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  • Can someone tell me why I'm seg faulting in this simple C program?

    - by user299648
    I keep on getting seg faulted, and for the life of me I dont why. The file I'm scanning is just 18 strings in 18 lines. I thinks the problem is the way I'm mallocing the double pointer called picks, but I dont know exactly why. I'm am only trying to scanf strings that are less than 15 chars long, so I don't see the problem. Can someone please help. #include <stdio.h> #include <stdlib.h> #include <string.h> #define MAX_LENGTH 100 int main( int argc,char *argv[] ) { char* string = malloc( sizeof(char) ); char** picks = malloc(15*sizeof(char)); FILE* pick_file = fopen( argv[l], "r" ); int num_picks; for( num_picks=0 ; fgets( string, MAX_LENGTH, pick_file ) != NULL ; num_picks++ ) { printf("pick a/an %s ", string ); scanf( "%s", picks+num_picks ); } int x; for(x=0; x<num_picks;x++) printf("s\n", picks+x); }

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  • How can I merge two lists and sort them working in 'linear' time?

    - by Sergio Tapia
    I have this, and it works: # E. Given two lists sorted in increasing order, create and return a merged # list of all the elements in sorted order. You may modify the passed in lists. # Ideally, the solution should work in "linear" time, making a single # pass of both lists. def linear_merge(list1, list2): finalList = [] for item in list1: finalList.append(item) for item in list2: finalList.append(item) finalList.sort() return finalList # +++your code here+++ return But, I'd really like to learn this stuff well. :) What does 'linear' time mean?

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  • When I run cxxtest I get this error that I dont underdstand?

    - by user299648
    ./cxxtest/cxxtestgen.py -o tests.cpp --error-printer DrawTestSuite.h g++ -I./cxxtest/ -c tests.cpp g++ -o tests tests.o Color.o tests.o: In function DrawTestSuite::testLinewidthOne()': tests.cpp:(.text._ZN13DrawTestSuite16t… undefined reference toLinewidth::Linewidth(double)' tests.cpp:(.text._ZN13DrawTestSuite16t… undefined reference to `Linewidth::draw(std::basic_ostream &)' collect2: ld returned 1 exit status make: * [tests] Error 1// DrawTestSuite.h DrawTestSuite.h contains the unit-test and The test function calls on Linewidth.h to execute the constructer and member function draw I have include "Linewidth.h" in DrawTestSuite.h

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  • Can some tell me why I am seg faulting in this simple C program?

    - by user299648
    I keep on getting seg faulted after I end my first for loop, and for the life of me I don't why. The file I'm scanning is just 18 strings in 18 lines. I thinks the problem is the way I'm mallocing the double pointer called picks, but I don't know exactly why. I'm am only trying to scanf strings that are less than 15 chars long, so I don't see the problem. Can someone please help. #include <stdio.h> #include <stdlib.h> #include <string.h> #define MAX_LENGTH 100 int main( int argc,char *argv[] ) { char* string = malloc( 15*sizeof(char) ); char** picks = malloc(15*sizeof(char*)); FILE* pick_file = fopen( argv[l], "r" ); int num_picks; for( num_picks=0 ; fgets( string, MAX_LENGTH, pick_file ) != NULL ; num_picks++ ) { scanf( "%s", picks+num_picks ); } //this is where i seg fault int x; for(x=0; x<num_picks;x++) printf("s\n", picks+x); }

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  • iPhone Apps, Objective C, a Graph, and Functions vs. Objects (or something like that)

    - by BillEccles
    Gentleones, I've got a UIImageView that I have in a UIView. This particular UIImageView displays a PNG of a graph. It's important for this particular view controller and another view controller to know what the graph "looks like," i.e., the function described by the PNG graph. These other view controllers need to be able to call a "function" of some sort with the X value returning the Y value. Please ignore the fact (from an outsider's perspective) that I could probably generate the graph programmatically. So my questions are: 1 - Where should I put this function? Should it go in one view controller or the other, or should it go in its own class or main or...? 2 - Should it be an object in some way? Or should it be a straight function? (In either case, where's it belong?) Pardon the apparent n00b-iness of the question. It's 'cause I'm honestly a n00b! This OOP stuff is giving my head a spin having been a procedural programmer for 30 years. (And I choose to learn it by jumping into an iPhone app. Talk about baptism by fire!) Thanks in advance,Bill

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  • How to add a writable folder to the PHP document root on linux

    - by Ron Whites
    We are building an example bash script for our PHP TestCoverage Tool use on Linux. The development environment is Ubuntu 12.04_1 but we intend to have the linux example work across as many linux versions as possible without modification. The example linux script requires a variable be set to the PHP Document Root path and by default uses a small PHP example source to show the user how our GUI and text report shows the covered and uncovered PHP code areas. The linux script is also intended to be easily alterable by the user to automate the TestCoverage display of users PHP code. The problem we are having with Ubuntu 12.04 (any linux?) is that the PHP Apache2 document root is defined in /etc/apache2/sites-available/default as /var/www and /var/www is defaulted with "drwxr-xr-x" read only access. So in order to add our own folder as /var/www/SDTestCoverage we must change /var/www to "drwxrwxrwx" read-write access. So it seems our script (at least on Ubuntu) will need to ... 1. acquire and save the /var/www permissions then do .. 2. sudo chmod 777 /var/www (to make writable) 3. mkdir -p /var/www/SDTestCoverage (create our folder under the document root) 4. sudo chmod 777 /var/www/SDTestCoverage (make our subfolder writable) 5. and finally restore /var/www permissions Thanks and our Questions are .. 1. Is this the standard way (using Ubuntu) one adds a writable folder under the PHP Document Root? 2. Is this the most general purpose way one adds a writable folder under the PHP Document Root on other versions of Linux?

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  • Cocoa : How do I catch drag operations initiated from an IKBrowserView?

    - by bucketmouse
    So I've got an IKBrowserView all wired up and happily dragging my custom datatype (provided lazily via PasteboardItem) from one window to another, but now I'm interested in detecting when the user drops some data onto the trashcan. Cocoa's documentation says to check the return type of the drag operation itself, but how exactly do I do this with an IKBrowserView? Once I call imageBrowser:writeItemsAtIndexes:toPasteboard: I don't seem to get any notifications other than the request for the pasteboard contents, which doesn't provide a pointer to the drag operation that invoked it.

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  • Java library suggestions for implementing a custom web server

    - by dexter
    I would like to create a web server that will serve/accept json files through REST. The JSON files being served will come from a database query and format the results into JSON. Any suggestions for a good java library. I have tried using Apache HTTPComponents. While maybe I can just create a servlet but I am not really allowed to install a servlet container in the server machine.

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  • Returning currently displayed index of an array Javascript...

    - by Jeff Kindred
    I have a simple array with x number of items. I am displaying them individually via a link click... I want to update a number that say 1 of 10. when the next one is displayed i want it to display 2 of 10 etc... I have looked all around and my brain is fried right now... I know its simple I just cant get it out. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title>Page Title</title> <link rel="stylesheet" href="style.css" type="text/css" media="screen" charset="utf-8"/> <script type="text/javascript"> var quotations = new Array() quotations[0]= "1" quotations[1]= "2" quotations[2]= "3" quotations[3]= "4" quotations[4]= "5" quotations[5]= "6" quotations[6]= "7" numQuotes = quotations.length; curQuote = 1; function move( xflip ) { curQuote = curQuote + xflip; if (curQuote > numQuotes) { curQuote = 1 ; } if (curQuote == 0) { curQuote = numQuotes ; } document.getElementById('quotation').innerHTML=quotations[curQuote - 1]; } var curPage = //this is where the current index should go </script> </head> <body> <div id="quotation"> <script type="text/javascript">document.write(quotations[0]);</script> </div> <div> <p><a href="javascript();" onclick="move(-1)">GO back</a> <script type="text/javascript">document.write(curPage + " of " + numQuotes)</script> <a href="javascript();" onclick="move(1)">GO FORTH</a></p> </div> </body> </html>

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  • is there a better way to write this frankenstein LINQ query that searches for values in a child tabl

    - by MRV
    I have a table of Users and a one to many UserSkills table. I need to be able to search for users based on skills. This query takes a list of desired skills and searches for users who have those skills. I want to sort the users based on the number of desired skills they posses. So if a users only has 1 of 3 desired skills he will be further down the list than the user who has 3 of 3 desired skills. I start with my comma separated list of skill IDs that are being searched for: List<short> searchedSkillsRaw = skills.Value.Split(',').Select(i => short.Parse(i)).ToList(); I then filter out only the types of users that are searchable: List<User> users = (from u in db.Users where u.Verified == true && u.Level > 0 && u.Type == 1 && (u.UserDetail.City == city.SelectedValue || u.UserDetail.City == null) select u).ToList(); and then comes the crazy part: var fUsers = from u in users select new { u.Id, u.FirstName, u.LastName, u.UserName, UserPhone = u.UserDetail.Phone, UserSkills = (from uskills in u.UserSkills join skillsJoin in configSkills on uskills.SkillId equals skillsJoin.ValueIdInt into tempSkills from skillsJoin in tempSkills.DefaultIfEmpty() where uskills.UserId == u.Id select new { SkillId = uskills.SkillId, SkillName = skillsJoin.Name, SkillNameFound = searchedSkillsRaw.Contains(uskills.SkillId) }), UserSkillsFound = (from uskills in u.UserSkills where uskills.UserId == u.Id && searchedSkillsRaw.Contains(uskills.SkillId) select uskills.UserId).Count() } into userResults where userResults.UserSkillsFound > 0 orderby userResults.UserSkillsFound descending select userResults; and this works! But it seems super bloated and inefficient to me. Especially the secondary part that counts the number of skills found. Thanks for any advice you can give. --r

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  • How strict should I be in the "do the simplest thing that could possible work" while doing TDD

    - by Support - multilanguage SO
    For TDD you have to Create a test that fail Do the simplest thing that could possible work to pass the test Add more variants of the test and repeat Refactor when a pattern emerge With this approach you're supposing to cover all the cases ( that comes to my mind at least) but I'm wonder if am I being too strict here and if it is possible to "think ahead" some scenarios instead of simple discover them. For instance, I'm processing a file and if it doesn't conform to a certain format I am to throw an InvalidFormatException So my first test was: @Test void testFormat(){ // empty doesn't do anything... processor.validate("empty.txt"); try { processor.validate("invalid.txt"); assert false: "Should have thrown InvalidFormatException"; } catch( InvalidFormatException ife ) { assert "Invalid format".equals( ife.getMessage() ); } } I run it and it fails because it doesn't throw an exception. So the next thing that comes to my mind is: "Do the simplest thing that could possible work", so I : public void validate( String fileName ) throws InvalidFormatException { if(fileName.equals("invalid.txt") { throw new InvalidFormatException("Invalid format"); } } Doh!! ( although the real code is a bit more complicated, I found my self doing something like this several times ) I know that I have to eventually add another file name and other test that would make this approach impractical and that would force me to refactor to something that makes sense ( which if I understood correctly is the point of TDD, to discover the patterns the usage unveils ) but: Q: am I taking too literal the "Do the simplest thing..." stuff?

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  • So, I guess I can't use "&&" in the Python if conditional. Any help?

    - by Sergio Tapia
    Here's my code: # F. front_back # Consider dividing a string into two halves. # If the length is even, the front and back halves are the same length. # If the length is odd, we'll say that the extra char goes in the front half. # e.g. 'abcde', the front half is 'abc', the back half 'de'. # Given 2 strings, a and b, return a string of the form # a-front + b-front + a-back + b-back def front_back(a, b): # +++your code here+++ if len(a) % 2 == 0 && len(b) % 2 == 0: return a[:(len(a)/2)] + b[:(len(b)/2)] + a[(len(a)/2):] + b[(len(b)/2):] else: #todo! Not yet done. :P return I'm getting an error in the IF conditional. What am I doing wrong?

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  • Simplest LINQ in C# troubleshooting.

    - by Jay
    I'm trying to learn a bit of LINQ but I'm having compile issues right off the bat. Is there any specific reason why this won't work? using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace HelloLINQ { class HelloLINQ { public static void Main() { Example1(); } public static void Example1() { var numbers = new int[] { 1, 5, 3, 7, 3, 8, 9, 3, 6, 6, 2 }; var under5 = from n in numbers select n; foreach (var n in under5) { Console.WriteLine(n); } } } } The error is: Could not find an implementation of the query pattern for source type 'int[]'. 'Select' not found. Are you missing a reference to 'System.Core.dll' or a using directive for 'System.Linq'?

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  • Where are possible locations of queueing/buffering delays in Linux multicast?

    - by Matt
    We make heavy use of multicasting messaging across many Linux servers on a LAN. We are seeing a lot of delays. We basically send an enormous number of small packages. We are more concerned with latency than throughput. The machines are all modern, multi-core (at least four, generally eight, 16 if you count hyperthreading) machines, always with a load of 2.0 or less, usually with a load less than 1.0. The networking hardware is also under 50% capacity. The delays we see look like queueing delays: the packets will quickly start increasing in latency, until it looks like they jam up, then return back to normal. The messaging structure is basically this: in the "sending thread", pull messages from a queue, add a timestamp (using gettimeofday()), then call send(). The receiving program receives the message, timestamps the receive time, and pushes it in a queue. In a separate thread, the queue is processed, analyzing the difference between sending and receiving timestamps. (Note that our internal queues are not part of the problem, since the timestamps are added outside of our internal queuing.) We don't really know where to start looking for an answer to this problem. We're not familiar with Linux internals. Our suspicion is that the kernel is queuing or buffering the packets, either on the send side or the receive side (or both). But we don't know how to track this down and trace it. For what it's worth, we're using CentOS 4.x (RHEL kernel 2.6.9).

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  • Why is a non-blocking TCP connect() occasionally so slow on Linux?

    - by pts
    I was trying to measure the speed of a TCP server I'm writing, and I've noticed that there might be a fundamental problem of measuring the speed of the connect() calls: if I connect in a non-blocking way, connect() operations become very slow after a few seconds. Here is the example code in Python: #! /usr/bin/python2.4 import errno import os import select import socket import sys def NonBlockingConnect(sock, addr): while True: try: return sock.connect(addr) except socket.error, e: if e.args[0] not in (errno.EINPROGRESS, errno.EALREADY): raise os.write(2, '^') if not select.select((), (sock,), (), 0.5)[1]: os.write(2, 'P') def InfiniteClient(addr): while True: sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) sock.setblocking(0) sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) # sock.connect(addr) NonBlockingConnect(sock, addr) sock.close() os.write(2, '.') def InfiniteServer(server_socket): while True: sock, addr = server_socket.accept() sock.close() server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) server_socket.bind(('127.0.0.1', 45454)) server_socket.listen(128) if os.fork(): # Parent. InfiniteServer(server_socket) else: addr = server_socket.getsockname() server_socket.close() InfiniteClient(addr) With NonBlockingConnect, most connect() operations are fast, but in every few seconds there happens to be one connect() operation which takes at least 2 seconds (as indicated by 5 consecutive P letters on the output). By using sock.connect instead of NonBlockingConnect all connect operations seem to be fast. How is it possible to get rid of these slow connect()s? I'm running Ubuntu Karmic desktop with the standard PAE kernel: Linux narancs 2.6.31-20-generic-pae #57-Ubuntu SMP Mon Feb 8 10:23:59 UTC 2010 i686 GNU/Linux

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  • why can't I use "&&" in python to mean 'and'?

    - by Sergio Tapia
    Here's my code: # F. front_back # Consider dividing a string into two halves. # If the length is even, the front and back halves are the same length. # If the length is odd, we'll say that the extra char goes in the front half. # e.g. 'abcde', the front half is 'abc', the back half 'de'. # Given 2 strings, a and b, return a string of the form # a-front + b-front + a-back + b-back def front_back(a, b): # +++your code here+++ if len(a) % 2 == 0 && len(b) % 2 == 0: return a[:(len(a)/2)] + b[:(len(b)/2)] + a[(len(a)/2):] + b[(len(b)/2):] else: #todo! Not yet done. :P return I'm getting an error in the IF conditional. What am I doing wrong?

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  • Followed the official android documentations but still could not use SQLite in app

    - by user366539
    My DBHelper class public class DBHelper extends SQLiteOpenHelper { public DBHelper(Context context) { super(context,"SIMPLE_DB",null,1); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL("CREATE TABLE SIMPLE_TABLE ( " + "ID INTEGER PRIMARY KEY " + "DESC TEXT);"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { } } Activity class public class SimpleDatabase extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); DBHelper dbHelper = new DBHelper(this); SQLiteDatabase db = dbHelper.getReadableDatabase(); db.execSQL("INSERT INTO SIMPLE_TABLE VALUES (NULL, 'test');"); Cursor cursor = db.rawQuery("SELECT * FROM SIMPLE_TABLE", null); TextView text = (TextView)findViewById(R.id.textbox); text.setText(cursor.getString(0)); } } I figure it crashed (application has stopped unexpectedly!) at SQLiteDatabase db = ... because if I commented the code out from there to the end then it worked fine. But I have no idea whatsoever why it does that. Any help would be appreciated.

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