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  • Why won't C++ allow this default value

    - by nieldw
    Why won't GCC allow a default parameter here? template<class edgeDecor, class vertexDecor, bool dir> Graph<edgeDecor,int,dir> Graph<edgeDecor,vertexDecor,dir>::Dijkstra(vertex s, bool print = false) const { This is the output I get: graph.h:82: error: default argument given for parameter 2 of ‘Graph<edgeDecor, int, dir> Graph<edgeDecor, vertexDecor, dir>::Dijkstra(Vertex<edgeDecor, vertexDecor, dir>, bool)’ graph.h:36: error: after previous specification in ‘Graph<edgeDecor, int, dir> Graph<edgeDecor, vertexDecor, dir>::Dijkstra(Vertex<edgeDecor, vertexDecor, dir>, bool)’ Can anyone see why I'm getting this?

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  • Backtracking infinite loop

    - by Greenhorn
    This is Exercise 28.1.2 from HtDP. I've successfully implemented the neighbors function and all test cases pass. (define Graph (list (list 'A (list 'B 'E)) (list 'B (list 'E 'F)) (list 'C (list 'D)) (list 'D empty) (list 'E (list 'C 'F)) (list 'F (list 'D 'G)) (list 'G empty))) (define (first-line n alist) (cond [(symbol=? (first alist) n) alist] [else empty])) ;; returns empty if node is not in graph (define (neighbors n g) (cond [(empty? g) empty] [(cons? (first g)) (cond [(symbol=? (first (first g)) n) (first-line n (first g))] [else (neighbors n (rest g))])])) ; test cases (equal? (neighbors 'A Graph) (list 'A (list 'B 'E))) (equal? (neighbors 'B Graph) (list 'B (list 'E 'F))) (equal? (neighbors 'C Graph) (list 'C (list 'D))) (equal? (neighbors 'D Graph) (list 'D empty)) (equal? (neighbors 'E Graph) (list 'E (list 'C 'F))) (equal? (neighbors 'F Graph) (list 'F (list 'D 'G))) (equal? (neighbors 'G Graph) (list 'G empty)) (equal? (neighbors 'H Graph) empty) The problem comes when I copy-paste the code from Figure 77 of the text. It is supposed to determine whether a destination node is reachable from an origin node. However it appears that the code goes into an infinite loop except for the most trivial case where the origin and destination nodes are the same. ;; find-route : node node graph -> (listof node) or false ;; to create a path from origination to destination in G ;; if there is no path, the function produces false (define (find-route origination destination G) (cond [(symbol=? origination destination) (list destination)] [else (local ((define possible-route (find-route/list (neighbors origination G) destination G))) (cond [(boolean? possible-route) false] [else (cons origination possible-route)]))])) ;; find-route/list : (listof node) node graph -> (listof node) or false ;; to create a path from some node on lo-Os to D ;; if there is no path, the function produces false (define (find-route/list lo-Os D G) (cond [(empty? lo-Os) false] [else (local ((define possible-route (find-route (first lo-Os) D G))) (cond [(boolean? possible-route) (find-route/list (rest lo-Os) D G)] [else possible-route]))])) Does the problem lie in my code? Thank you.

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  • How can I plot a time series graph with Perl?

    - by Jazz
    I have some data from a database (SQLite), mapping a value (an integer) to a date. A date is a string with this format: YYYY-MM-DD hh:mm. The dates are not uniformly distributed. I want do draw a line graph with the dates on X and the values on Y. What is the easiest way to do this with Perl? I tried DBIx::Chart but I could not make it recognize my dates. I also tried GD::Graph, but as the documentation says: GD::Graph does not support numerical x axis the way it should. Data for X axes should be equally spaced

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  • What are real-world examples of Gradle's dependency graph?

    - by Michael Easter
    As noted in the documentation, Gradle uses a directed acyclic graph (DAG) to build a dependency graph. From my understanding, having separate cycles for evaluation and execution is a major feature for a build tool. e.g. The Gradle doc states that this enables some features that would otherwise be impossible. I'm interested in real-world examples that illustrate the power of this feature. What are some use-cases for which a dependency graph is important? I'm especially interested in personal stories from the field, whether with Gradle or a similarly equipped tool. I am making this 'community wiki' from the outset, as it will be difficult to assess a 'correct' answer.

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  • Why doesn't JFreeCharts correctly connect the points in my xy-line graph?

    - by Javajava
    /Each letter A,T,G,C represents a direction for the plot to graph. Specifically, “A” means move right, “T” is move down, “C” is move up, and “G” is move left. When the applet reads A,T,C, it plots the graph correctly. However, when I plot G, the graph is messed up. When I input "ACACACA," the graph is like a rising staircase. When I input "gtgtgt," the graph should look like a staircase, but it looks like a lightning bolt instead/ /This is all one code... i don't know why it's all split up like this:/ import java.applet.Applet; import java.awt.*; import java.awt.event.*; import java.util.Scanner.*; import java.jfree.chart.*; import java.jfree.data.xy.*; import java.jfree.chart.plot.PlotOrientation; public class If_Graph extends Applet implements ActionListener{ Panel panel; TextArea textarea, outputArea; Button move; String thetext; Scanner reader = new Scanner(System.in); String thetext2; int size,p,q; int x,y; public void init(){ setSize(500,500); //set size of applet panel = new Panel(); add(panel); setVisible(true); textarea= new TextArea(10,20); add(textarea); move=new Button("Graph"); move.addActionListener(this); add(move); } public void actionPerformed(ActionEvent e) { XYSeries series = new XYSeries("DNA Walk"); x= 0; y = 0; series.add(x,y); if(e.getSource() == move) { thetext=textarea.getText(); //the text is the DNA bases pasted thetext=thetext.replaceAll(" ",""); //removes spaces thetext2 = ""; for(int i=0; i<thetext.length(); i++) { char a = thetext.charAt(i); switch (a) { case 'A': //moves right x+=1; y+=0; series.add(x,y); break; case 'a': x+=1;y+=0; series.add(x,y); break; case 'C': //moves up x+=0; y+=1; series.add(x,y); break; case 'c': x+=0; y+=1; System.out.println(x + "," + y); series.add(x,y); break; case 'G': //move left x-=1; y+=0; series.add(x,y); System.out.println("G is: "+ x +"," +y); break; case 'g': x-=1; y+=0; System.out.println("g is: " +x + "," + y); series.add(x,y); break; case 'T': //move down x+=0; y-=1; series.add(x,y); System.out.println("T is: "+ x +"," +y); break; case 't': x+=0; y-=1; series.add(x,y); System.out.println("t is: "+ x +"," +y); break; default: // series.add(0,0); break; } } XYDataset xyDataset = new XYSeriesCollection(series); JFreeChart chart = ChartFactory.createXYLineChart ("DNA Random Walk", "", "", xyDataset, PlotOrientation.VERTICAL, true, true, false); ChartFrame frame1=new ChartFrame("DNA Random Walk",chart); frame1.setVisible(true); frame1.setSize(300,300); outputArea.setText(thetext2); } } }

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  • How do I plot a STOCK historical graph in android app?

    - by jer
    I wanted to plot a stock historical graph based on google finance in my android app . The problem is I can't find the api for just the stock chart alone and I must try to find another ways to do it. I thought of a way but don't know what whether it works the steps are as follows.. 1) get the details from csv file 2) read the csv file 3) plot the graph using the information of the csv file.(WHICH I DON'T KNOW HOW TO DO IT)! so if my steps above works , I would only want to know how to plot the graph.

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  • How to find the formula of best case and worst case of my algorithm?

    - by rachel7660
    I was given a task. Write an algorithm so that, the input of 2 lists of data, will have at least one in common. So, this is my algorithm: (I write the code in php) $arrayA = array('5', '6', '1', '2', '7'); $arrayB = array('9', '2', '1', '8', '3'); $arrayC = array(); foreach($arrayA as $val){ if(in_array($val, $arrayB)){ array_push($arrayC, $val); } } Thats my own algo, not sure if its a good one. So, based on my algorithm, how to find the formula of best case and worst case (big O)? Note: Please do let me know, if my algorithm is wrong. My goal is " input of 2 lists of data, will have at least one in common."

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  • How to raise CComponent event in Yii

    - by srigi
    Let's assume I have Component (say Graph like Yahoo Finance) rendered on the page. Component view template contains bunch of a_hrefs which I wanto to switch period in graph. I created Event and Event handler in Component. I have two questions: How to raise event on Graph Component via those a_hrefs (should they be part of Graph?)? How to redraw Graph without loosing curent page context (section, filter - specified as $_GET values)? My Graph Component look like this: Yii::import('zii.widgets.CPortlet'); class Graph extends CPortlet { private $_period; /* ********************** * * COMPONENT PROPERTIES * * ********************** */ public function getPeriod() { return $this-_period; } public function setPeriod($period) { $this-_period = $period; } /* ********************** * * GENERIC * * ********************** */ public function init() { parent::init(); // assign event handlers $this-onPeriodChange = array($this, 'handlePeriodChange'); } protected function renderContent() { $this-render('graph'); } /* ********************** * * EVENTS * * ********************** */ public function onPeriodChange($event) { $this-raiseEvent('onPeriodChange', $event); } /* ********************** * * EVENT HANDLERS * * ********************** */ public function handlePeriodChange($event) { // CODE } }

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  • Algorithm to rotate an image 90 degrees in place? (No extra memory)

    - by user9876
    In an embedded C app, I have a large image that I'd like to rotate by 90 degrees. Currently I use the well-known simple algorithm to do this. However, this algorithm requires me to make another copy of the image. I'd like to avoid allocating memory for a copy, I'd rather rotate it in-place. Since the image isn't square, this is tricky. Does anyone know of a suitable algorithm?

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  • python: os.system does not execute shell comand

    - by capoluca
    I need to execute shell command in python program (I have ubuntu). More specifically I want to create graph using graphviz in python script. My code is os.system("dot -Tpng graph.dot -o graph.png") It does not work, but if I just type dot -Tpng graph.dot -o graph.png in command line then everything is fine. Do you know what the problem? Thank you! Edit: Does not work means that nothing happens, there are no errors. Output from dot -v -Tpng graph.dot -o graph.png: dot - graphviz version 2.26.3 (20100126.1600) Activated plugin library: libgvplugin_pango.so.6 Using textlayout: textlayout:cairo Activated plugin library: libgvplugin_dot_layout.so.6 Using layout: dot:dot_layout Using render: cairo:cairo Using device: png:cairo:cairo The plugin configuration file: /usr/lib/graphviz/config6 was successfully loaded. render : cairo dot fig gd map ps svg tk vml vrml xdot layout : circo dot fdp neato nop nop1 nop2 osage patchwork sfdp twopi textlayout : textlayout device : canon cmap cmapx cmapx_np dot eps fig gd gd2 gif gv imap imap_np ismap jpe jpeg jpg pdf plain plain-ext png ps ps2 svg svgz tk vml vmlz vrml wbmp x11 xdot xlib loadimage : (lib) eps gd gd2 gif jpe jpeg jpg png ps svg

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  • So are we ever getting the technological singularity

    - by jsoldi
    I´m still waiting for an AI robot that will pass the Turing test. I keep going back to http://www.a-i.com/ and nothing. I don´t know much about AI but, did anyone ever tried to make a genetic algorithm whose evolution algorithm itself evolves? Or how about one whose algorithm that makes the genetic algorithm evolve, evolves? Or one whose genetic algorithm that makes the genetic algorithm that makes the genetic algorithm evolve, evolves? Or how about an algorithm that abstracts all this into a potentially infinitely deep tree of genetic evolution algorithms? Aren´t we just failing as programmers? And I don´t think we can blame the processors speed. If you make and application that simulates consciousness you will get a Nobel prize no matter how many hours it takes to respond to your questions. But nobody did it. It almost reminds me to Randi´s $1000000 paranormal challenge. As I keep going back to AI chat bots, they keep getting better at changing the subject on a way that seems natural. But if I tell them something like "if 'x' is 2 then whats two times 'x'?" then they don't have a clue what I'm talking about. And I don't think they need a whole human brain simulation to be able to answer to something like that. They don't need feelings or perception. This is just language and logics. I don't think my perception of the color red gives me the ability to understand that if 'x' is 2 then two times 'x' is 4. I'm sure we are just missing some elemental principle we cannot grasp because it's probably stuck behind our eyes. What do you think?

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  • Can I use a genetic algorithm for balancing character builds?

    - by Renan Malke Stigliani
    I'm starting to build a online PVP (duel like, one-on-one) game, where there is leveling, skill points, special attacks and all the common stuff. Since I have never done anything like this, I'm still thinking about the math behind the levels/skills/specials balance. So I thought a good way of testing the best builds/combos, would be to implement a Genetic Algorithm. It'd be like this: Generate a big group of random characters Make them fight, level them up accordingly to their victories(more XP)/losses(less XP) Mate the winners, crossing their builds, to try and make even better characters Add some more random chars, emulating new players Repeat the process for some time, or util I find some chars who can beat everyone's butt I could then play with the math and try to find better balances to make sure that the top x% of chars would be a mix of various build types. So, is it a good idea, or is there some other, easier method to do the balancing?

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  • What alternatives exist of how an agent can follow the path calculated by a path-finding algorithm?

    - by momboco
    What alternatives exist of how an agent can follow the path calculated by a path-finding algorithm? I've seen that the most easy form is go to one point and when the agent has reached this point, discard it and go to the next point. I think that this approach has problems when the game has physics with dynamic objects that can block the travel between point A and point B, then the agent is taken from his original trayectory and sometimes go to the last destiny point is not the most natural behavior. In the literature always I have read that the path is only a suggestion of where the agent has to go, but I don't know how this suggested path must be followed. Thanks.

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  • How important is it for a programmer to know how to implement a QuickSort/MergeSort algorithm from memory?

    - by John Smith
    I was reviewing my notes and stumbled across the implementation of different sorting algorithms. As I attempted to make sense of the implementation of QuickSort and MergeSort, it occurred to me that although I do programming for a living and consider myself decent at what I do, I have neither the photographic memory nor the sheer brainpower to implement those algorithms without relying on my notes. All I remembered is that some of those algorithms are stable and some are not. Some take O(nlog(n)) or O(n^2) time to complete. Some use more memory than others... I'd feel like I don't deserve this kind of job if it weren't because my position doesn't require that I use any sorting algorithm other than those found in standard APIs. I mean, how many of you have a programming position where it actually is essential that you can remember or come up with this kind of stuff on your own?

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  • What encryption algorithm/package should I use in a betting game?

    - by user299648
    I have a betting type site where I publish a number (between 0-100) that is encrypted. Then after a period of time, I would review what the number is and prove it with a key to decrypt the encrypted number to prove that I'm not cheating. I also want it to be easily verifiable by an average user. What encryption algorithm/technique/package should I use? I'm no expert on cryptography. There seems to be so many options out there and I'm not sure what to use. python friendly is a plus.

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  • How do you choose a programming/data structure/algorithm book?

    - by Fanatic23
    I really should not be mentioning the name of the book, but the first time I read it (during my under-grad days) I almost concluded that data structure was a bad course to pick. Which brings me to the question I am asking here. What makes a programming or data structure or algorithm book tick? Clearly, lucid explanation is one. But I also realize that organization of the material is very important and so is diagrams. What else? Some pointers would obviously help when I hang out in my neighborhood computer book shop the next time.

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  • Google new algorithm: My company have a 40 sites with different domains that some of their articles appears in my main website

    - by user5674576
    Hi, My company have a 40 sites with different domains that some of their articles appears in my main website with reference to their source. Our articles write by high level processionals in the field that they write about - we also pay them high salary. In recent google algorithm change my main site rating down very seriously. What should we do to restore company main site google rating? our solution and ideas that not working well: rel="canonical" to source website (we already have it before google change without results) meta "original-source" but not have rating influence (we already have it before google change without results) Edit:: maybe we should delete rel="canonical" from main website articles that refer to our other small websites (because this articles in main website not indexed in google)? Thanks in advance

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  • What data-structure/algorithm will allow me to send a list of key/value dictionaries using the least amount of bits?

    - by user12365
    I have server objects that have corresponding client objects. The data to be kept in sync is inside the server object's key/value dictionary. To keep the client objects in sync with the sever objects, I want the server to send the key/value dictionary every frame for each object. What data-structure/algorithm will allow me to send a list of key/value dictionaries using the least amount of bits? Bonus constraint 1: For each type of object, the values of some keys change more often than others. Bonus constraint 2: Memory usage on the server side is relatively expensive.

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  • What encryption algorithm/package should I use in a betting game type situation?

    - by user299648
    I have a betting type site where I publish a number (between 0-100) that is encrypted. Then after a period of time, I would review what the number is and prove it with a key to decrypt the encrypted number to prove that I'm not cheating. I also want it to be easily verifiable by an average user. What encryption algorithm/technique/package should I use? I'm no expert on cryptography. There seems to be so many options out there and I'm not sure what to use. python friendly is a plus.

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  • How do I implement graphs and graph algorithms in a functional programming language?

    - by brad
    Basically, I know how to create graph data structures and use Dijkstra's algorithm in programming languages where side effects are allowed. Typically, graph algorithms use a structure to mark certain nodes as 'visited', but this has side effects, which I'm trying to avoid. I can think of one way to implement this in a functional language, but it basically requires passing around large amounts of state to different functions, and I'm wondering if there is a more space-efficient solution.

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  • [Facebook Graph API - Android] I want to know the HTTPSConnection redirected to which URL?

    - by Mohammad Abdelaziz
    I am building an application that uses the Facebook Graph API. To get the access token I should send the following request https://graph.facebook.com/oauth/authorize? client_id=...& redirect_uri=http://www.example.com/callback It redirects to the redirect_uri with the code to be used as access token. How can I capture that the HttpsURLConnection is redirected and how to get the code? Is it possible or I need to have server that gets the access token?

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  • Why isn't my algorithm for find the biggest and smallest inputs working?

    - by Matt Ellen
    I have started a new job, and with it comes a new language: Ironpython. Thankfully a good language :D Before starting I got to grips with Python on the whole, but that was only a week's worth of learning. Now I'm writing actual code. I've been charged with writing an algorithm that finds the best input parameter to collect data with. The basic algorithm is (as I've been instructed): Set the input parameter to a good guess Start collecting data When data is available stop collecting find the highest point If the point before this (i.e. for the previous parameter value) was higher and the point before that was lower then we've found the max otherwise the input parameter is increased by the initial guess. goto 2 If the max is found then the min needs to be found. To do this the algorithm carries on increasing the input, but by 1/10 of the max, until the current point is greater than the previous point and the point before that is also greater. Once the min is found then the algorithm stops. Currently I have a simplified data generator outputting the sin of the input, so that I know that the min value should be PI and the max value should be PI/2 The main Python code looks like this (don't worry, this is just for my edification, I don't write real code like this): import sys sys.path.append(r"F:\Programming Source\C#\PythonHelp\PythonHelp\bin\Debug") import clr clr.AddReferenceToFile("PythonHelpClasses.dll") import PythonHelpClasses from PHCStruct import Helper from System import Math helper = Helper() def run(): b = PythonHelpClasses.Executor() a = PythonHelpClasses.HasAnEvent() b.Input = 0.0 helper.__init__() def AnEventHandler(e): b.Stop() h = helper h.lastLastVal, h.lastVal, h.currentVal = h.lastVal, h.currentVal, e.Number if h.lastLastVal < h.lastVal and h.currentVal < h.lastVal and h.NotPast90: h.NotPast90 = False h.bestInput = h.lastInput inputInc = 0.0 if h.NotPast90: inputInc = Math.PI/10.0 else: inputInc = h.bestInput/10.0 if h.lastLastVal > h.lastVal and h.currentVal > h.lastVal and h.NotPast180: h.NotPast180 = False if h.NotPast180: h.lastInput, b.Input = b.Input, b.Input + inputInc b.Start(a) else: print "Best input:", h.bestInput print "Last input:", h.lastInput b.Stop() a.AnEvent += AnEventHandler b.Start(a) PHCStruct.py: class Helper(): def __init__(self): self.currentVal = 0 self.lastVal = 0 self.lastLastVal = 0 self.NotPast90 = True self.NotPast180 = True self.bestInput = 0 self.lastInput = 0 PythonHelpClasses has two small classes I wrote in C# before I realised how to do it in Ironpython. Executor runs a delegate asynchronously while it's running member is true. The important code: public void Start(HasAnEvent hae) { running = true; RunDelegate r = new RunDelegate(hae.UpdateNumber); AsyncCallback ac = new AsyncCallback(UpdateDone); IAsyncResult ar = r.BeginInvoke(Input, ac, null); } public void Stop() { running = false; } public void UpdateDone(IAsyncResult ar) { RunDelegate r = (RunDelegate)((AsyncResult)ar).AsyncDelegate; r.EndInvoke(ar); if (running) { AsyncCallback ac = new AsyncCallback(UpdateDone); IAsyncResult ar2 = r.BeginInvoke(Input, ac, null); } } HasAnEvent has a function that generates the sin of its input and fires an event with that result as its argument. i.e.: public void UpdateNumber(double val) { AnEventArgs e = new AnEventArgs(Math.Sin(val)); System.Threading.Thread.Sleep(1000); if (null != AnEvent) { AnEvent(e); } } The sleep is in there just to slow things down a bit. The problem I am getting is that the algorithm is not coming up with the best input being PI/2 and the final input being PI, but I can't see why. Also the best and final inputs are different each time I run the programme. Can anyone see why? Also when the algorithm terminates the best and final inputs are printed to the screen multiple times, not just once. Can someone explain why?

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