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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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  • How to display buttons after enterframe event is over in Corona?

    - by user1463542
    I am trying to display two buttons called countd_again and main_menu after my enterframe event is over. I can't see those buttons after enterframe event is over,though. Can you check my code,please? And also i want to add new addListener for the buttons using director and scene. module(..., package.seeall) function new() local localGroup = display.newGroup(); display.setStatusBar(display.HiddenStatusBar) local background = display.newImage("background.png") start=os.time() cnt=1 local countd_again = display.newImage("yeniden.png") countd_again.x=100 countd_again.y=100 countd_again.isVisible= false; countd_again.alpha=0; countd_again.scene="helloWorld"; local main_menu= display.newImage("anamenu.png") main_menu.x=100 main_menu.y=300 main_menu.isVisible=false; main_menu.alpha=0; main_menu.scene="helloWorld" -- listener function local function onEveryFrame( event ) if (cnt~=0) then cnt= 3-(os.time()-start) minute = math.floor(cnt/60) second=cnt%60 --print(minute,second) minTxt=display.newText(minute,50,50,nil,100) secTxt=display.newText(second,250,50,nil,100) transition.to(minTxt, {time=100, alpha=0}) transition.to(secTxt,{time=100, alpha=0}) else Runtime: removeEventListener("enterFrame",onEveryFrame) countd_again.isVisible=true; main_menu.isVisible=true; transition.to(countd_again,{time=500,alpha=1}); transition.to(main_menu,{time=500,alpha=1}); countd_again: addEventListener("touch", changeScene) main_menu: addEventListener("touch", changeScene) end end -- assign the above function as an "enterFrame" listener Runtime:addEventListener( "enterFrame", onEveryFrame ) function changeScene(e) if(e.phase=="ended") then director:changeScene(e.target.scene); end end countd_again: addEventListener("touch", changeScene) main_menu: addEventListener("touch", changeScene) localGroup: insert(countd_again) localGroup:insert(main_menu) localGroup:insert(background) return localGroup; end

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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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  • 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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  • 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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  • 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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  • Using "from __future__ import division" in my program, but it isn't loaded with my program

    - by Sara Fauzia
    I wrote the following program in Python 2 to do Newton's method computations for my math problem set, and while it works perfectly, for reasons unbeknownst to me, when I initially load it in ipython with %run -i NewtonsMethodMultivariate.py, the Python 3 division is not imported. I know this because after I load my Python program, entering x**(3/4) gives "1". After manually importing the new division, then x**(3/4) remains x**(3/4), as expected. Why is this? # coding: utf-8 from __future__ import division from sympy import symbols, Matrix, zeros x, y = symbols('x y') X = Matrix([[x],[y]]) tol = 1e-3 def roots(h,a): def F(s): return h.subs({x: s[0,0], y: s[1,0]}) def D(s): return h.jacobian(X).subs({x: s[0,0], y: s[1,0]}) if F(a) == zeros(2)[:,0]: return a else: while (F(a)).norm() > tol: a = a - ((D(a))**(-1))*F(a) print a.evalf(10) I would use Python 3 to avoid this issue, but my Linux distribution only ships SymPy for Python 2. Thanks to the help anyone can provide. Also, in case anyone was wondering, I haven't yet generalized this script for nxn Jacobians, and only had to deal with 2x2 in my problem set. Additionally, I'm slicing the 2x2 zero matrix instead of using the command zeros(2,1) because SymPy 0.7.1, installed on my machine, complains that "zeros() takes exactly one argument", though the wiki suggests otherwise. Maybe this command is only for the git version.

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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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  • 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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  • loop is cut one element of the array

    - by Walaa
    The problem is : Write a program that reads a number n and then declares an array of n elements. The program then fills the array with the first n numbers, where each number is two to the power of the previous. Finally, display array’s contents. My code : import java.util.*; public class Q1 { static Scanner scan = new Scanner (System.in); public static void main(String args [] ) { int num; int i = 0; System.out.println("Enter a number :"); num = scan.nextInt(); double [] a=new double[num]; a[0]= num ; for ( ;i<=a.length-1 ; i++) { a[i+1] = Math.pow(2,a[i]); System.out.println((int)(a[i]) ); } } } The error is : ----jGRASP exec: java Q1 Enter a number : 4 4 16 65536 Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4 at Q1.main(Q1.java:16) ----jGRASP wedge2: exit code for process is 1. why it says that? And the number by user printed twice!

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  • My method is too specific. How can I make it more generic?

    - by EricBoersma
    I have a class, the outline of which is basically listed below. import org.apache.commons.math.stat.Frequency; public class WebUsageLog { private Collection<LogLine> logLines; private Collection<Date> dates; WebUsageLog() { this.logLines = new ArrayList<LogLine>(); this.dates = new ArrayList<Date>(); } SortedMap<Double, String> getFrequencyOfVisitedSites() { SortedMap<Double, String> frequencyMap = new TreeMap<Double, String>(Collections.reverseOrder()); //we reverse order to sort from the highest percentage to the lowest. Collection<String> domains = new HashSet<String>(); Frequency freq = new Frequency(); for (LogLine line : this.logLines) { freq.addValue(line.getVisitedDomain()); domains.add(line.getVisitedDomain()); } for (String domain : domains) { frequencyMap.put(freq.getPct(domain), domain); } return frequencyMap; } } The intention of this application is to allow our Human Resources folks to be able to view Web Usage Logs we send to them. However, I'm sure that over time, I'd like to be able to offer the option to view not only the frequency of visited sites, but also other members of LogLine (things like the frequency of assigned categories, accessed types [text/html, img/jpeg, etc...] filter verdicts, and so on). Ideally, I'd like to avoid writing individual methods for compilation of data for each of those types, and they could each end up looking nearly identical to the getFrequencyOfVisitedSites() method. So, my question is twofold: first, can you see anywhere where this method should be improved, from a mechanical standpoint? And secondly, how would you make this method more generic, so that it might be able to handle an arbitrary set of data?

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  • [C++] Trouble declaring and recognizing global functions

    - by Sarah
    I've created some mathematical functions that will be used in main() and by member functions in multiple host classes. I was thinking it would be easiest to make these math functions global in scope, but I'm not sure how to do this. I've currently put all the functions in a file called Rdraws.cpp, with the prototypes in Rdraws.h. Even with all the #includes and externs, I'm getting a "symbol not found" error at the first function call in main(). Here's what I have: // Rdraws.cpp #include <cstdlib> using namespace std; #include <cmath> #include "Rdraws.h" #include "rng.h" extern RNG rgen // this is the PRNG used in the simulation; global scope void rmultinom( double p_trans[], int numTrials, int numTrans, int numEachTrans[] ) { // function 1 def } void rmultinom( const double p_trans[], const int numTrials, int numTrans, int numEachTrans[]) { // function 2 def } int rbinom( int nTrials, double pLeaving ) { // function 3 def } // Rdraws.h #ifndef RDRAWS #define RDRAWS void rmultinom( double[], int, int, int[] ); void rmultinom( const double[], const int, int, int[] ); int rbinom( int, double ); #endif // main.cpp ... #include "Rdraws.h" ... extern void rmultinom(double p_trans[], int numTrials, int numTrans, int numEachTrans[]); extern void rmultinom(const double p_trans[], const int numTrials, int numTrans, int numEachTrans[]); extern int rbinom( int n, double p ); ... int main() { ... } I'm pretty new to programming. If there's a dramatically smarter way to do this, I'd love to know.

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  • jQuery .height() property not working

    - by Andrew
    I'm attempting to get the height of an element using jQuery, but am receiving some unexpected results. Here's the code: $(function() { var contentheight = $('#subpage-content-small').height; alert(contentheight); }); Where #subpage-content-small has these CSS properties: #subpage-content-small { width: 400px; float: left; margin: 30px 10px 0 0; padding-bottom: 45px; } What I'm getting as an output for my alert is the following: function (f) { var e = this[0]; if (!e) { return f == null ? null : this; } if (c.isFunction(f)) { return this.each(function (j) {var i = c(this);i[d](f.call(this, j, i[d]()));}); } return "scrollTo" in e && e.document ? e.document.compatMode === "CSS1Compat" && e.document.documentElement["client" + b] || e.document.body["client" + b] : e.nodeType === 9 ? Math.max(e.documentElement["client" + b], e.body["scroll" + b], e.documentElement["scroll" + b], e.body["offset" + b], e.documentElement["offset" + b]) : f === w ? c.css(e, d) : this.css(d, typeof f === "string" ? f : f + "px"); } Any idea why I'm getting this as opposed to an integer of the height? Thanks in advance!

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  • Looking for an appropriate design pattern

    - by user1066015
    I have a game that tracks user stats after every match, such as how far they travelled, how many times they attacked, how far they fell, etc, and my current implementations looks somewhat as follows (simplified version): Class Player{ int id; public Player(){ int id = Math.random()*100000; PlayerData.players.put(id,new PlayerData()); } public void jump(){ //Logic to make the user jump //... //call the playerManager PlayerManager.jump(this); } public void attack(Player target){ //logic to attack the player //... //call the player manager PlayerManager.attack(this,target); } } Class PlayerData{ public static HashMap<int, PlayerData> players = new HashMap<int,PlayerData>(); int id; int timesJumped; int timesAttacked; } public void incrementJumped(){ timesJumped++; } public void incrementAttacked(){ timesAttacked++; } } Class PlayerManager{ public static void jump(Player player){ players.get(player.getId()).incrementJumped(); } public void incrementAttacked(Player player, Player target){ players.get(player.getId()).incrementAttacked(); } } So I have a PlayerData class which holds all of the statistics, and brings it out of the player class because it isn't part of the player logic. Then I have PlayerManager, which would be on the server, and that controls the interactions between players (a lot of the logic that does that is excluded so I could keep this simple). I put the calls to the PlayerData class in the Manager class because sometimes you have to do certain checks between players, for instance if the attack actually hits, then you increment "attackHits". The main problem (in my opinion, correct me if I'm wrong) is that this is not very extensible. I will have to touch the PlayerData class if I want to keep track of a new stat, by adding methods and fields, and then I have to potentially add more methods to my PlayerManager, so it isn't very modulized. If there is an improvement to this that you would recommend, I would be very appreciative. Thanks.

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  • HLSL - Combining textures

    - by b34r
    Hi All, I'm trying to combine two textures in HLSL - specifically, I want to take the alpha values from a base image, and the color data from an overlay image. My pixel shader for this looks like this: float4 PixelShaderFunction(VertexOut input) : COLOR0 { float4 baseColor = tex2D( BaseSampler, input.baseCoords.xy ).rgba; float4 overlayColor = tex2D( OverlaySampler, input.overlayCoords.xy ).rgba; float4 color; color.r = overlayColor.r; color.g = overlayColor.g; color.b = overlayColor.b; color.a = baseColor.a; return color.rgba; } and my blend state looks like this: BlendState bs = new BlendState(); bs.AlphaSourceBlend = Blend.SourceAlpha; bs.AlphaDestinationBlend = Blend.DestinationAlpha; bs.ColorSourceBlend = Blend.SourceColor; bs.ColorDestinationBlend = Blend.DestinationColor; What this leaves me with is a washed out version of what should be the overlay color. I've tried numerous permutations of the BlendState settings, and played with the pixel shader math quite a bit, but to no avail. Can anyone point me in the right direction? Thanks in advance =)

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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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  • 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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  • A good way to write unit tests

    - by bobobobo
    So, I previously wasn't really in the practice of writing unit tests - now I kind of am and I need to check if I'm on the right track. Say you have a class that deals with math computations. class Vector3 { public: // Yes, public. float x,y,z ; // ... ctors ... } ; Vector3 operator+( const Vector3& a, const Vector3 &b ) { return Vector3( a.x + b.y /* oops!! hence the need for unit testing.. */, a.y + b.y, a.z + b.z ) ; } There are 2 ways I can really think of to do a unit test on a Vector class: 1) Hand-solve some problems, then hard code the numbers into the unit test and pass only if equal to your hand and hard-coded result bool UnitTest_ClassVector3_operatorPlus() { Vector3 a( 2, 3, 4 ) ; Vector3 b( 5, 6, 7 ) ; Vector3 result = a + b ; // "expected" is computed outside of computer, and // hard coded here. For more complicated operations like // arbitrary axis rotation this takes a bit of paperwork, // but only the final result will ever be entered here. Vector3 expected( 7, 9, 11 ) ; if( result.isNear( expected ) ) return PASS ; else return FAIL ; } 2) Rewrite the computation code very carefully inside the unit test. bool UnitTest_ClassVector3_operatorPlus() { Vector3 a( 2, 3, 4 ) ; Vector3 b( 5, 6, 7 ) ; Vector3 result = a + b ; // "expected" is computed HERE. This // means all you've done is coded the // same thing twice, hopefully not having // repeated the same mistake again Vector3 expected( 2 + 5, 6 + 3, 4 + 7 ) ; if( result.isNear( expected ) ) return PASS ; else return FAIL ; } Or is there another way to do something like this?

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  • Top n items in a List ( including duplicates )

    - by Krishnan
    Trying to find an efficient way to obtain the top N items in a very large list, possibly containing duplicates. I first tried sorting & slicing, which works. But this seems unnnecessary. You shouldn't need to sort a very large list if you just want the top 20 members. So I wrote a recursive routine which builds the top-n list. This also works, but is very much slower than the non-recursive one! Question: Which is my second routine (elite2) so much slower than elite, and how do I make it faster ? My code is attached below. Thanks. import scala.collection.SeqView import scala.math.min object X { def elite(s: SeqView[Int, List[Int]], k:Int):List[Int] = { s.sorted.reverse.force.slice(0,min(k,s.size)) } def elite2(s: SeqView[Int, List[Int]], k:Int, s2:List[Int]=Nil):List[Int] = { if( k == 0 || s.size == 0) s2.reverse else { val m = s.max val parts = s.force.partition(_==m) val whole = if( parts._1.size > 1) parts._1.tail:::parts._2 else parts._2 elite2( whole.view, k-1, m::s2 ) } } def main(args:Array[String]) = { val N = 1000000/3 val x = List(N to 1 by -1).flatten.map(x=>List(x,x,x)).flatten.view println(elite2(x,20)) println(elite(x,20)) } }

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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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  • c++ expected constant expression

    - by cpp
    #include <iostream> #include <fstream> #include <cmath> #include <math.h> #include <iomanip> using std::ifstream; using namespace std; int main (void) { int count=0; float sum=0; float maximum=-1000000; float sumOfX; float sumOfY; int size; int negativeY=0; int positiveX=0; int negativeX=0; ifstream points; //the points to be imported from file //points.open( "data.dat"); //points>>size; //cout<<size<<endl; size=100; float x[size][2]; while (count<size) { points>>(x[count][0]); //cout<<"x= "<<(x[count][0])<<" ";//read in x value points>>(x[count][1]); //cout<<"y= "<<(x[count][1])<<endl;//read in y value count++; } This program is giving me expected constant expression error on the line where I declare float x[size][2]. why?

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  • Centering Divisions Around Zero

    - by Mark
    I'm trying to create something that sort of resembles a histogram. I'm trying to create buckets from an array. Suppose I have a random array doubles between -10 and 10; this is very simplified. I then want to specify a center point, in this case 0 and the number of buckets. If I want 4 buckets the division would be -10 to -5, -5 to 0, 0 to 5 and 5 to 10. Not that complicated right. Now if I change the min and max to -12 and -9 and as for 4 divisions its more complicated. I either want a division at -3 and 3; it is centered around 0 ; or one at -6 to 0 and 0 to 6. Its not that hard to find the division size = Math.Ceiling((Abs(Max) + Abs(Min)) / Divisions) Then you would basically have an if statement to determine whether you want it centered on 0 or on an edge. You then iterate out from either 0 or DivisionSize/2 depending on the situation. You may not ALWAYS end up with the specified number of divisions but it will be close. Then you iterate through the array and increment the bin count. Does this seem like a good way to go about this? This method would surely work but it does not seem to be the most elegant. I'm curious as to whether the creation of the bins and the counting from the list could be done in a clever class with linq in a more elegant way? Something like creating the bins and then having each bin be a property {get;} that returns list.Count(x=> x >= Lower && x < Upper).

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  • How do I call C++/CLI (.NET) DLLs from standard, unmanaged non-.NET applications?

    - by tronjohnson
    In the unmanaged world, I was able to write a __declspec(dllexport) or, alternatively, use a .DEF file to expose a function to be able to call a DLL. (Because of name mangling in C++ for the __stdcall, I put aliases into the .DEF file so certain applications could re-use certain exported DLL functions.) Now, I am interested in being able to expose a single entry-point function from a .NET assembly, in unmanaged-fashion, but have it enter into .NET-style functions within the DLL. Is this possible, in a simple and straight-forward fashion? What I have is a third-party program that I have extended through DLLs (plugins) that implement some complex mathematics. However, the third-party program has no means for me to visualize the calculations. I want to somehow take these pre-written math functions, compile them into a separate DLL (but using C++/CLI in .NET), but then add hooks to the functions so I can render what's going on under the hood in a .NET user control. I'm not sure how to blend the .NET stuff with the unmanaged stuff, or what to Google to accomplish this task. Specific suggestions with regard to the managed/unmanaged bridge, or alternative methods to accomplish the rendering in the manner I have described would be helpful. Thank you.

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  • Best way to import a pack or "system" of new classes??

    - by Joe Blow
    Here's an Advanced question for Advanced developers. So I've written a largish "subsystem". It is essentially a UIViewController called CleverViewController which is a UIViewController. Now, there are a large number of supporting classes (about ten) that do the hard work: perform math functions, image processing, purely logical functions, build images or what have you with thousands of lines of code. (To do this, I simply started a new XCode project / app "Scratchpad" which does little other than load and launch the CleverViewController. So currently it works as an app, which launches CleverViewController. The ten or so classes I mention that are part of the "subsystem" simply sit there in that project/app.) So now, we will use CleverViewController, the new technology generally, in various apps. (Or perhaps friends would want to use it, etc.) What's the best way to "do" this? Have I screwed everything up, and really it should just be ONE (pretty big) class rather than a dozen classes? (I could understand that then as I would simply add that new (big) class where needed, like adding any other class.) Do I have to make a "framework" like the Apple frameworks? (If so, what the hell are they, how do you do it, etc?!?) In fact, do you just have to lamely include all of the dozen classes and that's that (obviously perhaps putting them in a grouped subfolder). What about all the headers and so on? (Currently I just have the dozen includes in the pch file of the scratchpad project.) Shouldn't it be easy to "maintain" this "subsystem" separately and so on? I'm afraid I know nothing about this: if the answer is obvious, hit me over the head and let me know. Thank you for any info on this !

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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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