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• How can I maximally partition a set?

  - by Gregory Higley

  I'm trying to solve one of the Project Euler problems. As a consequence, I need an algorithm that will help me find all possible partitions of a set, in any order. For instance, given the set 2 3 3 5: 2 | 3 3 5 2 | 3 | 3 5 2 | 3 3 | 5 2 | 3 | 3 | 5 2 5 | 3 3 and so on. Pretty much every possible combination of the members of the set. I've searched the net of course, but haven't found much that's directly useful to me, since I speak programmer-ese not advanced-math-ese. Can anyone help me out with this? I can read pretty much any programming language, from BASIC to Haskell, so post in whatever language you wish.

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• Finding the angle of a fleeing dodo.

  - by donthackmyacc

  I'm coding some critter AI for a game i am working on for my Unity 3D project. I have no programming background and have been stumbling through this using tutorials and other peoples scripts. My problem is that i want my critter to run directly away from the player when the player kicks it. I need the dodo to run directly away from the player when kicked, and i dont know the math nor the syntax to calculate that angle. They are two characters moving independently through worldspace. Here is what i got so far: waypoint = (fleeWP.transform.position); transform.LookAt(Vector3(waypoint.x, transform.position.y, waypoint.z)); transform.Translate (Vector3.forward * speed * Time.deltaTime); This currently makes the critter move towards the waypoint, rather than away. I might be attacking this all wrong. Please chastise me.

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• What to beware of reading old Numarray tutorials and examples?

  - by DarenW

  Python currently uses Numpy for heavy duty math and image processing. The earlier Numeric and Numarray are obsolete, but still today there are many tutorials, notes, sample code and other documentation using them. Some of these cover special topics of interest, some are well written but haven't been updated or replaced, or are otherwise of use. Quite a bit is the same between Numeric, Numarray and Numpy, so I usually get good mileage out these older docs. Ocassionaly, though, I run into a line of code that results in error. Not often enough to remember how to get around it, but usually I figure it out at the cost of some time. What are the main things to watch out for when relying on such older documentation for current Numpy use? Is there a list of how to translate the differences that exist?

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• How to get dynamically session object in struts2

  - by Sujeet Singh

  I am trying to get dynamically session object in struts2 application. <s:if test="%{#session['resToken'].bookingType == 1}"> resToken can be get by <s:property value="%{resToken}">.. But I can't write <s:property> within <s:if test=""> its giving me error of double quotes.. org.apache.jasper.JasperException: /WEB-INF/jsp/booking/banquet/guest-Info-View.jsp(150,40) Unterminated &lt;s:if tag

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• Beginner Java Question about Integer.parseInt() and casting

  - by happysoul

  so when casting like in the statement below :- int randomNumber=(int) (Math.random()*5) it causes the random no. generated to get converted into an int.. Also there's this method I just came across Integer.parseInt() which does the same ! i.e return an integer Why two different ways to make a value an int ? Also I made a search and it says parseInt() takes string as an argument.. So does this mean that parseInt() is ONLY to convert String into integer ? What about this casting then (int) ?? Can we use this to convert a string to an int too ? sorry if it sounds like a dumb question..I am just confused and trying to understand Help ?

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• How can I rotate an image using Java/Swing and then set its origin to 0,0?

  - by JT

  I'm able to rotate an image that has been added to a JLabel. The only problem is that if the height and width are not equal, the rotated image will no longer appear at the JLabel's origin (0,0). Here's what I'm doing. I've also tried using AffineTransform and rotating the image itself, but with the same results. Graphics2D g2d = (Graphics2D)g; g2d.rotate(Math.toRadians(90), image.getWidth()/2, image.getHeight()/2); super.paintComponent(g2d); If I have an image whose width is greater than its height, rotating that image using this method and then painting it will result in the image being painted vertically above the point 0,0, and horizontally to the right of the point 0,0.

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• Algorithm to emulate mouse movement as a human does?

  - by Eye of Hell

  Hello I need to test a software that treats some mouse movements as "gestures". For such a task I need to emulate mouse movement from point A to point B, not in straight line, but as a real mouse moves - with curves, a bit of jaggedyness etc. Is there any available solution (algorithm/code itself, not a library/exe) that I can use? Of course I can write some simple sinusoidal math by myself, but this would be a very crude emulation of a human hand leading a mouse. Perhaps such a task has been solved already numerous times, and I can just borrow an existing code? :)

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• using pthread in c++

  - by ogzylz

  I am using pthread.h in a *.cc file. when I try to use pthread_exit(0); or pthread_join(mythrds[yy],NULL); it says : .cc:(.text+0x3e): undefined reference to `pthread_exit' when complied very similar code in a *.c file with gcc it work perfect. How Can I use pthread's in c++.. (I also added -lpthread) .. void *myThreads ( void *ptr ) { ... pthread_exit(0); } .. flags: g++ -lpthread -Wall -static -W -O9 -funroll-all-loops -finline -ffast-math

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• Use my own authentication in tomcat

  - by mabuzer

  how can I force tomcat to use my own implementation of Authenticator, and not the existing one like [FORM, BASIC, DIGEST,, etc]. I know if I added my authentication class name in org.apache.catalina.startup.Authenticators.properties it would work,,, any help please... I need an alternative for this...

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• Values of Variables Matrix NumPy

  - by Max Mines

  I'm working on a program that determines if lines intersect. I'm using matrices to do this. I understand all the math concepts, but I'm new to Python and NumPy. I want to add my slope variables and yint variables to a new matrix. They are all floats. I can't seem to figure out the correct format for entering them. Here's an example: import numpy as np x = 2 y = 5 w = 9 z = 12 I understand that if I were to just be entering the raw numbers, it would look something like this: matr = np.matrix('2 5; 9 12') My goal, though, is to enter the variable names instead of the ints.

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• ClassNotFoundException in Tomcat console when using jawr

  - by Jaya

  Hi, I am using Tomcat from Eclipse. When i try to start the server I am getting the following error in the console: java.lang.ClassNotFoundException: net.jawr.web.servlet.JawrServlet at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1516) When i deploy the war file in the Tomcat server outside of eclipse it is not having any problems. I am only getting this problem when i am trying to start tomcat from eclipse with jawr. Please let me know the solution for this problem. Thanks in advance, Jaya

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• Run java with highest security setting

  - by Ankiov Spetsnaz

  I'm currently writing an in house coding challenge web application and I am wondering if there is any other security precaution I would need to have other than below java option at runtime. java -Djava.security.manager=default Basically, challenges would be more of single threaded math and algorithm focused. So I would need to enable basic data structure objects and disable any file, sockets, threading or any thing that might be not so important. Based on my quick search turning on security manager as above seems to be a solution but since this is a security related I would like to be sure before it goes alive. Is there anything else I could do more?

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• Does this variable need to be declared volatile?

  - by titaniumdecoy

  Does the out variable in the MyThread class need to be declared volatile in this code or will the "volatility" of the stdout variable in the ThreadTest class carry over? import java.io.PrintStream; class MyThread implements Runnable { int id; PrintStream out; // should this be declared volatile? MyThread(int id, PrintStream out) { this.id = id; this.out = out; } public void run() { try { Thread.currentThread().sleep((int)(1000 * Math.random())); out.println("Thread " + id); } catch (InterruptedException e) { e.printStackTrace(); } } } public class ThreadTest { static volatile PrintStream stdout = System.out; public static void main(String[] args) { for (int i = 0; i < 10; i++) { new Thread(new MyThread(i, stdout)).start(); } } }

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• Problem with PHP/Java bridge.

  - by Jack

  I am using Tomcat 6. I am running a php script using the JavaBridge. I get the following error when I run my code. Fatal error: Call to undefined function mysqli_connect() in C:\Program Files\apache-tomcat-6.0.26\webapps\JavaBridge\xxxx\xxxxx.php on line 534 Please help.

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• How to extend a large website to iPhone app?

  - by xoail

  I am trying to create an iphone app for a large website (as big as amazon.com) and it involves using cookies and what not to get authenticated via the apache intercepter and access the web services exposed by the main website. For that I am looking for strategies to go about developing it. I am new to iphone dev and mostly looking for some architectural guidance. Does anyone know how does apps like ebay and amazon work seamlessly across the website and iphone?

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• execute javascript before return in php

  - by user354051

  I do have a custom php script that validates captcha code and sends an email. If php script is sending a mail successfully then it returns "true". This is done by: if(!$Error){ echo "true"; exit; } Before returning true, I would like to execute a jQuery command that should refresh the captcha image. I shouldn't be doing this is client side as it might be risky from spammers point of view. To refresh the captcha image, The command is: jQuery('#captcha').attr('src', ('php/captcha/captchaimage_show.php?' + Math.random())); I need to call this command from within php scripts before return any results by "echo" Prashant

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• Bit Flipping in Hex

  - by freyrs

  I have an 8 digit hexadecimal number of which I need certain digits to be either 0 or f. Given the specific place of the digits is there a quick way to generate the hex number with those places "flipped" to f. For example: flip_digits(1) = 0x000000f flip_digits(1,2,4) = 0x0000f0ff flip_digits(1,7,8) = 0xff00000f I'm doing this on an embedded device so I can't call any math libraries, I suspect it can be done with just bit shifts but I can't quite figure out the method. Any sort of solution (Python, C, Pseudocode) will work. Thanks in advance.

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• what is easiest way to setup a localhost in your computer?

  - by nabinb

  I am trying to learn website development so I wanted to setup a localhost on my pc. But I found setting up PHP, Apache, Mysql is quite tough than I thought? What is the easy way for this?

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• Direct video card access

  - by icemanind

  Guys, I am trying to write a class in C# that can be used as a direct replacement for the C# Bitmap class. What I want to do instead though is perform all graphic functions done on the bitmap using the power of the video card. From what I understand, functions such as DrawLine or DrawArc or DrawText are primitive functions that use simple cpu math algorithms to perform the job. I, instead, want to use the graphics card cpu and memory to do these and other advanced functions, such as skinning a bitmap (applying a texture) and true transparancy. My problem is, in C#, how do I access direct video functions? Is there a library or something I need?

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• Interesting AS3 hash situation. Is it really using strict equality as the documentation says?

  - by Triynko

  AS3 Code: import flash.utils.Dictionary; var num1:Number = Number.NaN; var num2:Number = Math.sqrt(-1); var dic:Dictionary = new Dictionary( true ); trace(num1); //NaN trace(num2); //NaN dic[num1] = "A"; trace( num1 == num2 ); //false trace( num1 === num2 ); //false trace( dic[num1] ); //A trace( dic[num2] ); //A Concerning the key comparison method... "The Dictionary class lets you create a dynamic collection of properties, which uses strict equality (===) for key comparison. When an object is used as a key, the object's identity is used to look up the object, and not the value returned from calling toString() on it." If Dictionary uses strict equality, as the documentation states, then how is it that num1 === num2 is false, and yet dic[num1] resolves to the same hash slot as dic[num2]?

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• Why are there so many floats in the Android API?

  - by Brian

  The default floating point type in Java is the double. If you hard code a constant like 2.5 into your program, Java makes it a double automatically. When you do an operation on floats or ints that could potentially benefit from more precision, the type is 'promoted' to a double. But in the Android API, everything seems to be a float from sound volumes to rectangle coordinates. There's a structure called RectF used in most drawing; the F is for float. It's really a pain for programmers who are casting promoted doubles back to (float) pretty often. Don't we all agree that Java code is messy and verbose enough as it is? Usually math coprocessors and accelerators prefer double in Java because it corresponds to one of the internal types. Is there something about Android's Dalvik VM that prefers floats for some reason? Or are all the floats just a result of perversion in API design?

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• What web servers use `COOKIE` instead of `HTTP_COOKIE`?

  - by Smack my batch up

  In the source code of the Perl module CGI.pm, in the submodule CGI::Cookies.pm, there is the following line: $raw_cookie = $ENV{HTTP_COOKIE} || $ENV{COOKIE}; I'm interested in $ENV{COOKIE} here. Are there any web servers (obsolete or otherwise) which transmit cookie information using the COOKIE environment variable instead of the HTTP_COOKIE used by Apache? I've never seen COOKIE and other CGI libraries don't seem to support it.

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• checking whether 4 points in a plane define a square ??

  - by osabri

  how to check whether 4 points in the plane define a square? what's the function which given a point and a value of the area of a square as input parameters returns four squares(define a corresponding type) with sides parallel to the x axis and y axis this how i start: #include <stdio.h> #include<math.h> struct point{ float x; float y; } typedef struct point POINT; struct square{ struct point p1; struct point p2; struct point p3; struct point p4; } typedef struct square SQUARE; int main() { int point; printf("point coordinate"); printf("\n\n"); printf("enter data\n");

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• Height of a binary tree

  - by Programmer

  Consider the following code: public int heightOfBinaryTree(Node node) { if (node == null) { return 0; } else { return 1 + Math.max(heightOfBinaryTree(node.left), heightOfBinaryTree(node.right)); } } I want to know the logical reasoning behind this code. How did people come up with it? Does some have an inductive proof? Moreover, I thought of just doing a BFS with the root of the binary tree as the argument to get the height of the binary tree. Is the previous approach better than mine?Why?

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• What types of Linux skills does a typical PHP developer need?

  - by markle976

  I am trying to improve my programming skills by learning more about frameworks, methodologies, and related technologies. I have seen a lot of job postings with requirements that also include Linux and/or Apache. So, my question is, what sort of things should I study in terms of Linux from a development standpoint?

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