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  • Is possible to initialize an object in javascript in this way?

    - by Kucebe
    I'd like to initialize an object in javascript calling directly a method that belongs to it: var obj = (function(){ return{ init: function(){ console.log("initialized!"); }, uninit: function(x){ console.log("uninitialized!"); } }; }).init(); //later obj.uninit(); obj.init(); This specific example doesn't work, is there something similar?

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  • C# assign values of array to separate variables in one line

    - by Sarah Vessels
    Can I assign each value in an array to separate variables in one line in C#? Here's an example in Ruby code of what I want: irb(main):001:0> str1, str2 = ["hey", "now"] => ["hey", "now"] irb(main):002:0> str1 => "hey" irb(main):003:0> str2 => "now" I'm not sure if what I'm wanting is possible in C#. Edit: for those suggesting I just assign the strings "hey" and "now" to variables, that's not what I want. Imagine the following: irb(main):004:0> val1, val2 = get_two_values() => ["hey", "now"] irb(main):005:0> val1 => "hey" irb(main):006:0> val2 => "now" Now the fact that the method get_two_values returned strings "hey" and "now" is arbitrary. In fact it could return any two values, they don't even have to be strings.

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  • if (self = [super init]) vs. if ((self = [super init]))

    - by JOM
    Was just doing a code review and started to wonder: I thought if (self = [super init]) checks whether assigning return value of [super init] to variable self was successful or not (value of operation). Thus (self = nil) would actually be TRUE. I thought if ((self = [super init])) checks what is the value of self after assignment (value of variable). Thus ((self = nil)) would be FALSE. Which one is the correct way to use when initializing your own classes? Apple documentation uses the former one (for example here), which style I'm actually using now.

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  • Best way in Python to determine all possible intersections in a matrix?

    - by ssweens
    So if I have a matrix (list of lists) of unique words as my column headings, document ids as my row headings, and a 0 or 1 as the values if the word exists in that particular document. What I'd like to know is how to determine all the possible combinations of words and documents where more than one word is in common with more than one document. So something like: [[Docid_3, Docid_5], ['word1', 'word17', 'word23']], [[Docid_3, Docid_9, Docid_334], ['word2', 'word7', 'word23', 'word68', 'word982']], and so on for each possible combination. Would love a solution that provides the complete set of combinations and one that yields only the combinations that are not a subset of another, so from the example, not [[Docid_3, Docid_5], ['word1', 'word17']] since it's a complete subset of the first example. I feel like there is an elegant solution that just isn't coming to mind and the beer isn't helping. Thanks.

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  • How can I draw the control points of a Bézier Path in Java?

    - by Sanoj
    I have created a Path of Bézier curves and it works fine to draw the path. But I don't know How I can draw the Control Points together with the Path. Is that possible or do I have to keep track of them in another datastructure? I am creating the path with: Path2D.Double path = new Path2D.Double(); path.moveTo(0,0); path.curveTo(5, 6, 23, 12, 45, 54); path.curveTo(34, 23, 12, 34, 2, 3); And drawing it with: g2.draw(path);

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  • Scaling vectors from a center point?

    - by user146780
    I'm trying to figure out if I have points that make for example a square: * * * * and let's say I know the center of this square. I want a formula that will make it for eample twice its size but from the center * * * * * * * * Therefore the new shape is twice as large and from the center of the polygon. It has to work for any shape not just squares. I'm looking more for the theory behind it more than the implementation. Thanks

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  • How is a constructor executed?

    - by simion
    I am doing some reviison from the lecture slides and it says a constructor is executed in the following way; If the constructor starts with this, recursively execute the indicated constructor, then go to step 4. Invoke the explicitly or implicitly indicated superclass constructor (unless this class is java.lang.Object) Initialise the fields of the object in the order in which they were declared in this class Execute the rest of the body of this constructor. What i dont undertsand is that, a constructor can never "start" with this, because even if it forms no class heirarchy/relationship then super() is inserted by default. How would this fit in with the description above? Thanks

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  • Is it bad practice to initialize a variable to a dummy value?

    - by froadie
    This question is a result of the answers to this question that I just asked. It was claimed that this code is "ugly" because it initializes a variable to a value that will never be read: String tempName = null; try{ tempName = buildFileName(); } catch(Exception e){ ... System.exit(1); } FILE_NAME = tempName; Is this indeed bad practice? Should one avoid initializing variables to dummy values that will never actually be used? (EDIT - And what about initializing a String variable to "" before a loop that will concatenate values to the String...? Or is this in a separate category? e.g. String whatever = ""; for(String str : someCollection){ whatever += str; } )

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  • C# Strange Behavior

    - by Betamoo
    I have a custom struct : struct A { public int y; } a custom class with empty constuctor: class B { public A a; public B() { } } and here is the main: static void Main(string[] args) { B b = new B(); b.a.y = 5;//No runtime errors! Console.WriteLine(b.a.y); } When I run the above program, it does not give me any errors, although I did not initialize struct A in class B constructor..'a=new A();'

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  • Is new int[10]() valid c++?

    - by Naveen
    While trying to answer this question I found that the code int* p = new int[10](); compiles fine with VC9 compiler and initializes the integers to 0. So my questions are: First of all is this valid C++ or is it a microsoft extension? Is it guaranteed to initialize all the elements of the array? Also, is there any difference if I do new int; or new int();? Does the latter guarantee to initialize the variable?

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  • Restrict sprite movement to vertical and horizontal

    - by Daniel Granger
    I have been battling with this for some time and my noob brain can't quite work it out. I have a standard tile map and currently use the following code to move my enemy sprite around the map -(void) movePlayer:(ccTime)deltaTime { if (CGPointEqualToPoint(self.position, requestedPosition)) return; float step = kPlayerSpeed * deltaTime; float dist = ccpDistance(self.position, requestedPosition); CGPoint vectorBetweenAB = ccpSub(self.position, requestedPosition); if (dist <= step) { self.position = requestedPosition; [self popPosition]; } else { CGPoint normVectorBetweenAB = ccpNormalize(vectorBetweenAB); CGPoint movementVectorForThisFrame = ccpMult(normVectorBetweenAB, step); if (abs(vectorBetweenAB.x) > abs(vectorBetweenAB.y)) { if (vectorBetweenAB.x > 0) { [self runAnimation:walkLeft]; } else { [self runAnimation:walkRight]; } } else { if (vectorBetweenAB.y > 0) { [self runAnimation:walkDown]; } else { [self runAnimation:walkUp]; } } if (self.position.x > movementVectorForThisFrame.x) { movementVectorForThisFrame.x = -movementVectorForThisFrame.x; } if (self.position.y > movementVectorForThisFrame.y) { movementVectorForThisFrame.y = -movementVectorForThisFrame.y; } self.position = ccpAdd(self.position, movementVectorForThisFrame); } } movePlayer: is called by the classes updateWithDeltaTime: method. the ivar requestedPosition is set in the updateWithDeltaTime method as well, it basically gets the next point out of a queue to move to. These points can be anywhere on the map, so if they are in a diagonal direction from the enemy the enemy sprite will move directly to that point. But how do I change the above code to restrict the movement to vertical and horizontal movement only so that the enemies movement 'staircases' its way along a diagonal path, taking the manhattan distance (I think its called). As shown by my crude drawing below... S being the start point F being the finish and the numbers being each intermediate point along its path to create a staircase type diagonal movement. Finally I intend to be able to toggle this behaviour on and off, so that I can choose whether or not I want the enemy to move free around the map or be restricted to this horizontal / vertical movement only. | | | | | | | | | | | | | | | | | | | | | |F| | | | | | | | | |5|4| | | | | | | | | |3|2| | | | | | | | | |1|S| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

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  • Is Java class initialized by the thread which use it for the first time?

    - by oo_olo_oo
    Lets assume following classes definition: public class A { public final static String SOME_VALUE; static { SOME_VALUE = "some.value"; } } public class B { private final String value = A.SOME_VALUE; } Assuming that the class A hasn't been loaded yet, what does happen when object of the class B is instantiated by some thread T? The class A has to be loaded and instantiated first. But my question is: if it's done in context of the thread T, or rather in context of some other (special) "classloader" thread?

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  • Unexpected output on initializing array by using both `element-by-element` & `designated` technique

    - by haccks
    C99 provides a feature to initialize arrays by using both element-by-element & designated method together as: int a[] = {2,1,[3] = 5,[5] = 9,6,[8] = 4}; On running the code: #include <stdio.h> int main() { int a[] = {2,1,[3] = 5,[0] = 9,4,[6] = 25}; for(int i = 0; i < sizeof(a)/sizeof(a[0]); i++) printf("%d ",a[i]); return 0; } (Note that Element 0 is initialized to 2 and then again initialised by designator [0] to 9) I was expecting that element 0(which is 2) will be replaced by 9(as designator [0] = 9) and hence o/p will become 9 1 0 5 4 0 25 Unfortunately I was wrong as o/p came; 9 4 0 5 0 0 25 Any explanation for unexpected o/p?

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  • How to map a long integer number to a N-dimensional vector of smaller integers (and fast inverse)?

    - by psihodelia
    Given a N-dimensional vector of small integers is there any simple way to map it with one-to-one correspondence to a large integer number? Say, we have N=3 vector space. Can we represent a vector X=[(int32)x1,(int32)x2,(int32)x3] using an integer (int48)y? The obvious answer is "Yes, we can". But the question is: "What is the fastest way to do this and its inverse operation?"

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  • RTS style fog of war woes

    - by Fricken Hamster
    So I'm trying to make a rts style line of sight fog of war style engine for my grid based game. Currently I am getting a set of vertices by raycasting in 360 degree. Then I use that list of vertices to do a graphics style polygon scanline fill to get a list of all points within the polygon. The I compare the new list of seen tiles and compare that with the old one and increment or decrement the world vision array as needed. The polygon scanline function is giving me trouble. I'm mostly following this http://www.cs.uic.edu/~jbell/CourseNotes/ComputerGraphics/PolygonFilling.html So far this is my code without cleaning anything up var edgeMinX:Vector.<int> = new Vector.<int>; var edgeMinY:Vector.<int> = new Vector.<int>; var edgeMaxY:Vector.<int> = new Vector.<int>; var edgeInvSlope:Vector.<Number> = new Vector.<Number>; var ilen:int = outvert.length; var miny:int = -1; var maxy:int = -1; for (i = 0; i < ilen; i++) { var curpoint:Point = outvert[i]; if (i == ilen -1) { var nextpoint:Point = outvert[0]; } else { nextpoint = outvert[i + 1]; } if (nextpoint.y == curpoint.y) { continue; } if (curpoint.y < nextpoint.y) { var curslope:Number = ((nextpoint.y - curpoint.y) / (nextpoint.x - curpoint.x)); edgeMinY.push(curpoint.y); edgeMinX.push(curpoint.x); edgeMaxY.push(nextpoint.y); edgeInvSlope.push(1 / curslope); if (curpoint.y < miny || miny == -1) { miny = curpoint.y; } if (nextpoint.y > maxy) { maxy = nextpoint.y; } } else { curslope = ((curpoint.y - nextpoint.y) / (curpoint.x - nextpoint.x)); edgeMinY.push(nextpoint.y); edgeMinX.push(nextpoint.x); edgeMaxY.push(curpoint.y); edgeInvSlope.push(1 / curslope); if (nextpoint.y < miny || miny == -1) { miny = curpoint.y; } if (curpoint.y > maxy) { maxy = nextpoint.y; } } } var activeMaxY:Vector.<int> = new Vector.<int>; var activeCurX:Vector.<Number> = new Vector.<Number>; var activeInvSlope:Vector.<Number> = new Vector.<Number>; for (var scanline:int = miny; scanline < maxy + 1; scanline++) { ilen = edgeMinY.length; for (i = 0; i < ilen; i++) { if (edgeMinY[i] == scanline) { activeMaxY.push(edgeMaxY[i]); activeCurX.push(edgeMinX[i]); activeInvSlope.push(edgeInvSlope[i]); //trace("added(" + edgeMinX[i]); edgeMaxY.splice(i, 1); edgeMinX.splice(i, 1); edgeMinY.splice(i, 1); edgeInvSlope.splice(i, 1); i--; ilen--; } } ilen = activeCurX.length; for (i = 0; i < ilen - 1; i++) { for (var j:int = i; j < ilen - 1; j++) { if (activeCurX[j] > activeCurX[j + 1]) { var tempint:int = activeMaxY[j]; activeMaxY[j] = activeMaxY[j + 1]; activeMaxY[j + 1] = tempint; var tempnum:Number = activeCurX[j]; activeCurX[j] = activeCurX[j + 1]; activeCurX[j + 1] = tempnum; tempnum = activeInvSlope[j]; activeInvSlope[j] = activeInvSlope[j + 1]; activeInvSlope[j + 1] = tempnum; } } } var prevx:int = -1; var jlen:int = activeCurX.length; for (j = 0; j < jlen; j++) { if (prevx == -1) { prevx = activeCurX[j]; } else { for (var k:int = prevx; k < activeCurX[j]; k++) { graphics.lineStyle(2, 0x124132); graphics.drawCircle(k * 20 + 10, scanline * 20 + 10, 5); if (k == prevx || k > activeCurX[j] - 1) { graphics.lineStyle(3, 0x004132); graphics.drawCircle(k * 20 + 10, scanline * 20 + 10, 2); } prevx = -1; //tileLightList.push(k, scanline); } } } ilen = activeCurX.length; for (i = 0; i < ilen; i++) { if (activeMaxY[i] == scanline + 1) { activeCurX.splice(i, 1); activeMaxY.splice(i, 1); activeInvSlope.splice(i, 1); i--; ilen--; } else { activeCurX[i] += activeInvSlope[i]; } } } It works in some cases but some of the x intersections are skipped, primarily when there are more than 2 x intersections in one scanline I think. Is there a way to fix this, or a better way to do what I described? Thanks

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  • How to avoid reallocation using the STL (C++)

    - by Tue Christensen
    This question is derived of the topic: http://stackoverflow.com/questions/2280655/vector-reserve-c I am using a datastructur of the type vector<vector<vector<double> > >. It is not possible to know the size of each of these vector (except the outer one) before items (doubles) are added. I can get an approximate size (upper bound) on the number of items in each "dimension". A solution with the shared pointers might be the way to go, but I would like to try a solution where the vector<vector<vector<double> > > simply has .reserve()'ed enough space (or in some other way has allocated enough memory). Will A.reserve(500) (assumming 500 is the size or, alternatively an upper bound on the size) be enough to hold "2D" vectors of large size, say [1000][10000]? The reason for my question is mainly because I cannot see any way of reasonably estimating the size of the interior of A at the time of .reserve(500). An example of my question: vector A; A.reserve(500+1); vector temp2; vector temp1 (666,666); for(int i=0;i<500;i++) { A.push_back(temp2); for(int j=0; j< 10000;j++) { A.back().push_back(temp1); } } Will this ensure that no reallocation is done for A? If temp2.reserve(100000) and temp1.reserve(1000) where added at creation will this ensure no reallocation at all will occur at all? In the above please disregard the fact that memory could be wasted due to conservative .reserve() calls. Thank you all in advance!

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  • What is wrong with my Dot Product?

    - by Clay Ellis Murray
    I am trying to make a pong game but I wanted to use dot products to do the collisions with the paddles, however whenever I make a dot product objects it never changes much from .9 this is my code to make vectors vector = { make:function(object){ return [object.x + object.width/2,object.y + object.height/2] }, normalize:function(v){ var length = Math.sqrt(v[0] * v[0] + v[1] * v[1]) v[0] = v[0]/length v[1] = v[1]/length return v }, dot:function(v1,v2){ return v1[0] * v2[0] + v1[1] * v2[1] } } and this is where I am calculating the dot in my code vector1 = vector.normalize(vector.make(ball)) vector2 = vector.normalize(vector.make(object)) dot = vector.dot(vector1,vector2) Here is a JsFiddle of my code currently the paddles don't move. Any help would be greatly appreciated

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  • What is wrong with my Dot Product? [Javascript]

    - by Clay Ellis Murray
    I am trying to make a pong game but I wanted to use dot products to do the collisions with the paddles, however whenever I make a dot product objects it never changes much from .9 this is my code to make vectors vector = { make:function(object){ return [object.x + object.width/2,object.y + object.height/2] }, normalize:function(v){ var length = Math.sqrt(v[0] * v[0] + v[1] * v[1]) v[0] = v[0]/length v[1] = v[1]/length return v }, dot:function(v1,v2){ return v1[0] * v2[0] + v1[1] * v2[1] } } and this is where I am calculating the dot in my code vector1 = vector.normalize(vector.make(ball)) vector2 = vector.normalize(vector.make(object)) dot = vector.dot(vector1,vector2) Here is a JsFiddle of my code currently the paddles don't move. Any help would be greatly appreciated

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  • deleting element objects of a std vector using erase : a) memory handling and b) better way?

    - by memC
    hi, I have a vec_A that stores instances of class A as: vec_A.push_back(A()); I want to remove some elements in the vector at a later stage and have two questions: a) The element is deleted as: vec_A.erase(iterator) Is there any additional code I need to add to make sure that there is no memory leak? . b) Assume that condition if(num <5) is if num is among a specific numberList. Given this, is there a better way to delete the elements of a vector than what I am illustrating below? #include<vector> #include<stdio.h> #include<iostream> class A { public: int getNumber(); A(int val); ~A(){}; private: int num; }; A::A(int val){ num = val; }; int A::getNumber(){ return num; }; int main(){ int i =0; int num; std::vector<A> vec_A; std::vector<A>::iterator iter; for ( i = 0; i < 10; i++){ vec_A.push_back(A(i)); } iter = vec_A.begin(); while(iter != vec_A.end()){ std::cout << "\n --------------------------"; std::cout << "\n Size before erase =" << vec_A.size(); num = iter->getNumber() ; std::cout << "\n num = "<<num; if (num < 5){ vec_A.erase(iter); } else{ iter++; } std::cout << "\n size after erase =" << vec_A.size(); } std::cout << "\nPress RETURN to continue..."; std::cin.get(); return 0; }

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  • Trying to sort the coefficients of the polynomial (z-a)(z-b)(z-c)...(z-n) into a vector

    - by pajamas
    So I have a factored polynomial of the form (z-a)(z-b)(z-c)...(z-n) for n an even positive integer. Thus the coefficient of z^k for 0 <= k < n will be the sum of all distinct n-k element products taken from the set {a,b,...,n} multiplied by (-1)^k, I hope that makes sense, please ask if you need more clarification. I'm trying to put these coefficients into a row vector with the first column containing the constant coefficient (which would be abc...n) and the last column containing the coefficient for z^n (which would be 1). I imagine there is a way to brute force this with a ton of nested loops, but I'm hoping there is a more efficient way. This is being done in Matlab (which I'm not that familiar with) and I know Matlab has a ton of algorithms and functions, so maybe its got something I can use. Can anyone think of a way to do this? Example: (z-1)(z-2)(z-3) = z^3 - (1 + 2 + 3)z^2 + (1*2 + 1*3 + 2*3)z - 1*2*3 = z^3 - 6z^2 + 11z - 6. Note that this example is n=3 odd, but n=4 would have taken too long to do by hand. Edit: Let me know if you think this would be better posted at TCS or Math Stack Exchange.

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  • How can I marshall a vector<int> from a C++ dll to a C# application?

    - by mmr
    I have a C++ function that produces a list of rectangles that are interesting. I want to be able to get that list out of the C++ library and back into the C# application that is calling it. So far, I'm encoding the rectangles like so: struct ImagePatch{ int xmin, xmax, ymin, ymax; } and then encoding some vectors: void MyFunc(..., std::vector<int>& rectanglePoints){ std::vector<ImagePatch> patches; //this is filled with rectangles for(i = 0; i < patches.size(); i++){ rectanglePoints.push_back(patches[i].xmin); rectanglePoints.push_back(patches[i].xmax); rectanglePoints.push_back(patches[i].ymin); rectanglePoints.push_back(patches[i].ymax); } } The header for interacting with C# looks like (and works for a bunch of other functions): extern "C" { __declspec(dllexport) void __cdecl MyFunc(..., std::vector<int>& rectanglePoints); } Are there some keywords or other things I can do to get that set of rectangles out? I found this article for marshalling objects in C#, but it seems way too complicated and way too underexplained. Is a vector of integers the right way to do this, or is there some other trick or approach?

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