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  • RoR routing problem. Calling custom action, but getting redirected to show action

    - by conorgil
    I am working on a project in ruby on rails and I am having a very difficult time with a basic problem. I am trying to call a custom action in one of my controllers, but the request is somehow getting redirected to the default 'show' action and I cannot figure out why. link in edit.html.erb: <%= link_to 'Mass Text Entry', :action=>"create_or_add_food_item_from_text" %> Error from development.log: ActiveRecord::RecordNotFound (Couldn't find Menu with ID=create_or_add_food_item_from_text): app/controllers/menus_controller.rb:20:in `show' routes.rb file: ActionController::Routing::Routes.draw do |map| map.resources :nutrition_objects map.resources :preference_objects map.resources :institutions map.resources :locations map.resources :menus map.resources :food_items map.resources :napkins map.resources :users map.resource :session, :controller => 'session' map.root :controller=>'pages', :action=>'index' map.about '/about', :controller=>'pages', :action=>'about' map.contact '/contact', :controller=>'pages', :action=>'contact' map.home '/home', :controller=>'pages', :action=>'index' map.user_home '/user/home', :controller=>'rater', :action=>'index' map.user_napkins '/user/napkins', :controller=>'rater', :action=>'view_napkins' map.user_preferences '/user/preferences',:controller=>'rater', :action=>'preferences' map.blog '/blog', :controller=>'pages', :action=>'blog' map.signup '/signup', :controller=>'users', :action=>'new' map.login '/login', :controller=>'session', :action=>'new' map.logout '/logout', :controller=>'session', :action=>'destroy' # Install the default routes as the lowest priority. map.connect ':controller/:action' map.connect ':controller/:action/:id' map.connect ':controller/:action/:id.:format' end Menus_controller.rb: class MenusController < ApplicationController ... def create_or_add_food_item_from_text end ... end create_or_add_food_item_from_text.html.erb simply has a div to show a form with a text box in it. I have the rest of my app working fine, but this is stumping me. Any help is appreciated.

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  • A generic error has occurred in GDI+

    - by sysigy
    I know this has been asked a million times but I think I need to make it a million and one. I am getting "A generic error has occurred in GDI+" when trying to save a new bitmap. I have completely stripped down to the most basic lines of code and I still get the error with the following method: public class HomeController : Controller { public ActionResult Index() { return this.View(); } public void CreatePicture() { try { // THIS WORKS System.IO.File.Copy("C:\\copyTest.bmp", "C:\\test folder\\copyTest2.bmp"); // THIS WORKS System.IO.File.Delete("C:\\test folder\\deleteTest.bmp"); using (Bitmap newBitmap = new Bitmap(120, 120)) { // THIS FAILS newBitmap.Save("C:\\test folder\\test.bmp", ImageFormat.Bmp); } } catch (Exception ex) { throw ex; } } } The code is called from an html link on a blank page within an MVC 3.0 website using anonymous login. View: @Html.ActionLink("Create Picture", "CreatePicture", "Home", new { }) I have checked the folder permissions of "test folder" and have given full access to the following: ASPNET NETWORK SERVICE IUSR I still get the error... what have I missed / done wrong ?

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  • Splitting a string which contain multiple symbols to get specific values

    - by Eon Rusted du Plessis
    I cannot believe I am having trouble with this following string String filter = "name=Default;pattern=%%;start=Last;end=Now"; This is a short and possibly duplicate question, but how would I split this string to get: string Name = "Default"; string Pattern = "%%" ; string start = "Last" ; string end = "Now" ; Reason why I ask is my deadline is very soon, and this is literally the last thing I must do. I'm Panicking, and I'm stuck on this basic command. I tried: pattern = filter.Split(new string[] { "pattern=", ";" }, StringSplitOptions.RemoveEmptyEntries)[1]; //Gets the pattern startDate = filter.Split(new string[] { "start=", ";" }, StringSplitOptions.RemoveEmptyEntries)[1]; //Gets the start date I happen to get the pattern which I needed, but as soon as I try to split start, I get the value as "Pattern=%%" What can I do? Forgot to mention The list in this string which needs splitting may not be in any particular order . this is a single sample of a string which will be read out of a stringCollection (reading these filters from Properties.Settings.Filters

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  • Progressive enhancement of anchor tags to avoid onclick="return false;"

    - by Chris Beck
    Unobtrusive JS suggests that we don't have any onclick attributes in our HTML templates. <a href="/controller/foo/1">View Foo 1</a> A most basic progressive enhancement is to convert an that anchor tag to use XHR to retrieve a DOM fragment. So, I write JS to add an event listener for a."click" then make an XHR to a.href. Alas, the browser still wants to navigate to "/controller/foo". So, I write JS to dynamically inject a.onclick = "return false;". Still unobtrusive (I guess), but now I'm paying the the cost of an extra event handler. To avoid the cost of 2 event listeners, I could shove my function call into the onclick attribute <a href="/controller/foo/1" onclick="myXHRFcn(); return false;"> But that's grodo for all sorts of reasons. To make it more interesting, I might have 100 anchor tags that I want to enhance. A better pattern is a single listener on a parent node that relies on event bubbling. That's cool, but how do I short circuit the browser from navigating to the URL without this on every anchor node? onclick="return false;" Manipulating the href is not an option. It must stay intact so the context menu options to copy or open in new page work as expected.

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  • Listening UDP or switch to TCP in a MFC application

    - by Alexander.S
    I'm editing a legacy MFC application, and I have to add some basic network functionalities. The operating side has to receive a simple instruction (numbers 1,2,3,4...) and do something based on that. The clients wants the latency to be as fast as possible, so naturally I decided to use datagrams (UDP). But reading all sorts of resources left me bugged. I cannot listen to UDP sockets (CAsyncSocket) in MFC, it's only possible to call Receive which blocks and waits. Blocking the UI isn't really a smart. So I guess I could use some threading technique, but since I'm not all that experienced with MFC how should that be implemented? The other part of the question is should I do this, or revert to TCP, considering reliability and implementation issues. I know that UDP is unreliable, but just how unreliable is it really? I read that it is up to 50% faster, which is a lot for me. References I used: http://msdn.microsoft.com/en-us/library/09dd1ycd(v=vs.80).aspx

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  • LINQ to SQL - Lightweight O/RM?

    - by CoffeeAddict
    I've heard from some that LINQ to SQL is good for lightweight apps. But then I see LINQ to SQL being used for Stackoverflow, and a bunch of other .coms I know (from interviewing with them). Ok, so is this true? for an e-commerce site that's bringing in millions and you're typically only doing basic CRUDs most the time with the exception of an occasional stored proc for something more complex, is LINQ to SQL complete enough and performance-wise good enough or able to be tweaked enough to run happily on an e-commerce site? I've heard that you just need to tweak performance on the DB side when using LINQ to SQL for a better approach. So there are really 2 questions here: 1) Meaning/scope/definition of a "Lightweight" O/RM solution: What the heck does "lightweight" mean when people say LINQ to SQL is a "lightweight O/RM" and is that true??? If this is so lightweight then why do I see a bunch of huge .coms using it? Is it good enough to run major .coms (obviously it looks like it is) and what determines what the context of "lightweight" is...it's such a generic statement. 2) Performance: I'm working on my own .com and researching different O/RMs. I'm not really looking at the Entity Framework (yet), just want to figure out the LINQ to SQL basics here and determine if it will be efficient enough for me. The problem I think is you can't tweak or control the SQL it generates...

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  • lapply slower than for-loop when used for a BiomaRt query. Is that expected?

    - by ptocquin
    I would like to query a database using BiomaRt package. I have loci and want to retrieve some related information, let say description. I first try to use lapply but was surprise by the time needed for the task to be performed. I thus tried a more basic for-loop and get a faster result. Is that expected or is something wrong with my code or with my understanding of apply ? I read other posts dealing with *apply vs for-loop performance (Here, for example) and I was aware that improved performance should not be expected but I don't understand why performance here is actually lower. Here is a reproducible example. 1) Loading the library and selecting the database : library("biomaRt") athaliana <- useMart("plants_mart_14") athaliana <- useDataset("athaliana_eg_gene",mart=athaliana) 2) Querying the database : loci <- c("at1g01300", "at1g01800", "at1g01900", "at1g02335", "at1g02790", "at1g03220", "at1g03230", "at1g04040", "at1g04110", "at1g05240" ) I create a function for the use in lapply : foo <- function(loci) { getBM("description","tair_locus",loci,athaliana) } When I use this function on the first element : > system.time(foo(cwp_loci[1])) utilisateur système écoulé 0.020 0.004 1.599 When I use lapply to retrieve the data for all values : > system.time(lapply(loci, foo)) utilisateur système écoulé 0.220 0.000 16.376 I then created a new function, adding a for-loop : foo2 <- function(loci) { for (i in loci) { getBM("description","tair_locus",loci[i],athaliana) } } Here is the result : > system.time(foo2(loci)) utilisateur système écoulé 0.204 0.004 10.919 Of course, this will be applied to a big list of loci, so the best performing option is needed. I thank you for assistance. EDIT Following recommendation of @MartinMorgan Simply passing the vector loci to getBM greatly improves the query efficiency. Simpler is better. > system.time(lapply(loci, foo)) utilisateur système écoulé 0.236 0.024 110.512 > system.time(foo2(loci)) utilisateur système écoulé 0.208 0.040 116.099 > system.time(foo(loci)) utilisateur système écoulé 0.028 0.000 6.193

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  • How to have table span the entire height?

    - by Yogendra
    Hi All, I have a html table and I am trying to have it span the entire page height. For some reason I am not able to get this to work. I have set the html, body and table height to be 100%, but the table still does not occupy the entire 100%. Heres the code. It is very basic because I am just trying to have the table occupy the entire height. <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApplication1.WebForm1" %> <style type="text/css"> body,html { margin:0; padding:0; height:100%; } </style> <table border="2" cellpadding="0" cellspacing="0" style="height:100%; width:100%" > <tr> <td>ABCD</td> </tr> </table> </form> I tried for couple of hours and I could not get it to work. Any help is really appreciated.

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  • Data confusion - Selecting data in one DataGridView based on selection in another

    - by Logan Young
    This probably isn't the best way to do what I want, but I can't think of anything else to try... NB: I'm using Visual Basic.NET My form has 2 DataGridView controls. One of these is bound to a DataSet, the other isn't visible - at least not until the user selects a uniqueidentifier cell in the 1st grid. When the user makes this selection, the 2nd grid will become visible and display the row from another with the same id as the one selected in the 1st grid. So, basically, I want to dynamically display data in one grid based on user selection in another grid. My code looks like this so far... Private Sub RulesGrid_CellClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles RulesGrid.CellClick Try FlagsGrid.Visible = True ''// MsgBox(RulesGrid.CurrentCell.Value.ToString()) Dim sql As String = "SELECT * FROM ctblMKA_Status_Flags " + _ "WHERE intStatusID = '" & RulesGrid.CurrentCell.Value & "'" DSFlags = GetDS(sql) DSFlags.DataSetName = "FlagsDataSet" FlagsGrid.DataSource = DSFlags ProgressBar.Visible = False Catch ex As Exception MsgBox(ex.ToString) End Try End Sub I feel like I'm missing something here... Any ideas anyone?

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  • Visual C++ function suddenly 170 ms slower (4x longer)

    - by Mikael
    For the past few months I've been working on a Visual C++ project to take images from cameras and process them. Up until today this has taken about 65 ms to update the data but now it has suddenly increased significantly. What happens is: I launch my program and for the first 30 or so iterations it performs as expected, then suddenly the loop time increases from 65 ms to 250 ms. The odd thing is, after timing each function I found out that the part of the code which is causing the slowdown is fairly basic and has not been modified in over a month. The data which goes into it is unchanged and identical every iteration but the execution time which is initially less than 1 ms suddenly increases to 170 ms while the rest of the code is still performing as expected (time-wise). Basically, I am calling the same function over and over, for the first 30 calls it performs as it should, after that it slows down for no apparent reason. It might also be worth noting that it is a sudden change in execution time, not a gradual increase. What could be causing this? The code is leaking some memory (~50 kb/s) but not nearly enough to warrant a sudden 4x slowdown. If anyone has any ideas I'd love to hear them!

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  • Rails: creating a model in the new action

    - by Joseph Silvashy
    I have an interesting situation, well it's probably not that unique at all, but I'm not totally sure how to tackle it. I have a model, in this case a recipe and the user navigates to the new path /recipes/new however the situation is that I need to be able to have the user upload images and make associations to that model in the new action, but the model doesn't have an ID yet. So I assume I need to rethink my controller, but I don't want to have redirects and whatnot, how can accomplish this? Here is the basic controller, barebones obviously: ... def new # I should be creating the model first, so it has an ID @recipe = Recipe.new end def create @recipe = Recipe.new(params[:recipe]) if @recipe.save redirect_to @recipe else render 'new' end end ... update Perhaps I can have a column thats like state which could have values like new/incomplete/complete or what-have-you. I'm mostly trying to figure out what would also be most efficient for the DB. It would be nice if I could still have a url that said '/new', instead of it be the edit path with the id, for usability sake, but I'm not sure this can be simply accomplished in the new action of my controller. Thoughts?

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  • Centered DIV w/ width dependant on text, buffered by two divs that should fill the containing DIV

    - by Andrew Thompson
    I have been wracking my brains on this seemingly small issue the whole day. My web dev friends are baffled and I could not find a suitable answer in my search of this site and others (though, I could have missed it somewhere along the way). Here's the problem: 3 DIVS within one fixed-width container DIV The center DIV has text that will be different on other sites The center DIV needs to be centered, and no larger than the text it contains. This is what I'd like to end up with The basic HTMl: <div id="container" > <div id="left" ></div> <div id="center" >Text inside center should resize this block</div> <div id="right" ></div> </div> Below, I removed most of the styles I have tried. This CSS currently centers the DIV (if I set it as an inline block), but I need the other divs to fill the left and right space remaining: #container { width:750px; text-align:center; } #left { background-color:#E85355; } #center { background-color:#CDD7D7; display:inline-block; } #right { background-color:#65A8A6; } I've tried floating, no-wrap, overflow, etc. Thanks a million to whomever can offer some help! JSFiddle Link

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  • Java : Inner class of an interface (from google guice)

    - by bsreekanth
    Hello, I was going through the source of google guice, and found an unfamiliar piece of code. It would be great learning if someone can clarify it. I have very basic understanding of inner classes, as they keep the implementation details close to the public interface. Otherwise the inner class may pollute the namespace. Now, I see the below lines at public static final Scope SINGLETON = new Scope() { public <T> Provider<T> scope(final Key<T> key, final Provider<T> creator) { return new Provider<T>() { ......... } It assign an inner class instance to the static variable, but Scope is an interface defined as (at) public interface Scope Is it possible to instantiate the interface?? or is it a succinct syntax for an anonymous implementation of an interface?? If anyone can explain what the author is intended by multiple nested classes above (Scope and Provider), and why it make sense to implement this way, it would help me to understand. thanks.

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  • c# How to find if two objects are equal

    - by Simon G
    Hi, I'm needing to know the best way to compare two objects and to find out if there equal. I'm overriding both GethashCode and Equals. So a basic class looks like: public class Test { public int Value { get; set; } public string String1 { get; set; } public string String2 { get; set; } public override int GetHashCode() { return Value ^ String1.GetHashCode() ^ String2.GetHashCode(); } public override bool Equals( object obj ) { return GetHashCode() == obj.GetHashCode(); } } So for testing purposes I created two objects: Test t = new Test() { Value = 1, String1 ="One", String2 = "One" }; Test t2 = new Test() { Value = 1, String1 = "Two", String2 = "Two" }; bool areEqual = t.Equals( t2 ); In testing this areEqual returns true event though both objects are different. I realise this is because String1 and String2 are the same value in each object and thus cancels each other out when hashing. Is there a better way off hashing object that the method I have that will resolve my issue?

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  • I want to build a Google-friendly web app, where should I start?

    - by ronii
    I have only very basic experience with HTML/CSS and have quite a bit of experience with testing software and web apps from a consumer perspective. I'd love to launch a web application that plays nicely with Google services, similar to some of the apps you'd find on the Google Apps Marketplace, such as ManyMoon, time to note, Socialwok, etc. I'm a huge Google fan and would like to build something that's well integrated with other Google services. If you were a total beginner and wanted to build a complex app like one of examples above (project management, CRM, etc), where would you start? If you worked your ass off 18 hours a day, 24/7, how fast could you do it? I've dabbled into various languages and development frameworks, and read about which apps are using what languages but it's hard to figure out what would be most beneficial to jump into. Ruby on Rails, PHP, Google Web Toolkit, AppEngine. The list goes on and on. I want to be able to build and launch my own scalable web app. Thanks.

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  • How to query multiple tables with multiple selects MySQL

    - by brybam
    I'm trying to write a php function that gets all the basic food data(this part works fine in my code) Then grabs all the ingredients related to the ids of the selected items from the query before. Anyone have have any idea why my second array keeps coming back as false? I should be getting 1 array with the list of foods (this works) Then, the second one should be an array with all the ingredients for all the foods that were previously selected...then in my code im planning to work with the array and sort them with the proper foods based on the ids. function getFood($start, $limit) { $one = mysql_query("SELECT a.id, a.name, a.type, AVG(b.r) AS fra, COUNT(b.id) as tvotes FROM `foods` a LEFT JOIN `foods_ratings` b ON a.id = b.id GROUP BY a.id ORDER BY fra DESC, tvotes DESC LIMIT $start, $limit;"); $row = mysql_fetch_array($one); $qry = ""; foreach ($row as &$value) { $fid = $value['id']; $qry = $qry . "SELECT ing, amount FROM foods_ing WHERE fid='$fid';"; } $two = mysql_query($qry); return array ($one, $two); }

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  • Help me sort programing languages a bit

    - by b-gen-jack-o-neill
    Hi, so I asked here few days ago about C# and its principles. Now, if I may, I have some additional general questions about some languages, becouse for novice like me, it seems a bit confusing. To be exact I want to ask more about language functions capabilities than syntax and so. To be honest, its just these special functions that bothers me and make me so confused. For exmaple, C has its printf(), Pascal has writeln() and so. I know in basic the output in assembler of these funtions would be similiar, every language has more or less its special functions. For console output, for file manipulation, etc. But all these functions are de-facto part of its OS API, so why is for example in C distinguished between C standard library functions and (on Windows) WinAPI functions when even printf() has to use some Windows feature, call some of its function to actually show desired text on console window, becouse the actuall "showing" is done by OS. Where is the line between language functions and system API? Now languages I dont quite understand - Python, Ruby and similiar. To be more specific, I know they are similiar to java and C# in term they are compiled into bytecode. But, I do not unerstand what are its capabilities in term of building GUI applications. I saw tutorial for using Ruby to program GUI applications on Linux and Windows. But isn´t that just some kind of upgrade? I mean fram other tutorials It seemed like these languages was first intended for small scripts than building big applications. I hope you understand why I am confused. If you do, please help me sort it out a bit, I have no one to ask.

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  • Spring Data Neo4J @Indexed(unique = true) not working

    - by Markus Lamm
    I'm new to Neo4J and I have, probably an easy question. There're NodeEntitys in my application, a property (name) is annotated with @Indexed(unique = true) to achieve the uniqueness like I do in JPA with @Column(unique = true). My problem is, that when I persist an entity with a name that already exists in my graph, it works fine anyway. But I expected some kind of exception here...?! Here' s an overview over basic my code: @NodeEntity public abstract class BaseEntity implements Identifiable { @GraphId private Long entityId; ... } public class Role extends BaseEntity { @Indexed(unique = true) private String name; ... } public interface RoleRepository extends GraphRepository<Role> { Role findByName(String name); } @Service public class RoleServiceImpl extends BaseEntityServiceImpl<Role> implements { private RoleRepository repository; @Override @Transactional public T save(final T entity) { return getRepository().save(entity); } } And this is my test: @Test public void testNameUniqueIndex() { final List<Role> roles = Lists.newLinkedList(service.findAll()); final String existingName = roles.get(0).getName(); Role newRole = new Role.Builder(existingName).build(); newRole = service.save(newRole); } That's the point where I expect something to go wrong! How can I ensure the uniqueness of a property, without checking it for myself?? THANKS IN ADVANCE FOR ANY IDEAS!! P.S.: I'm using neo4j 1.8.M07, spring-data-neo4j 2.1.0.BUILD-SNAPSHOT and Spring 3.1.2.RELEASE.

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  • Using map() on a _set in a template?

    - by Stuart Grimshaw
    I have two models like this: class KPI(models.Model): """KPI model to hold the basic info on a Key Performance Indicator""" title = models.CharField(blank=False, max_length=100) description = models.TextField(blank=True) target = models.FloatField(blank=False, null=False) group = models.ForeignKey(KpiGroup) subGroup = models.ForeignKey(KpiSubGroup, null=True) unit = models.TextField(blank=True) owner = models.ForeignKey(User) bt_measure = models.BooleanField(default=False) class KpiHistory(models.Model): """A historical log of previous KPI values.""" kpi = models.ForeignKey(KPI) measure = models.FloatField(blank=False, null=False) kpi_date = models.DateField() and I'm using RGraph to display the stats on internal wallboards, the handy thing is Python lists get output in a format that Javascript sees as an array, so by mapping all the values into a list like this: def f(x): return float(x.measure) stats = map(f, KpiHistory.objects.filter(kpi=1) then in the template I can simply use {{ stats }} and the RGraph code sees it as an array which is exactly what I want. [87.0, 87.5, 88.5, 90] So my question is this, is there any way I can achieve the same effect using Django's _set functionality to keep the amount of data I'm passing into the template, up until now I've been passing in a single KPI object to be graphed but now I want to pass in a whole bunch so is there anything I can do with _set {{ kpi.kpihistory_set }} dumps the whole model out, but I just want the measure field. I can't see any of the built in template methods that will let me pull out just the single field I want. How have other people handled this situation?

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  • Returning objects in php

    - by user220201
    I see similar questions asked but I seem to have problem with more basic stuff than were asked. How to declare a variable in php? My specific problem is I have a function that reads a DB table and returns the record (only one) as an object. class User{ public $uid; public $name; public $status; } function GetUserInfo($uid) { // Query DB $userObj = new User(); // convert the result into the User object. var_dump($userObj); return $userObj; } // In another file I call the above function. .... $newuser = GetUserInfo($uid); var_dump($newuser); What is the problem here, I cannot understand. Essentially the var_dump() in the function GetUserInfo() works fine. The var_dump() outside after the call to GetUserInfo() does not work. Thanks for any help. S

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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 debug JBoss out of memory problem?

    - by user561733
    Hello, I am trying to debug a JBoss out of memory problem. When JBoss starts up and runs for a while, it seems to use memory as intended by the startup configuration. However, it seems that when some unknown user action is taken (or the log file grows to a certain size) using the sole web application JBoss is serving up, memory increases dramatically and JBoss freezes. When JBoss freezes, it is difficult to kill the process or do anything because of low memory. When the process is finally killed via a -9 argument and the server is restarted, the log file is very small and only contains outputs from the startup of the newly started process and not any information on why the memory increased so much. This is why it is so hard to debug: server.log does not have information from the killed process. The log is set to grow to 2 GB and the log file for the new process is only about 300 Kb though it grows properly during normal memory circumstances. This is information on the JBoss configuration: JBoss (MX MicroKernel) 4.0.3 JDK 1.6.0 update 22 PermSize=512m MaxPermSize=512m Xms=1024m Xmx=6144m This is basic info on the system: Operating system: CentOS Linux 5.5 Kernel and CPU: Linux 2.6.18-194.26.1.el5 on x86_64 Processor information: Intel(R) Xeon(R) CPU E5420 @ 2.50GHz, 8 cores This is good example information on the system during normal pre-freeze conditions a few minutes after the jboss service startup: Running processes: 183 CPU load averages: 0.16 (1 min) 0.06 (5 mins) 0.09 (15 mins) CPU usage: 0% user, 0% kernel, 1% IO, 99% idle Real memory: 17.38 GB total, 2.46 GB used Virtual memory: 19.59 GB total, 0 bytes used Local disk space: 113.37 GB total, 11.89 GB used When JBoss freezes, system information looks like this: Running processes: 225 CPU load averages: 4.66 (1 min) 1.84 (5 mins) 0.93 (15 mins) CPU usage: 0% user, 12% kernel, 73% IO, 15% idle Real memory: 17.38 GB total, 17.18 GB used Virtual memory: 19.59 GB total, 706.29 MB used Local disk space: 113.37 GB total, 11.89 GB used

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  • C++ and its type system: How to deal with data with multiple types?

    - by sub
    "Introduction" I'm relatively new to C++. I went through all the basic stuff and managed to build 2-3 simple interpreters for my programming languages. The first thing that gave and still gives me a headache: Implementing the type system of my language in C++ Think of that: Ruby, Python, PHP and Co. have a lot of built-in types which obviously are implemented in C. So what I first tried was to make it possible to give a value in my language three possible types: Int, String and Nil. I came up with this: enum ValueType { Int, String, Nil }; class Value { public: ValueType type; int intVal; string stringVal; }; Yeah, wow, I know. It was extremely slow to pass this class around as the string allocator had to be called all the time. Next time I've tried something similar to this: enum ValueType { Int, String, Nil }; extern string stringTable[255]; class Value { public: ValueType type; int index; }; I would store all strings in stringTable and write their position to index. If the type of Value was Int, I just stored the integer in index, it wouldn't make sense at all using an int index to access another int, or? Anyways, the above gave me a headache too. After some time, accessing the string from the table here, referencing it there and copying it over there grew over my head - I lost control. I had to put the interpreter draft down. Now: Okay, so C and C++ are statically typed. How do the main implementations of the languages mentioned above handle the different types in their programs (fixnums, bignums, nums, strings, arrays, resources,...)? What should I do to get maximum speed with many different available types? How do the solutions compare to my simplified versions above?

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  • Emulating a computer running MS-DOS

    - by Richard
    Writing emulators has always fascinated me. Now I want to write an emulator for an IBM PC and run MS-DOS on it (I've got the floppy image files). I have good experience in C++ and C and basic knowledge of assembler and the architecture of a CPU. I also know that there are thousands of emulators out there doing exactly what I want to do, but I'd be doing this for pure joy only. How much work do I have to expect? (If my goal is to boot DOS and create a text file with it, all emulated) What CPU should I emulate ? Where can I find documentation on how the machine code is organized and which opcodes mean what, so I can unpack and execute them correctly with my emulator? Does MS-DOS still run on the newest generations of processors? Would it theoretically be able to natively run on a 64-bit AMD Phenom 2 processor w/ a modern mainboard, HDD, RAM, etc.? What else, besides emulating the CPU, could be an important factor (in terms of difficulty)? I would only aim for outputting / inputting text to the system via the host system's console, no sound or other more advanced IO etc. Have you written an emulator yet? What was your first one for? How hard was it? Do you have any special tips for me? Thanks in advance

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  • How do software events work internally?

    - by Duddle
    Hello! I am a student of Computer Science and have learned many of the basic concepts of what is going on "under the hood" while a computer program is running. But recently I realized that I do not understand how software events work efficiently. In hardware, this is easy: instead of the processor "busy waiting" to see if something happened, the component sends an interrupt request. But how does this work in, for example, a mouse-over event? My guess is as follows: if the mouse sends a signal ("moved"), the operating system calculates its new position p, then checks what program is being drawn on the screen, tells that program position p, then the program itself checks what object is at p, checks if any event handlers are associated with said object and finally fires them. That sounds terribly inefficient to me, since a tiny mouse movement equates to a lot of cpu context switches (which I learned are relatively expensive). And then there are dozens of background applications that may want to do stuff of their own as well. Where is my intuition failing me? I realize that even "slow" 500MHz processors do 500 million operations per second, but still it seems too much work for such a simple event. Thanks in advance!

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