frontTopLeft, backTopLeft); yield return Tuple.Create(backTopLeft, backBottomLeft); yield return Tuple.Create(backBottomLeft, frontBottomLeft); // right face yield return Tuple.Create(frontTopRight, backTopRight); yield return Tuple.Create(backTopRight, backBottomRight); yield return Tuple.Create(backBottomRight, frontBottomRight); // back face yield return Tuple.Create(backBottomLeft, backBottomRight); yield return Tuple.Create(backTopLeft, backTopRight); } } } private sealed class Sphere : Geometry { private readonly float radius; private readonly int subsections; public Sphere(float radius, int subsections) { this.radius = radius; this.subsections = subsections; } public override IEnumerable<Tuple<XNA.Vector3, XNA.Vector3>> Sections { get { var latitudeLines = this.subsections; var longitudeLines = this.subsections; // see http://stackoverflow.com/a/4082020/5380 var results = from latitudeLine in Enumerable.Range(0, latitudeLines) from longitudeLine in Enumerable.Range(0, longitudeLines) let latitudeRatio = latitudeLine / (float)latitudeLines let longitudeRatio = longitudeLine / (float)longitudeLines let nextLatitudeRatio = (latitudeLine + 1) / (float)latitudeLines let nextLongitudeRatio = (longitudeLine + 1) / (float)longitudeLines let z1 = Math.Cos(Math.PI * latitudeRatio) let z2 = Math.Cos(Math.PI * nextLatitudeRatio) let x1 = Math.Sin(Math.PI * latitudeRatio) * Math.Cos(Math.PI * 2 * longitudeRatio) let y1 = Math.Sin(Math.PI * latitudeRatio) * Math.Sin(Math.PI * 2 * longitudeRatio) let x2 = Math.Sin(Math.PI * nextLatitudeRatio) * Math.Cos(Math.PI * 2 * longitudeRatio) let y2 = Math.Sin(Math.PI * nextLatitudeRatio) * Math.Sin(Math.PI * 2 * longitudeRatio) let x3 = Math.Sin(Math.PI * latitudeRatio) * Math.Cos(Math.PI * 2 * nextLongitudeRatio) let y3 = Math.Sin(Math.PI * latitudeRatio) * Math.Sin(Math.PI * 2 * nextLongitudeRatio) let start = new XNA.Vector3((float)x1 * radius, (float)y1 * radius, (float)z1 * radius) let firstEnd = new XNA.Vector3((float)x2 * radius, (float)y2 * radius, (float)z2 * radius) let secondEnd = new XNA.Vector3((float)x3 * radius, (float)y3 * radius, (float)z1 * radius) select new { First = Tuple.Create(start, firstEnd), Second = Tuple.Create(start, secondEnd) }; foreach (var result in results) { yield return result.First; yield return result.Second; } } } } #endregion }

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  • java inheritance keyword super()

    - by gucciv12
    requirement: Given the class 'ReadOnly' with the following behavior: A (protected) integer instance variable named 'val'. A constructor that accepts an integer and assigns the value of the parameter to the instance variable 'val'. A method name 'getVal' that returns the value of 'val'. Write a subclass named 'ReadWrite' with the following additional behavior: Any necessary constructors. a method named 'setVal' that accepts an integer parameter and assigns it the the 'val' instance variable. a method 'isDirty' that returns true if the setVal method was used to override the value of the 'val' variable. Code class ReadWrite extends ReadOnly { super(int val); void setVal(int val){this.val = val;} boolean isDirty() {if (setVal()(return true)) else return false;}} More Hints: ?     You should be using: modified ?     You should be using: private ?     You should be using: public

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  • Javascript new keyword and memory management

    - by Whyamistilltyping
    Coming from C++ it is hard grained into my mind that everytime I call new I call delete. In javascript I find myself calling new occasionally in my code but (hoping) the garbage collection functionality in the browser will take care of the mess for me. I don't like this - is there a 'delete' method in javascript and is how I use it different from in C++? Thanks.

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  • .NET using block and return; keyword

    - by Emre
    When I say this using (Entities db = new Entities()) { return db.TableName.AsQueryable().ToList(); } Do I by-pass the functionality of using block since I return something, and the method exits before exiting the using block, so I think the using block will not serve to its purpose and dispose the resource. Is this correct?

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  • EnvDTE partial class keyword

    - by Paul
    I'm introspecting on the code in a project using EnvDTE, and I want to be able to determine if they're a partial class, but it doesn't seem to exist in the namespace. Does anyone know how to do this?

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  • Error with using "dynamic" keyword in Silverlight app

    - by joemoe
    I get the following error: "One or more types required to compile a dynamic expression cannot be found. Are you missing references to Microsoft.CSharp.dll and System.Core.dll" I do have System.Core.dll, do have I to find Microsoft.CSharp somewhere? It wasn't part of the project and it isn't in the references list.

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  • Use of IsAssignableFrom and "is" keyword in C#

    - by fearofawhackplanet
    While trying to learn Unity, I keep seeing the following code for overriding GetControllerInstance in MVC: if(!typeof(IController).IsAssignableFrom(controllerType)) { ... } this seems to me a pretty convoluted way of basically writing if(controllerType is IController) { ... } I appreciate there are subtle differences between is and IsAssignableFrom, ie IsAssignableFrom doesn't include cast conversions, but I'm struggling to understand the implication of this difference in practical scenarios. When is it imporantant to choose IsAssignableFrom over is? What difference would it make in the GetControllerExample? if (!typeof(IController).IsAssignableFrom(controllerType)) throw new ArgumentException(...); return _container.Resolve(controllerType) as IController;

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  • Dynamics of the using keyword

    - by AngryHacker
    Consider the following code: // module level declaration Socket _client; void ProcessSocket() { _client = GetSocketFromSomewhere(); using (_client) { DoStuff(); // receive and send data Close(); } } void Close() { _client.Close(); _client = null; } Given that that the code calls the Close() method, which closes the _client socket and sets it to null, while still inside the `using' block, what exactly happens behind the scenes? Does the socket really get closed? Are there side effects? P.S. This is using C# 3.0 on the .NET MicroFramework, but I suppose the c#, the language, should function identically. The reason i am asking is that occasionally, very rarely, I run out of sockets (which is a very precious resource on a .NET MF devices).

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