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• Is this mingw bug ?

  - by Debanjan

  Hi, I have been trying to execute this program on my migw ,through code::blocks, #include <string.h> #include <math.h> #include <stdio.h> #define N 100 int p[N / 64]; int pr[N]; int cnt; void sieve() { int i,j; for(i=0;i<N;i++) pr[i]=1; pr[0]=pr[1]=0; for(i=2;i<N;i++) if(pr[i]) { p[cnt]=i; cnt++; for(j=i+i;j<=N;j+=i) pr[j]=0; } } int main(){ sieve(); int i; for(i=0;i<cnt;i++) printf("%d ",p[i]); puts(""); printf("Total number of prime numbers : %d",cnt); return 0; } In My system the output is : 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 Total number of prime numbers : 22 Which is completely insane,since I am completely sure about the implementation of my algorithm. So I decided to try it in Ideone where it gives correct output.Can anybody point out the reason ?

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• byte + byte = int... why?

  - by Robert C. Cartaino

  Looking at this C# code... byte x = 1; byte y = 2; byte z = x + y; // ERROR: Cannot implicitly convert type 'int' to 'byte' The result of any math performed on byte (or short) types is implicitly cast back to an integer. The solution is to explicitly cast the result back to a byte, so... byte z = (byte)(x + y); // works What I am wondering is why? Is it architectural? Philosophical? We have: int + int = int long + long = long float + float = float double + double = double So why not: byte + byte = byte short + short = short ? A bit of background: I am performing a long list of calculations on "small numbers" (i.e. < 8) and storing the intermediate results in a large array. Using a byte array (instead of an int array) is faster (because of cache hits). But the extensive byte-casts spread through the code make it that much more unreadable.

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• jquery ajax result with a wrong format

  - by ???

  I am facing a problem which is the result processed by AJAX, this situation is I would like to pass the result (from AJAX) 'f f f f \'' into get_option(''), I don't know why it become like this:- <li \'');="" f="" onclick="get_option('f" class="option normal_size"> <a href="javascript:void(0);">f f f f \'</a> </li> What I want is :- <li onclick="get_option('f f f f\'')" class="option normal_size"> <a href="javascript:void(0);">f f f f \'</a> </li> I guess the problem might be the space, but I don't know how to solve it, can anyone do me a favour? my AJAX coding is:- .ajax({ url:'inc_board_saving.php?board_title_input='+board_title_input_encode+'&cate_selected='+cate_selected_input_encode+'&cate_setting_selected='+cate_setting_selected, type:'GET', data:"nums="+Math.random()*1235, success: function(data){ try{ var content=""; var obj = eval('('+data+')'); for (var i=0;i<obj.length;i++){ content += "<li class='option normal_size' onclick=get_option('"+obj[i].board_name_encode+"');><a href='javascript:void(0);'>"+obj[i].board_name+"</a></li>"; } }catch(e){ return; } } }); Result:- [{"board_id":"66","board_name":"f f f f '","board_name_encode":"f f f f \'"},{"board_id":"65","board_name":"t t t t t","board_name_encode":"t t t t t"},{"board_id":"64","board_name":"yy yyy yy","board_name_encode":"yy yyy yy"}] Thanks all

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• Time complexity of a powerset generating function

  - by Lirik

  I'm trying to figure out the time complexity of a function that I wrote (it generates a power set for a given string): public static HashSet<string> GeneratePowerSet(string input) { HashSet<string> powerSet = new HashSet<string>(); if (string.IsNullOrEmpty(input)) return powerSet; int powSetSize = (int)Math.Pow(2.0, (double)input.Length); // Start at 1 to skip the empty string case for (int i = 1; i < powSetSize; i++) { string str = Convert.ToString(i, 2); string pset = str; for (int k = str.Length; k < input.Length; k++) { pset = "0" + pset; } string set = string.Empty; for (int j = 0; j < pset.Length; j++) { if (pset[j] == '1') { set = string.Concat(set, input[j].ToString()); } } powerSet.Add(set); } return powerSet; } So my attempt is this: let the size of the input string be n in the outer for loop, must iterate 2^n times (because the set size is 2^n). in the inner for loop, we must iterate 2*n times (at worst). 1. So Big-O would be O((2^n)*n) (since we drop the constant 2)... is that correct? And n*(2^n) is worse than n^2. if n = 4 then (4*(2^4)) = 64 (4^2) = 16 if n = 100 then (10*(2^10)) = 10240 (10^2) = 100 2. Is there a faster way to generate a power set, or is this about optimal?

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• Detect mouseover and show tooltip text for dots on an HTML Canvas

  - by carl asquith

  Ive recently created a "map" although not very sophisticated (im working on it) it has the basic function and is generally heading in the right direction. If you look at it you can see a tiny red dots and on those tiny red dots i want to mouseover it and see text basically but ive had a bit of trouble getting the code right. http://hummingbird2.x10.mx/website%20creation/mainpage.htm This is all the code so far. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Oynx Warrior</title> <link rel="stylesheet" type="text/css" href="mystyle.css" /> </head> <body> <h1>Oynx Warrior</h1> <canvas id="myCanvas" width="500" height="500" style="border:1px solid #c3c3c3;"> Your browser does not support the canvas element. </canvas> <script type="text/javascript"> var c=document.getElementById("myCanvas"); var cxt=c.getContext("2d"); cxt.fillStyle="#red"; cxt.beginPath(); cxt.arc(50,50,1,0,Math.PI*2,true); cxt.closePath(); cxt.fill(); </script> </body> </html>

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• Refresh Div with Jquery at fixed time

  - by Ben C

  I've got a php script that tells me when the next bus is due, and at the moment I'm refreshing this into a div, using jquery, every minute or so. Now, because I know the time at which the data will change (after the bus has come), I want it to refresh the div at this time (or just after, doesn't really matter). I should point out that I'm fairly new to js, but this is what I've got so far: var nextbustime = $('#bus').contents(); var nextbustime = new Date(nextbustime); var now = new Date(); var t = nextbustime.getTime() - now.getTime(); var refreshId = setTimeout(function() { $('#bus').fadeOut("slow").load('modules/bus.php?randval='+ Math.random()).fadeIn("slow"); }, t); The div is loaded originally with a php include. Naturally, what I've done doesn't work at all. Do I need some loops going on? Do I need to refresh the time calculator? Please please help! Thanks in advance...

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• Deterministic floating point and .NET

  - by code2code

  How can I guarantee that floating point calculations in a .NET application (say in C#) always produce the same bit-exact result? Especially when using different versions of .NET and running on different platforms (x86 vs x86_64). Inaccuracies of floating point operations do not matter. In Java I'd use strictfp. In C/C++ and other low level languages this problem is essentially solved by accessing the FPU / SSE control registers but that's probably not possible in .NET. Even with control of the FPU control register the JIT of .NET will generate different code on different platforms. Something like HotSpot would be even worse in this case... Why do I need it? I'm thinking about writing a real-time strategy (RTS) game which heavily depends on fast floating point math together with a lock stepped simulation. Essentially I will only transmit user input across the network. This also applies to other games which implement replays by storing the user input. Not an option are: decimals (too slow) fixed point values (too slow and cumbersome when using sqrt, sin, cos, tan, atan...) update state across the network like an FPS: Sending position information for hundreds or a few thousand units is not an option Any ideas?

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• WPF Drag-to-scroll doesn't work correctly.

  - by Garegin

  Hi all, I am tying to realize a drag-to-scroll functionality in my application and have problems on my way. Can anybody help me? I have a ScrollViewer and inside it an ItemsControl and within ItemsTemplate I have a UserControl. I want to drag that UserControl within ItemsControl. I want the ScrollViewer to scroll down, when I am dragging to the boundaries of the ItemsControl. protected override void OnPreviewMouseMove(System.Windows.Input.MouseEventArgs e) { if (this.IsMouseCaptured) { // Get the new mouse position. Point mouseDragCurrentPoint = e.GetPosition(this); if (Math.Abs(mouseDragCurrentPoint.Y - this.ActualHeight) <= 50) { this._scrollStartOffset.Y += 5; _containingScrollViewer.ScrollToVerticalOffset(this._scrollStartOffset.Y); } if (mouseDragCurrentPoint.Y <= 50) { this._scrollStartOffset.Y -= 5; _containingScrollViewer.ScrollToVerticalOffset(this._scrollStartOffset.Y); } } base.OnPreviewMouseMove(e); } When i start dragging by calling DragDrop.DoDragDrop() scrolling don't happens. But when i disable dragging, the ScrollViewer scrolls down dependong on mouse position. Maybe there's something that i don't take into accont about dragging and Capturing the mouse? Thanks for attention. Garegin

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• Int - number too large. How to get program to fail?

  - by Dave

  Hi Problem: How do you get a program to fail if a number goes beyond the bounds of its type? This code below gives the wrong answer for sum of primes under 2 million as I'd used an int instead of a long. [TestMethod] public void CalculateTheSumOfPrimesBelow2million() { int result = PrimeTester.calculateTheSumOfPrimesBelow(2000000); // 2million Assert.AreEqual(1, result); // 1,179,908,154 .. this was what I got with an int... // correct answer was 142,913,828,922 with a long } public static class PrimeTester { public static int calculateTheSumOfPrimesBelow(int maxPrimeBelow) { // we know 2 is a prime number int sumOfPrimes = 2; int currentNumberBeingTested = 3; while (currentNumberBeingTested < maxPrimeBelow) { double squareRootOfNumberBeingTested = (double)Math.Sqrt(currentNumberBeingTested); bool isPrime = true; for (int i = 2; i <= squareRootOfNumberBeingTested; i++) { if (currentNumberBeingTested % i == 0) { isPrime = false; break; } } if (isPrime) sumOfPrimes += currentNumberBeingTested; currentNumberBeingTested += 2; // as we don't want to test even numbers } return sumOfPrimes; } }

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• ActionListener isn't Implementing

  - by Nick Gibson

  JFrameWithPanel is not abstract and does not override abstract method actionPerformed(java.awt.event.ActionEvent) in java.awt.event.ActionListener public class JFrameWithPanel extends JFrame implements ActionListener I Don't get this code. Book and Java site tells me this is the syntax for the method, but again this error shows up constantly. import javax.swing.*; import javax.swing.JOptionPane; import java.awt.*; import java.awt.event.*; import java.lang.Math.*; import java.lang.Integer.*; import java.util.*; import java.util.Random; import java.io.*; import java.text.*; import java.text.DecimalFormat.*; public class JFrameWithPanel extends JFrame implements ActionListener { JButton button = new JButton("Exit"); public JFrameWithPanel() { super("JFrame with Panel"); JComboBox packageChoice = new JComboBox(); packageChoice.addItem("A+ Certification"); packageChoice.addItem("Network+ Certification "); packageChoice.addItem("Security+ Certifictation"); packageChoice.addItem("CIT Full Test Package"); packageChoice.addActionListener(this); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); JPanel pane = new JPanel(); pane.add(button); pane.add(packageChoice); setContentPane(pane); setSize(200,100); setVisible(true); } } then later public class CreateJFrameWithPanel { public static void main(String[] args) { JFrameWithPanel panel = new JFrameWithPanel(); } }

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• Cannot make a static reference to the non-static type MyRunnable

  - by kaiwii ho

  Here is the whole code : import java.util.ArrayList; public class Test{ ThreadLocal<ArrayList<E>>arraylist=new ThreadLocal<ArrayList<E>>(){ @Override protected ArrayList<E> initialValue() { // TODO Auto-generated method stub //return super.initialValue(); ArrayList<E>arraylist=new ArrayList<E>(); for(int i=0;i<=20;i++) arraylist.add((E) new Integer(i)); return arraylist; } }; class MyRunnable implements Runnable{ private Test mytest; public MyRunnable(Test test){ mytest=test; // TODO Auto-generated constructor stub } @Override public void run() { System.out.println("before"+mytest.arraylist.toString()); ArrayList<E>myarraylist=(ArrayList<E>) mytest.arraylist.get(); myarraylist.add((E) new Double(Math.random())); mytest.arraylist.set(myarraylist); System.out.println("after"+mytest.arraylist.toString()); } // TODO Auto-generated method stub } public static void main(String[] args){ Test test=new Test<Double>(); System.out.println(test.arraylist.toString()); new Thread(new MyRunnable(test)).start(); new Thread(new MyRunnable(test)).start(); System.out.println(arraylist.toString()); } } my questions are: 1\ why the new Thread(new MyRunnable(test)).start(); cause the error: Cannot make a static reference to the non-static type MyRunnable ? 2\ what is the static reference refer to right here? thx in advanced

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• Sorting in Lua, counting number of items

  - by Josh

  Two quick questions (I hope...) with the following code. The script below checks if a number is prime, and if not, returns all the factors for that number, otherwise it just returns that the number prime. Pay no attention to the zs. stuff in the script, for that is client specific and has no bearing on script functionality. The script itself works almost wonderfully, except for two minor details - the first being the factor list doesn't return itself sorted... that is, for 24, it'd return 1, 2, 12, 3, 8, 4, 6, and 24 instead of 1, 2, 3, 4, 6, 8, 12, and 24. I can't print it as a table, so it does need to be returned as a list. If it has to be sorted as a table first THEN turned into a list, I can deal with that. All that matters is the end result being the list. The other detail is that I need to check if there are only two numbers in the list or more. If there are only two numbers, it's a prime (1 and the number). The current way I have it does not work. Is there a way to accomplish this? I appreciate all the help! function get_all_factors(number) local factors = 1 for possible_factor=2, math.sqrt(number), 1 do local remainder = number%possible_factor if remainder == 0 then local factor, factor_pair = possible_factor, number/possible_factor factors = factors .. ", " .. factor if factor ~= factor_pair then factors = factors .. ", " .. factor_pair end end end factors = factors .. ", and " .. number return factors end local allfactors = get_all_factors(zs.param(1)) if zs.func.numitems(allfactors)==2 then return zs.param(1) .. " is prime." else return zs.param(1) .. " is not prime, and its factors are: " .. allfactors end

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• Attempted GCF app for Android

  - by Aaron

  I am new to Android and am trying to create a very basic app that calculates and displays the GCF of two numbers entered by the user. Here is a copy of my GCF.java: package com.example.GCF; import java.util.Arrays; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; public class GCF extends Activity { private TextView mAnswer; private EditText mA, mB; private Button ok; private String A, B; private int iA, iB; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mA = (EditText) findViewById(R.id.entry); mB = (EditText) findViewById(R.id.entry1); ok = (Button) findViewById(R.id.ok); mAnswer = (TextView) findViewById(R.id.answer1); ok.setOnClickListener(new OnClickListener() { public void onClick(View v) { A = mA.getText().toString(); B = mB.getText().toString(); } }); // the String to int conversion happens here iA = Integer.parseInt(A.trim()); iB = Integer.parseInt(B.trim()); while (iA != iB) { int[] nums={ iA, iB, Math.abs(iA-iB) }; Arrays.sort(nums); iA=nums[0]; iB=nums[1]; } updateDisplay(); } private void updateDisplay() { mAnswer.setText( new StringBuilder().append(iA)); } } Any Suggestions? Thank you!

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• Reading input files in FORTRAN

  - by lollygagger

  Purpose: Create a program that takes two separate files, opens and reads them, assigns their contents to arrays, do some math with those arrays, create a new array with product numbers, print to a new file. Simple enough right? My input files have comment characters at the beginning. One trouble is, they are '#' which are comment characters for most plotting programs, but not FORTRAN. What is a simple way to tell the computer not to look at these characters? Since I have no previous FORTRAN experience, I am plowing through this with two test files. Here is what I have so far: PROGRAM gain IMPLICIT NONE REAL, DIMENSION (1:4, 1:8) :: X, Y, Z OPEN(1, FILE='test.out', & STATUS='OLD', ACTION='READ') ! opens the first file READ(1,*), X OPEN(2, FILE='test2.out', & STATUS='OLD', ACTION='READ') ! opens the second file READ(2,*), Y PRINT*, X, Y Z = X*Y ! PRINT*, Z OPEN(3, FILE='test3.out', STATUS='NEW', ACTION='WRITE') !creates a new file WRITE(3,*), Z CLOSE(1) CLOSE(2) CLOSE(3) END PROGRAM PS. Please do not overwhelm me with a bunch of code monkey gobblety gook. I am a total programming novice. I do not understand all the lingo, that is why I came here instead of searching for help in existing websites. Thanks.

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• Purpose of singletons in programming

  - by thecoshman

  This is admittedly a rather loose question. My current understanding of singletons is that they are a class that you set up in such a way that only one instance is ever created. This sounds a lot like a static class to me. The main differnce being that with a static class you don't / can't instance it, you just use it such as Math.pi(). With a singletong class, you would still need to do something like singleton mySingleton = new singleton(); mysingleton.set_name("foo"); singleton otherSingleton = new singleton(); // correct me if i am wrong, but mysingleton == othersingleton right now, yes? // this the following should happen? otherSingleston.set_name("bar"); mysingleton.report_name(); // will output "bar" won't it? Please note, I am asking this language independently, more about the concept. So I am not so worried about actually how to coed such a class, but more why you would wan't to and what thing you would need to consider.

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• Drawing line graphics leads Flash to spiral out of control!

  - by drpepper

  Hi, I'm having problems with some AS3 code that simply draws on a Sprite's Graphics object. The drawing happens as part of a larger procedure called on every ENTER_FRAME event of the stage. Flash neither crashes nor returns an error. Instead, it starts running at 100% CPU and grabs all the memory that it can, until I kill the process manually or my computer buckles under the pressure when it gets up to around 2-3 GB. This will happen at a random time, and without any noticiple slowdown beforehand. WTF? Has anyone seen anything like this? PS: I used to do the drawing within a MOUSE_MOVE event handler, which brought this problem on even faster. PPS: I'm developing on Linux, but reproduced the same problem on Windows. UPDATE: You asked for some code, so here we are. The drawing function looks like this: public static function drawDashedLine(i_graphics : Graphics, i_from : Point, i_to : Point, i_on : Number, i_off : Number) : void { const vecLength : Number = Point.distance(i_from, i_to); i_graphics.moveTo(i_from.x, i_from.y); var dist : Number = 0; var lineIsOn : Boolean = true; while(dist < vecLength) { dist = Math.min(vecLength, dist + (lineIsOn ? i_on : i_off)); const p : Point = Point.interpolate(i_from, i_to, 1 - dist / vecLength); if(lineIsOn) i_graphics.lineTo(p.x, p.y); else i_graphics.moveTo(p.x, p.y); lineIsOn = !lineIsOn; } } and is called like this (m_graphicsLayer is a Sprite): m_graphicsLayer.graphics.clear(); if (m_destinationPoint) { m_graphicsLayer.graphics.lineStyle(2, m_fixedAim ? 0xff0000 : 0x333333, 1); drawDashedLine(m_graphicsLayer.graphics, m_initialPos, m_destinationPoint, 10, 10); }

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• What is a good use case for static import of methods?

  - by Miserable Variable

  Just got a review comment that my static import of the method was not a good idea. The static import was of a method from a DA class, which has mostly static methods. So in middle of the business logic I had a da activity that apparently seemed to belong to the current class: import static some.package.DA.*; class BusinessObject { void someMethod() { .... save(this); } } The reviewer was not keen that I change the code and I didn't but I do kind of agree with him. One reason given for not static-importing was it was confusing where the method was defined, it wasn't in the current class and not in any superclass so it too some time to identify its definition (the web based review system does not have clickable links like IDE :-) I don't really think this matters, static-imports are still quite new and soon we will all get used to locating them. But the other reason, the one I agree with, is that an unqualified method call seems to belong to current object and should not jump contexts. But if it really did belong, it would make sense to extend that super class. So, when does it make sense to static import methods? When have you done it? Did/do you like the way the unqualified calls look? EDIT: The popular opinion seems to be that static-import methods if nobody is going to confuse them as methods of the current class. For example methods from java.lang.Math and java.awt.Color. But if abs and getAlpha are not ambiguous I don't see why readEmployee is. As in lot of programming choices, I think this too is a personal preference thing. Thanks for your response guys, I am closing the question.

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• returning a pointed to an object within a std::vector

  - by memC

  I have a very basic question on returning a reference to an element of a vector . There is a vector vec that stores instances of class Foo. I want to access an element from this vector . ( don't want to use the vector index) . How should I code the method getFoo here? #include<vector> #include<stdio.h> #include<iostream> #include<math.h> using namespace std; class Foo { public: Foo(){}; ~Foo(){}; }; class B { public: vector<Foo> vec; Foo* getFoo(); B(){}; ~B(){}; }; Foo* B::getFoo(){ int i; vec.push_back(Foo()); i = vec.size() - 1; // how to return a pointer to vec[i] ?? return vec.at(i); }; int main(){ B b; b = B(); int i = 0; for (i = 0; i < 5; i ++){ b.getFoo(); } return 0; }

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• graph and all pairs shortest path in java

  - by Sandra

  I am writing a java program using Flyod-Warshall algorithm “All pairs shortest path”. I have written the following : a0 is the adjacency matrix of my graph, but has infinity instead of 0. vList is the list of vertexes and the cost for each edge is 1. Path[i][j] = k+1 means for going from I to j you first go to k then j int[][] path = new int[size][size]; for(int i = 0; i<path.length;i++) { for(int j = 0; j<path.length; j++) { if(adjM[i][j]==1) path[i][j]=j+1; } } //*************** for (int k = 0; k < vList.size(); k++) for (int i = 0; i < vList.size(); i++) for (int j = 0; j < vList.size(); j++) { if (a0[i][j]>a0[i][k]+ a0[k][j]) path[i][j] = k + 1; a0[i][j] = Math.min(a0[i][j], a0[i][k] + a0[k][j]); } After running this code, in the result a0 is correct, but path is not correct and I don’t know why!. Would you please help me?

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• How to make paging start from 1 instead of 0 in ASP.NET MVC

  - by ssx

  I used the paging example of the Nerddinner tutorial. But I also wanted to add page Numbers, somehting like that: <<< 1 2 3 4 5 6 The code below works if i start my paging from 0, but not from 1. How can I fix this ? Here is my code: PaginatedList.cs public class PaginatedList<T> : List<T> { public int PageIndex { get; private set; } public int PageSize { get; private set; } public int TotalCount { get; private set; } public int TotalPages { get; private set; } public PaginatedList(IQueryable<T> source, int pageIndex, int pageSize) { PageIndex = pageIndex; PageSize = pageSize; TotalCount = source.Count(); TotalPages = (int) Math.Ceiling(TotalCount / (double)PageSize); this.AddRange(source.Skip(PageIndex * PageSize).Take(PageSize)); } public bool HasPreviousPage { get { return (PageIndex > 0); } } public bool HasNextPage { get { return (PageIndex+1 < TotalPages); } } } UserController.cs public ActionResult List(int? page) { const int pageSize = 20; IUserRepository userRepository = new UserRepository(); IQueryable<User> listUsers = userRepository.GetAll(); PaginatedList<User> paginatedUsers = new PaginatedList<User>(listUsers, page ?? 0, pageSize); return View(paginatedUsers); } List.cshtml @if (Model.HasPreviousPage) { @Html.RouteLink(" Previous ", "PaginatedUsers", new { page = (Model.PageIndex - 1) }) } @for (int i = 1; i <= Model.TotalPages; i++) { @Html.RouteLink(@i.ToString(), "PaginatedUsers", new { page = (@i ) }) } @if (Model.HasNextPage) { @Html.RouteLink(" Next ", "PaginatedUsers", new { page = (Model.PageIndex + 1) }) }

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• How to map string keys to unique integer IDs?

  - by Marek

  I have some data that comes regularily as a dump from a data souce with a string natural key that is long (up to 60 characters) and not relevant to the end user. I am using this key in a url. This makes urls too long and user unfriendly. I would like to transform the string keys into integers with the following requirements: The source dataset will change over time. The ID should be: non negative integer unique and constant even if the set of input keys changes preferrably reversible back to key (not a strong requirement) The database is rebuilt from scratch every time so I can not remember the already assigned IDs and match the new data set to existing IDs and generate sequential IDs for the added keys. There are currently around 30000 distinct keys and the set is constantly growing. How to implement a function that will map string keys to integer IDs? What I have thought about: 1. Built-in string.GetHashCode: ID(key) = Math.Abs(key.GetHashCode()) is not guaranteed to be unique (not reversible) 1.1 "Re-hashing" the built-in GetHashCode until a unique ID is generated to prevent collisions. existing IDs may change if something colliding is added to the beginning of the input data set 2. a perfect hashing function I am not sure if this can generate constant IDs if the set of inputs changes (not reversible) 3. translate to base 36/64/?? does not shorten the long keys enough What are the other options?

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• segmentation fault when using pointer to pointer

  - by user3697730

  I had been trying to use a pointer to pointer in a function,but is seems that I am not doing the memory allocation correctly... My code is: #include<stdio.h> #include<math.h> #include<ctype.h> #include<stdlib.h> #include<string.h> struct list{ int data; struct list *next; }; void abc (struct list **l,struct list **l2) { *l2=NULL; l2=(struct list**)malloc( sizeof(struct list*)); (*l)->data=12; printf("%d",(*l)->data); (*l2)->next=*l2; } int main() { struct list *l,*l2; abc(&l,&l2); system("pause"); return(0); } This code compiles,but I cannot run thw program..I get a segmentation fault..What should I do?Any help would be appreciated!

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• Is it okay to rely on javascript for menu layout?

  - by Ryan

  I have a website template where I do not know the number of menu items or the size of the menu items that will be required. The js below works exactly the way I want it to, however this is the most js I've every written. Are there any disadvantages or potential problems with this method that I'm not aware of because I'm a js beginner? I'm currently manually setting the padding for each site. Thank you! var width_of_text = 0; var number_of_li = 0; // measure the width of each <li> and add it to the total with, increment li counter $('li').each(function() { width_of_text += $(this).width(); number_of_li++; }); // calculate the space between <li>'s so the space is equal var padding = Math.floor((900 - width_of_text)/(number_of_li - 1)); // add the padding the all but the first <li> $('li').each(function(index) { if (index !== 0) { $(this).css("padding-left", padding); } });

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• How would you update 100+ variables if something is changed in a different class?

  - by N. Lucas

  I have a class Grid which produces a graph paper like grid on in the drawing area. I then have 5 other classes for different shapes to draw with; Line, Polygon, Ellipse, Curve, Arc Now, these 5 classes use an instance of Grid because Grid has a resolution and a scale. Inside Grid I have: public function set resolution(x:Number):void { _gap = (modBy10(x) / 10); _scale = (modBy10(x) / (this.resolution * _scale)); draw(); } public function get resolution():Number { return (_gap * 10); } public function set scale(x:Number):void { _scale = (this.resolution / x); } public function get scale():Number { return _scale; } /**/ public function scaleLength(x:Number):Number { return (x * this.scale); } public function scaleLengthDown(x:Number):Number { return (x / this.scale); } public function scaleArea(x:Number):Number { return (x / Math.pow(this.scale, 2)); } I'm just lost for a solution on how to update every instance of my 5 drawing classes when Grid is changed. For instance, Polygon is made up of multiple instances of Line, Line(length, angle) where "length" is in either in, ft, cm, or m. If the user wishes to change the scale from say 10ft per 100px resolution.. Is there an easier way than re-drawing every Line inside Polygon?

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• How to break out from nested doseqs

  - by fizbin

  Hi, I have a question regarding nested doseq loops. In the start function, once I find an answer I set the atom to true, so that the outer loop validation with :while fails. However it seems that it doesn't break it, and the loops keep on going. What's wrong with it? I am also quite confused with the usage of atoms, refs, agents (Why do they have different names for the update functions when then the mechanism is almost the same?) etc. Is it okay to use an atom in this situation as a flag? Obviously I need a a variable like object to store a state. (def pentagonal-list (map (fn [a] (/ (* a (dec (* 3 a))) 2)) (iterate inc 1))) (def found (atom false)) (defn pentagonal? [a] (let [y (/ (inc (Math/sqrt (inc (* 24 a)))) 6) x (mod (* 10 y) 10)] (if (zero? x) true false))) (defn both-pent? [a b] (let [sum (+ b a) diff (- a b)] (if (and (pentagonal? sum) (pentagonal? diff)) true false))) (defn start [] (doseq [x pentagonal-list :while (false? @found)] (doseq [y pentagonal-list :while (<= y x)] (if (both-pent? x y) (do (reset! found true) (println (- x y)))))))

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