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  • What is the smallest amount of bits you can write twin-prime calculation?

    - by HH
    A succinct example in Python, its source. Explanation about the syntactic sugar here. s=p=1;exec"if s%p*s%~-~p:print`p`+','+`p+2`\ns*=p*p;p+=2\n"*999 The smallest amount of bits is defined by the smallest amount of 4pcs of things you can see with hexdump, it is not that precise measure but well-enough until an ambiguity. $ echo 's=p=1;exec"if s%p*s%~-~p:print`p`+','+`p+2`\ns*=p*p;p+=2\n"*999' > .test $ hexdump .test | wc 5 36 200 $ hexdump .test 0000000 3d73 3d70 3b31 7865 6365 6922 2066 2573 0000010 2a70 2573 2d7e 707e 703a 6972 746e 7060 0000020 2b60 2b2c 7060 322b 5c60 736e 3d2a 2a70 0000030 3b70 2b70 323d 6e5c 2a22 3939 0a39 000003e so in this case it is 31 because the initial parts are removed.

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  • Calculating percent "x/y * 100" always results in 0?

    - by Patrick Beninga
    In my assignment i have to make a simple version of Craps, for some reason the percentage assignments always produce 0 even when both variables are non 0, here is the code. import java.util.Random; Header, note the variables public class Craps { private int die1, die2,myRoll ,myBet,point,myWins,myLosses; private double winPercent,lossPercent; private Random r = new Random(); Just rolls two dies and produces their some. public int roll(){ die1 = r.nextInt(6)+1; die2 = r.nextInt(6)+1; return(die1 + die2); } The Play method, this just loops through the game. public void play(){ myRoll = roll(); point = 0; if(myRoll == 2 ||myRoll == 3 || myRoll == 12){ System.out.println("You lose!"); myLosses++; }else if(myRoll == 7 || myRoll == 11){ System.out.println("You win!"); myWins++; }else{ point = myRoll; do { myRoll = roll(); }while(myRoll != 7 && myRoll != point); if(myRoll == point){ System.out.println("You win!"); myWins++; }else{ System.out.println("You lose!"); myLosses++; } } } This is where the bug is, this is the tester method. public void tester(int howMany){ int i = 0; while(i < howMany){ play(); i++; } bug is right here in these assignments statements winPercent = myWins/i * 100; lossPercent = myLosses/i* 100; System.out.println("program ran "+i+" times "+winPercent+"% wins "+ lossPercent+"% losses with "+myWins+" wins and "+myLosses+" losses"); } }

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  • How do I determine when two moving points become visible to each other?

    - by Devin Jeanpierre
    Suppose I have two points, Point1 and Point2. At any given time, these points may be at different positions-- they are not necessarily static. Point1 is located at some position at time t, and its position is defined by the continuous functions x1(t) and y1(t) giving the x and y coordinates at time t. These functions are not differentiable, they are constructed piecewise from line segments. Point2 is the same, with x2(t) and y2(t), each function having the same properties. The obstacles that might prevent visibility are simple (and immobile) polygons. How can I find the boundary points for visibility? i.e. there are two kinds of boundaries: where the points become visible, and become invisible. For a become-visible boundary i, there exists some ?0, such that for any real number a, a ? (i-?, i) , Point1 and Point2 are not visible (i.e. the line segment that connects (x1(a), y1(a)) to (x2(a), y2(x)) crosses some obstacles). For b ? (i, i+?) they are visible. And it is the other way around for becomes-invisible. But can I find such a precise boundary, and if so, how?

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  • Dynamic creation of a pointer function in c++

    - by Liberalkid
    I was working on my advanced calculus homework today and we're doing some iteration methods along the lines of newton's method to find solutions to things like x^2=2. It got me thinking that I could write a function that would take two function pointers, one to the function itself and one to the derivative and automate the process. This wouldn't be too challenging, then I started thinking could I have the user input a function and parse that input (yes I can do that). But can I then dynamically create a pointer to a one-variable function in c++. For instance if x^2+x, can I make a function double function(double x){ return x*x+x;} during run-time. Is this remotely feasible, or is it along the lines of self-modifying code?

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  • Why do so many mathematicians format code so poorly? [closed]

    - by marcog
    I have done a fair amount of programming together with mathematicians. Now I am even teaching some high school kids coming from a mathematics background how to program. Most of these people format their code so hideously it's hard to believe. I've even worked with and taught mathematicians who will fight the auto-indenter! Why is this so common amongst mathematicians? BTW, this is one reason I have started teaching Python. Yet still they find ways other than indentation to produce whacked coding styles!

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  • Getting Factors of a Number

    - by Dave
    Hi Problem: I'm trying to refactor this algorithm to make it faster. What would be the first refactoring here for speed? public int GetHowManyFactors(int numberToCheck) { // we know 1 is a factor and the numberToCheck int factorCount = 2; // start from 2 as we know 1 is a factor, and less than as numberToCheck is a factor for (int i = 2; i < numberToCheck; i++) { if (numberToCheck % i == 0) factorCount++; } return factorCount; }

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  • How would you calculate all possible permutations of 0 through N iteratively?

    - by Bob Aman
    I need to calculate permutations iteratively. The method signature looks like: int[][] permute(int n) For n = 3 for example, the return value would be: [[0,1,2], [0,2,1], [1,0,2], [1,2,0], [2,0,1], [2,1,0]] How would you go about doing this iteratively in the most efficient way possible? I can do this recursively, but I'm interested in seeing lots of alternate ways to doing it iteratively.

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  • Convert arbitrary length to a value between -1.0 a 1.0?

    - by TheDarkIn1978
    How can I convert a length into a value in the range -1.0 to 1.0? Example: my stage is 440px in length and accepts mouse events. I would like to click in the middle of the stage, and rather than an output of X = 220, I'd like it to be X = 0. Similarly, I'd like the real X = 0 to become X = -1.0 and the real X = 440 to become X = 1.0. I don't have access to the stage, so i can't simply center-register it, which would make this process a lot easier. Also, it's not possible to dynamically change the actual size of my stage, so I'm looking for a formula that will translate the mouse's real X coordinate of the stage to evenly fit within a range from -1 to 1.

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  • Is there a 128 or 256 bit double class in .net?

    - by AKRamkumar
    I have an application that I want to be able to use large numbers and very precise numbers. For this, I needed a precision interpretation and IntX only works for integers. Is there a class in .net framework or even third party(preferably free) that would do this? Is there another way to do this?

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  • Wpf. Chart optimization. More than million points

    - by Evgeny
    I have custom control - chart with size, for example, 300x300 pixels and more than one million points (maybe less) in it. And its clear that now he works very slowly. I am searching for algoritm which will show only few points with minimal visual difference. I have link to component which have functionallity exactly what i need (2 million points demo): http://www.mindscape.co.nz/demo/SilverlightElements/demopage.html#/ChartOverviewPage I will be grateful for any matherials, links or thoughts how to realize such functionallity.

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  • Is there a transformation matrix that can scale the x and/or y axis logarithmically?

    - by Dave M
    I'm using .net WPF geometry classes to graph waveforms. I've been using the matrix transformations to convert from the screen coordinate space to my coordinate space for the waveform. Everything works great and it's really simple to keep track of my window and scaling, etc. I can even use the inverse transform to calculate the mouse position in terms of the coordinate space. I use the built in Scaling and Translation classes and then a custom matrix to do the y-axis flipping (there's not a prefab matrix for flipping). I want to be able to graph these waveforms on a log scale as well (either x axis or y axis or both), but I'm not sure if this is even possible to do with a matrix transformation. Does anyone know if this is possible, and if it is, what is the matrix?

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  • c++ Sorting a vector based on values of other vector, or what's faster?

    - by pollux
    Hi, There are a couple of other posts about sorting a vector A based on values in another vector B. Most of the other answers tell to create a struct or a class to combine the values into one object and use std::sort. Though I'm curious about the performance of such solutions as I need to optimize code which implements bubble sort to sort these two vectors. I'm thinking to use a vector<pair<int,int>> and sort that. I'm working on a blob-tracking application (image analysis) where I try to match previously tracked blobs against newly detected blobs in video frames where I check each of the frames against a couple of previously tracked frames and of course the blobs I found in previous frames. I'm doing this at 60 times per second (speed of my webcam). Any advice on optimizing this is appreciated. The code I'm trying to optimize can be shown here: http://code.google.com/p/projectknave/source/browse/trunk/knaveAddons/ofxBlobTracker/ofCvBlobTracker.cpp?spec=svn313&r=313 Thanks

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  • Double # showing 0 on android

    - by Dave
    I'm embarrassed to ask this question, but after 45 minutes of not finding a solution I will resort to public humiliation. I have a number that is being divided by another number and I'm storing that number in a double variable. The numbers are randomly generated, but debugging the app shows that both numbers are in fact being generated. Lets just say the numbers are 476 & 733. I then take the numbers and divide them to get the percentage 476/733 = .64 I then print out the variable and it's always set to 0. I've tried using DecimalFormat and NumberFormat. No matter what I try though it always says the variable is 0. I know there is something simple that I'm missing, I just can't find it =/.

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  • Javascript returns Nan in IE, FF ok

    - by user350184
    im very new to javascript, and writing this script to add up a shopping cart and print out subtotals and totals. it works in FF but not in IE. this function is called by onclick of one of three select options with a value of 0-25. it is in a js file called in the head. what it does is get the selected values as variables, parseint them, adds and multiplies, and changes the innerHTML of the table to reflect the subtotals, and total. FF does it great, but IE gives Nan. ive tried rewriting it a number of different ways, and many translations still work in FF but not IE8. ive made sure the variables and form id's arent repeated. function gen_invoice() { var scount = parseInt(document.shopcart.studentcount.value, 10); var ycount = parseInt(document.shopcart.youthcount.value, 10); var fcount = parseInt(document.shopcart.facultycount.value, 10); //html output source is 3 selects like this, with diff ids and names: //<select name="studentcount" id="studentcount"> //<option onclick="gen_invoice()" value="0">0 </option></select> var cardcost = parseInt(document.shopcart.cardprice.value, 10); //cardcost comes from hidden input value: //<input type="hidden" id="cardprice" name="cardprice" value="25"> var totalsum = scount + ycount + fcount; var grandtotal = totalsum * cardcost; document.getElementById('s_price').innerHTML = scount * cardcost; document.getElementById('y_price').innerHTML = ycount * cardcost; document.getElementById('f_price').innerHTML = fcount * cardcost; document.getElementById('grand').innerHTML = grandtotal; //.... } ...after this there are 3 long loops for writing out some other forms, but they dont work in IE either because they depend on the selected values to be an integer. this part happens first and returns Nan, so im sure the problem is here somwhere. I have literally hit my head on the table over this. You can imagine how frustrating it is to be able to write the entire rest of the site beautifully, but then fail at adding 3 numbers together. help please!

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  • need help with some basic java.

    - by Racket
    Hi, I'm doing the first chapter exercises on my Java book and I have been stuck for a problem for a while now. I'll print the question, prompt/read a double value representing a monetary amount. Then determine the fewest number of each bill and coin needed to represent that amount, starting with the highest (assume that a ten dollar bill is the maximum size needed). For example, if the value entered is 47,63 (forty-seven dollars and sixty-three cents), and the program should print the equivalent amount as: 4 ten dollar bills 1 five dollar bills 2 one dollar bills 2 quarters 1 dimes 0 nickels 3 pennies" etc. I'm doing an example exactly as they said in order to get an idea, as you will see in the code. Nevertheless, I managed to print 4 dollars, and I can't figure out how to get "1 five dollar", only 7 dollars (see code). Please, don't do the whole code for me. I just need some advice in regards to what I said. Thank you. import java.util.Scanner; public class PP29 { public static void main (String[] args) { Scanner sc = new Scanner (System.in); int amount; double value; double test1; double quarter; System.out.println("Enter \"double\" value: "); value = sc.nextDouble(); amount = (int) value / 10; // 47,63 / 10 = 4. int amount2 = (int) value % 10; // 47 - 40 = 7 quarter = value * 100; // 47,63 * 100 = 4736 int sum = (int) quarter % 100; // 4763 / 100 => 4763-4700 = 63. System.out.println(amount); System.out.println(amount2); } }

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  • Minimizing distance to a weighted grid

    - by Andrew Tomazos - Fathomling
    Lets suppose you have a 1000x1000 grid of positive integer weights W. We want to find the cell that minimizes the average weighted distance.to each cell. The brute force way to do this would be to loop over each candidate cell and calculate the distance: int best_x, best_y, best_dist; for x0 = 1:1000, for y0 = 1:1000, int total_dist = 0; for x1 = 1:1000, for y1 = 1:1000, total_dist += W[x1,y1] * sqrt((x0-x1)^2 + (y0-y1)^2); if (total_dist < best_dist) best_x = x0; best_y = y0; best_dist = total_dist; This takes ~10^12 operations, which is too long. Is there a way to do this in or near ~10^8 or so operations?

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  • How do I know when to increase or decrease angle to get a specific angle?

    - by Thomas
    Hi. I am programming a game and I have come to a very hard spot. Basically I have a circle and I have 2 angles on this circle. Angle 1 (A) is a point I want angle 2 (B) to go to. During my game every frame I need to check weither or not to increase or decrease my angle value by a certain amount (speed) to eventually reach the first angle. My question is how do I do this? I tried doing this but I don't seem to be doing it right. bool increase = false; float B = [self radiansToDegrees:tankAngle]; float A = [self radiansToDegrees:tankDestinationAngle]; float newAngle = B; if(B < A) { float C = B - (360 - A); float D = A - B; if(C < D) increase = false; else increase = true; } else if(B A) { float C = B - A; float D = A - (360 - B); if(C < D) increase = false; else increase = true; } if(increase) { newAngle += 1.0; } else { newAngle -= 1.0; } if(newAngle 360.0) { newAngle = 0 + (newAngle - 360.0); } else if(newAngle < 0.0) { newAngle = 360 + newAngle; } if(newAngle == 0) newAngle = 360; newAngle = [self degreesToRadians:newAngle]; [self setTanksProperPositionRotation:newAngle]; The basic effect I am trying to achieve is when the user makes a new point, which would be angle 1, angle 2 would move towards angle 1 choosing the fastest direction. I think I have spent around 4 hours trying to figure this out.

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