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  • Defining the hash of an object as the sum of hashes of its members

    - by Space_C0wb0y
    I have a class that represents undirected edges in a graph. Every edge has two members vertex1 and vertex2 representing the vertices it connects. The problem is, that an edge can be specified two directions. My idea was now to define the hash of an edge as the sum of the hashes of its vertices. This way, the direction plays no role anymore, the hash would be the same. Are there any pitfalls with that?

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  • how to make a simple collision detection of bitmaps in Android

    - by Dritan Berna
    I already have a code with collision but it has check for winners and ontouch method that I don't really need because my bitmaps are moving itself and I just want them to collide if they overlap. private boolean checkCollision(Grafika first, Grafika second) { boolean retValue = false; int width = first.getBitmap().getWidth(); int height = first.getBitmap().getHeight(); int x1start = first.getCoordinates().getX(); int x1end = x1start + width; int y1start = first.getCoordinates().getY(); int y1end = y1start + height; int x2start = second.getCoordinates().getX(); int x2end = x2start + width; int y2start = second.getCoordinates().getY(); int y2end = y2start + height; if ((x2start >= x1start && x2start <= x1end) || (x2end >= x1start && x2end <= x1end)) { if ((y2start >= y1start && y2start <= y1end) || (y2end >= y1start && y2end <= y1end)) { retValue = true; } } return retValue; }

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  • Boolean checks with a single quadtree, or multiple quadtrees?

    - by Djentleman
    I'm currently developing a 2D sidescrolling shooter game for PC (think metroidvania but with a lot more happening at once). Using XNA. I'm utilising quadtrees for my spatial partitioning system. All objects will be encompassed by standard bounding geometry (box or sphere) with possible pixel-perfect collision detection implemented after geometry collision (depends on how optimised I can get it). These are my collision scenarios, with < representing object overlap (multiplayer co-op is the reason for the player<player scenario): Collision scenarios (true = collision occurs): Player <> Player = false Enemy <> Enemy = false Player <> Enemy = true PlayerBullet <> Enemy = true PlayerBullet <> Player = false PlayerBullet <> EnemyBullet = true PlayerBullet <> PlayerBullet = false EnemyBullet <> Player = true EnemyBullet <> Enemy = false EnemyBullet <> EnemyBullet = false Player <> Environment = true Enemy <> Environment = true PlayerBullet <> Environment = true EnemyBullet <> Environment = true Going off this information and the fact that were will likely be several hundred objects rendering on-screen at any given time, my question is as follows: Which method is likely to be the most efficient/optimised and why: Using a single quadtree with boolean checks for collision between the different types of objects. Using three quadtrees at once (player, enemy, environment), only testing the player and enemy trees against each other while testing both the player and enemy trees against the environment tree.

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  • Filezilla Install Problem: Hash Sum Mismatch

    - by kyleskool
    I'm new to the Ubuntu scene, and I tried to install Filezilla today by going to terminal and typing "sudo apt-get install filezilla", and got this error: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/universe/w/wxwidgets2.8/libwxbase2.8-0_2.8.12.1-6ubuntu2_amd64.deb Hash Sum mismatch Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/universe/w/wxwidgets2.8/libwxgtk2.8-0_2.8.12.1-6ubuntu2_amd64.deb Hash Sum mismatch Failed to fetch http://universe/t/tinyxml/libtinyxml2.6.2_2.6.2-1build1_amd64.deb Hash Sum mismatch Failed to fetch http://universe/f/filezilla/filezilla-common_3.5.3-1ubuntu2_all.deb Hash Sum mismatch Failed to fetch http://universe/f/filezilla/filezilla_3.5.3-1ubuntu2_amd64.deb Hash Sum mismatch E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing? Running it again with "--fix-missing" appended to the command didn't work, nor did running apt-get update. Any suggestion? Thanks!

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  • Good hash function for a 2d index

    - by rlbond
    I have a struct called Point. Point is pretty simple: struct Point { Row row; Column column; // some other code for addition and subtraction of points is there too } Row and Column are basically glorified ints, but I got sick of accidentally transposing the input arguments to functions and gave them each a wrapper class. Right now I use a set of points, but repeated lookups are really slowing things down. I want to switch to an unordered_set. So, I want to have an unordered_set of Points. Typically this set might contain, for example, every point on a 80x24 terminal = 1920 points. I need a good hash function. I just came up with the following: struct PointHash : public std::unary_function<Point, std::size_t> { result_type operator()(const argument_type& val) const { return val.row.value() * 1000 + val.col.value(); } }; However, I'm not sure that this is really a good hash function. I wanted something fast, since I need to do many lookups very quickly. Is there a better hash function I can use, or is this OK?

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  • Python minidom and UTF-8 encoded XML with hash references

    - by Jakob Simon-Gaarde
    Hi I am experiencing some difficulty in my home project where I need to parse a SOAP request. The SOAP is generated with gSOAP and involves string parameters with special characters like the danish letters "æøå". gSOAP builds SOAP requests with UTF-8 encoding by default, but instead of sending the special chatacters in raw format (ie. bytes C3A6 for the special character "æ") it sends what I think is called character hash references (ie. &#195;&#166;). I don't completely understand why gSOAP does it this way as I can see that it has marked the incomming payload as being UTF-8 encoded anyway (Content-Type: text/xml; charset=utf-8), but this is besides the question (I think). Anyway I guess gSOAP probably is obeying transport rules, or what? When I parse the request from gSOAP in python with xml.dom.minidom.parseString() I get element values as unicode objects which is fine, but the character hash references are not decoded as UTF-8 character codes. It unescapes the character hash references, but does not decode the string afterwards. In the end I have a unicode string object with UTF-8 encoding: So if the string "æble" is contained in the XML, it comes like this in the request: "&#195;&#166;ble" After parsing the XML the unicode string in the DOM Text Node's data member looks like this: u'\xc3\xa6ble' I would expect it to look like this: u'\xe6ble' What am I doing wrong? Should I unescape the SOAP XML before parsing it, or is it somewhere else I should be looking for the solution, maybe gSOAP? Thanks in advance. Best regards Jakob Simon-Gaarde

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  • How to create Hash object/array using jquery?

    - by Patrick
    Hi folks I know there is a Hash() object in the Javascript prototype framework, but is there anything in Jquery like this? As I would like to stick with one javascript framework, rather than mixing the Prototype Frame work and the JQuery framework and use at the same time, as I worry there will be conflict and create side-effects. So my question is: how to create Hash object/array using jquery? Here is my function: /* prototype framework, I want to change this to jQuery! */ var starSaves = new Hash(); function myHover(id, pos) { var starStrip = $('star_strip_' + id); if (starSaves.keys().indexOf(id) == -1) { var starSave = new Array(); var imgs = starStrip.select("img") alert(imgs); for (var i = 0; i < imgs.length; i++) { starSave[starSave.length] = imgs[i].src; if (i < pos) imgs[i].src = "/images/star_1.gif"; else imgs[i].src = "/images/star_0.gif"; } starSaves.set(id, starSave); } }

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  • XNA - 3D AABB collision detection and response

    - by fastinvsqrt
    I've been fiddling around with 3D AABB collision in my voxel engine for the last couple of days, and every method I've come up with thus far has been almost correct, but each one never quite worked exactly the way I hoped it would. Currently what I do is get two bounding boxes for my entity, one modified by the X translation component and the other by the Z component, and check if each collides with any of the surrounding chunks (chunks have their own octrees that are populated only with blocks that support collision). If there is a collision, then I cast out rays into that chunk to get the shortest collision distance, and set the translation component to that distance if the component is greater than the distance. The problem is that sometimes collisions aren't even registered. Here's a video on YouTube that I created showing what I mean. I suspect the problem may be with the rays that I cast to get the collision distance not being where I think they are, but I'm not entirely sure what would be wrong with them if they are indeed the problem. Here is my code for collision detection and response in the X direction (the Z direction is basically the same): // create the XZ offset vector Vector3 offsXZ = new Vector3( ( _translation.X > 0.0f ) ? SizeX / 2.0f : ( _translation.X < 0.0f ) ? -SizeX / 2.0f : 0.0f, 0.0f, ( _translation.Z > 0.0f ) ? SizeZ / 2.0f : ( _translation.Z < 0.0f ) ? -SizeZ / 2.0f : 0.0f ); // X physics BoundingBox boxx = GetBounds( _translation.X, 0.0f, 0.0f ); if ( _translation.X > 0.0f ) { foreach ( Chunk chunk in surrounding ) { if ( chunk.Collides( boxx ) ) { float dist = GetShortestCollisionDistance( chunk, Vector3.Right, offsXZ ) - 0.0001f; if ( dist < _translation.X ) { _translation.X = dist; } } } } else if ( _translation.X < 0.0f ) { foreach ( Chunk chunk in surrounding ) { if ( chunk.Collides( boxx ) ) { float dist = GetShortestCollisionDistance( chunk, Vector3.Left, offsXZ ) - 0.0001f; if ( dist < -_translation.X ) { _translation.X = -dist; } } } } And here is my implementation for GetShortestCollisionDistance: private float GetShortestCollisionDistance( Chunk chunk, Vector3 rayDir, Vector3 offs ) { int startY = (int)( -SizeY / 2.0f ); int endY = (int)( SizeY / 2.0f ); int incY = (int)Cube.Size; float dist = Chunk.Size; for ( int y = startY; y <= endY; y += incY ) { // Position is the center of the entity's bounding box Ray ray = new Ray( new Vector3( Position.X + offs.X, Position.Y + offs.Y + y, Position.Z + offs.Z ), rayDir ); // Chunk.GetIntersections(Ray) returns Dictionary<Block, float?> foreach ( var pair in chunk.GetIntersections( ray ) ) { if ( pair.Value.HasValue && pair.Value.Value < dist ) { dist = pair.Value.Value; } } } return dist; } I realize some of this code can be consolidated to help with speed, but my main concern right now is to get this bit of physics programming to actually work.

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  • Convert your Hash keys to object properties in Ruby

    - by kerry
    Being a Ruby noob (and having a background in Groovy), I was a little surprised that you can not access hash objects using the dot notation.  I am writing an application that relies heavily on XML and JSON data.  This data will need to be displayed and I would rather use book.author.first_name over book[‘author’][‘first_name’].  A quick search on google yielded this post on the subject. So, taking the DRYOO (Don’t Repeat Yourself Or Others) concept.  I came up with this: 1: class ::Hash 2:  3: # add keys to hash 4: def to_obj 5: self.each do |k,v| 6: if v.kind_of? Hash 7: v.to_obj 8: end 9: k=k.gsub(/\.|\s|-|\/|\'/, '_').downcase.to_sym 10: self.instance_variable_set("@#{k}", v) ## create and initialize an instance variable for this key/value pair 11: self.class.send(:define_method, k, proc{self.instance_variable_get("@#{k}")}) ## create the getter that returns the instance variable 12: self.class.send(:define_method, "#{k}=", proc{|v| self.instance_variable_set("@#{k}", v)}) ## create the setter that sets the instance variable 13: end 14: return self 15: end 16: end This works pretty well.  It converts each of your keys to properties of the Hash.  However, it doesn’t sit very well with me because I probably will not use 90% of the properties most of the time.  Why should I go through the performance overhead of creating instance variables for all of the unused ones? Enter the ‘magic method’ #missing_method: 1: class ::Hash 2: def method_missing(name) 3: return self[name] if key? name 4: self.each { |k,v| return v if k.to_s.to_sym == name } 5: super.method_missing name 6: end 7: end This is a much cleaner method for my purposes.  Quite simply, it checks to see if there is a key with the given symbol, and if not, loop through the keys and attempt to find one. I am a Ruby noob, so if there is something I am overlooking, please let me know.

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  • ruby hash problem

    - by sameera207
    HI All I have the following hash {:charge_payable_response={:return="700", :ns2="http://ws.myws.com/"}} How can i get the value of the key :return (700) thanks in advance cheers sameera

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  • How do I delete a [sub]hash based off of the keys/values of another hash?

    - by Zack
    Lets assume I have two hashes. One of them contains a set of data that only needs to keep things that show up in the other hash. e.g. my %hash1 = ( test1 => { inner1 => { more => "alpha", evenmore => "beta" } }, test2 => { inner2 => { more => "charlie", somethingelse => "delta" } }, test3 => { inner9999 => { ohlookmore => "golf", somethingelse => "foxtrot" } } ); my %hash2 = ( major=> { test2 => "inner2", test3 => "inner3" } ); What I would like to do, is to delete the whole subhash in hash1 if it does not exist as a key/value in hash2{major}, preferably without modules. The information contained in "innerX" does not matter, it merely must be left alone (unless the subhash is to be deleted then it can go away). In the example above after this operation is preformed hash1 would look like: my %hash1 = ( test2 => { inner2 => { more => "charlie", somethingelse => "delta" } }, ); It deletes hash1{test1} and hash1{test3} because they don't match anything in hash2. Here's what I've currently tried, but it doesn't work. Nor is it probably the safest thing to do since I'm looping over the hash while trying to delete from it. However I'm deleting at the each which should be okay? This was my attempt at doing this, however perl complains about: Can't use string ("inner1") as a HASH ref while "strict refs" in use at while(my ($test, $inner) = each %hash1) { if(exists $hash2{major}{$test}{$inner}) { print "$test($inner) is in exists.\n"; } else { print "Looks like $test($inner) does not exist, REMOVING.\n"; #not to sure if $inner is needed to remove the whole entry delete ($hash1{$test}{$inner}); } }

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  • Perl, creating a hash of hashes.

    - by Mike
    Based on my current understanding of hashes in Perl, I would expect this code to print "hello world." It instead prints nothing. %a=(); %b=(); $b{str} = "hello"; $a{1}=%b; $b=(); $b{str} = "world"; $a{2}=%b; print "$a{1}{str} $a{2}{str}"; I assume that a hash is just like an array, so why can't I make a hash contain another?

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  • Ruby method Array#<< not updating the array in hash

    - by Mladen Jablanovic
    Inspired by http://stackoverflow.com/questions/2552363/how-can-i-marshal-a-hash-with-arrays I wonder what's the reason that Array#<< won't work properly in the following code: h = Hash.new{Array.new} #=> {} h[0] #=> [] h[0] << 'a' #=> ["a"] h[0] #=> [] # why?! h[0] += ['a'] #=> ["a"] h[0] #=> ["a"] # as expected Does it have to do with the fact that << changes the array in-place, while Array#+ creates a new instance?

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  • Perl, get all hash values

    - by Mike
    Let's say in Perl I have a list of hash references, and each is required to contain a certain field, let's say foo. I want to create a list that contains all the mappings of foo. If there is a hash that does not contain foo the process should fail. @hash_list = ( {foo=>1}, {foo=>2} ); my @list = (); foreach my $item (@hash_list) { push(@list,$item->{foo}); } #list should be (1,2); Is there a more concise way of doing this in Perl?

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  • Flattening hash into string in Ruby

    - by fahadsadah
    Is there a way to flatten a hash into a string, with optional delimiters between keys and values, and key/value pairs? For example, print {:a => :b, :c => :d}.flatten('=','&') should print a=b&c=d I wrote some code to do this, but I was wondering if there was a neater way: class Hash def flatten(keyvaldelimiter, entrydelimiter) string = "" self.each do |key, value| key = "#{entrydelimiter}#{key}" if string != "" #nasty hack string += "#{key}#{keyvaldelimiter}#{value}" end return string end end print {:a => :b, :c => :d}.flatten('=','&') #=> 'c=d&a=b' Thanks

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  • Ruby: merge two hash as one and with value connected

    - by scalalala
    Hi guys: 2 hash: h1 = { "s1" => "2009-7-27", "s2" => "2010-3-6", "s3" => "2009-7-27" } h2 = { "s1" => "12:29:15", "s2" => "10:00:17", "s3" => "12:25:52" } I want to merge the two hash as one like this: h = { "s1" => "2009-7-27 12:29:15", "s2" => "2010-3-6 10:00:17", "s3" => "2009-7-27 2:25:52" } what is the best way to do this? thanks!

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  • C# XNA 2D Multiple boxes collision detection and movement

    - by zini
    Hi, I've been making simple game where you shoot boxes that are coming towards you. All game objects are simple rectangles. Now I have problem with collision detection; how to check where the collision comes so I can change the coordinates right? I have this kind of situation: http://imgur.com/8yjfW Imagine that all of those blocks are moving towards you (green box). If those orange boxes collide with each other, they should "avoid" themselves and not go through each other. I have class Enemy which has properties x, y and such. Now I'm doing the collision like this: // os.Count is an amount of other enemies colliding with this enemy if (os.Count == 0) { // If enemy doesn't collide with other enemy lasty = y; lastx = x; slope = (x - player.x) / (y - player.y); x += slope * l; // l is "movement speed" of enemy (float) if (y > player.y) { y = lasty; } else if (y < player.y) { y += l; } } else { foreach(Enemy b in os) { if (b.y > this.y) { // If some colliding enemy is closer player than this enemy, that closer one will be moved towards the player b.lasty = b.y; if (!BiggestY(os)) { // BiggestY returns true if this enemy has the biggest Y b.y += b.l; } b.x = b.lastx; } } } But this is very, very bad way to do this. I know it, but I just can't figure out other way. And as a matter in fact, this method doesn't even work pretty good; if multiple enemies are colliding same enemy they go through each other. I explained this pretty badly, but I hope that you understand this. And to sum up, as I said: How to check where the collision comes so I can change the coordinates right?

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  • eclipse 3.4 (ganymede) package collision with type

    - by Monis Iqbal
    We have a package that ends with exception e.g. package a.b.c.exception; Our code base had no issues up till eclipse 3.3, however when we shifted to eclipse 3.4, it started giving errors related to this package: "The package a.b.c.exception collides with a type" When I refactor the package name to a.b.c.exceptions, there are no issues. Is this due to a bug in eclipse 3.4 or is there some setting to rectify this behavior?

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  • Collision detection, alternatives to "push out"

    - by LaZe
    I'm moving a character (ellipsoid) around in my physics engine. The movement must be constrained by the static geometry, but should slide on the edges, so it won't be stuck. My current approach is to move it a little and then push it back out of the geometry. It seems to work, but I think it's mostly because of luck. I fear there must be some corner cases where this method will go haywire. For example a sharp corner where two walls keeps pushing the character into each other. How would a "state of the art" game engine solve this?

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  • Collision of dot and line in 2D space

    - by Anderiel
    So i'm trying to make my first game on android. The thing is i have a small moving ball and i want it to bounce from a line that i drew. For that i need to find if the x,y of the ball are also coordinates of one dot from the line. I tried to implement these equations about lines x=a1 + t*u1 y=a2 + t*u2 = (x-a1)/u1=(y-a2)/u2 (t=t which has to be if the point is on the line) where x and y are the coordinates im testing, dot[a1,a2] is a dot that is on the line and u(u1,u2) is the vector of the line. heres the code: public boolean Collided() { float u1 =Math.abs(Math.round(begin_X)-Math.round(end_X)); float u2 =Math.abs(Math.round(begin_Y)-Math.round(end_Y)); float t_x =Math.round((elect_X - begin_X)/u1); float t_y =Math.round((elect_Y - begin_Y)/u2); if(t_x==t_y) { return true; } else { return false; } } points [begin_X,end_X] and [begin_Y,end_Y] are the two points from the line and [elect_X,elect_Y] are the coordinates of the ball theoreticaly it should work, but in the reality the ball most of the time just goes straigth through the line or bounces somewhere else where it shouldnt

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