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• Can LINQ expression classes implement the observer pattern instead of deferred execution?

  - by Tormod

  Hi. We have issues within an application using a state machine. The application is implemented as a windows service and is iteration based (it "foreaches" itself through everything) and there are myriads of instances being processed by the state machine. As I'm reading the MEAP version of Jon Skeets book "C# in Depth, 2nd ed", I'm wondering if I can change the whole thing to use linq expression instances so that guards and conditions are represented using expression trees. We are building many applications on this state machine engine and would probably greatly benefit from the new Expression tree visualizer in VS 2010 Now, simple example. If I have an expression tree where there is an OR Expression condition with two sub nodes, is there any way that these can implement the observer pattern so that the expression tree becomes event driven? If a condition change, it should notify its parent node (the OR node). Since the OR node then changes from "false" to "true", then it should notify ITS parent and so on. I love the declarative model of expression trees, but the deferred execution model works in opposite direction of the control flow if you want event based "live" conditions. Am I off on a wild goose chase here? Or is there some concept in the BCL that may help me achieve this?

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• numpy calling sse2 via ctypes

  - by Daniel

  Hello, In brief, I am trying to call into a shared library from python, more specifically, from numpy. The shared library is implemented in C using sse2 instructions. Enabling optimisation, i.e. building the library with -O2 or –O1, I am facing strange segfaults when calling into the shared library via ctypes. Disabling optimisation (-O0), everything works out as expected, as is the case when linking the library to a c-program directly (optimised or not). Attached you find a snipped which exhibits the delineated behaviour on my system. With optimisation enabled, gdb reports a segfault in __builtin_ia32_loadupd (__P) at emmintrin.h:113. The value of __P is reported as optimised out. test.c: #include <emmintrin.h> #include <complex.h> void test(const int m, const double* x, double complex* y) { int i; __m128d _f, _x, _b; double complex f __attribute__( (aligned(16)) ); double complex b __attribute__( (aligned(16)) ); __m128d* _p; b = 1; _b = _mm_loadu_pd( (double *) &b ); _p = (__m128d*) y; for(i=0; i<m; ++i) { f = cexp(-I*x[i]); _f = _mm_loadu_pd( (double *) &f ); _x = _mm_loadu_pd( (double *) &x[i] ); _f = _mm_shuffle_pd(_f, _f, 1); *_p = _mm_add_pd(*_p, _f); *_p = _mm_add_pd(*_p, _x); *_p = _mm_mul_pd(*_p,_b); _p++; } return; } Compiler flags: gcc -o libtest.so -shared -std=c99 -msse2 -fPIC -O2 -g -lm test.c test.py: import numpy as np import os def zerovec_aligned(nr, dtype=np.float64, boundary=16): '''Create an aligned array of zeros. ''' size = nr * np.dtype(dtype).itemsize tmp = np.zeros(size + boundary, dtype=np.uint8) address = tmp.__array_interface__['data'][0] offset = boundary - address % boundary return tmp[offset:offset + size].view(dtype=dtype) lib = np.ctypeslib.load_library('libtest', '.' ) lib.test.restype = None lib.test.argtypes = [np.ctypeslib.ctypes.c_int, np.ctypeslib.ndpointer(np.float64, flags=('C', 'A') ), np.ctypeslib.ndpointer(np.complex128, flags=('C', 'A', 'W') )] n = 13 y = zerovec_aligned(n, dtype=np.complex128) x = np.ones(n, dtype=np.float64) # x = zerovec_aligned(n, dtype=np.float64) # x[:] = 1. lib.test(n,x,y) My system: Ubuntu Linux i686 2.6.31-22-generic Compiler: gcc (Ubuntu 4.4.1-4ubuntu9) Python: Python 2.6.4 (r264:75706, Dec 7 2009, 18:45:15) [GCC 4.4.1] Numpy: 1.4.0 I have taken provisions (cf. python code) that y is aligned and the alignment of x should not matter (I think; explicitly aligning x does not solve the problem though). Note also that i use _mm_loadu_pd instead of _mm_load_pd when loading b and f. For the C-only version _mm_load_pd works (as expected). However, when calling the function via ctypes using _mm_load_pd always segfaults (independent of optimisation). I have tried several days to sort out this issue without success ... and I am on the verge beating my monitor to death. Any input welcome. Daniel

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• dynamic row height

  - by Prasanna Venkatesh

  static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@""]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } //cell.backgroundView = [[[CustomCell alloc] init] autorelease]; cell.selectedBackgroundView = [[[CustomCell alloc] init] autorelease]; // At end of function, right before return cell: cell.textLabel.backgroundColor = [UIColor clearColor]; // Configure the cell. UILabel *myLabel1 = [[UILabel alloc] initWithFrame:CGRectMake(-30, 3, 300, 22)]; UILabel *myLabel2 = [[UILabel alloc] initWithFrame:CGRectMake(10, 22, 310, 200)]; UILabel *myLabel3 = [[UILabel alloc] initWithFrame:CGRectMake(0, 170, 300, 20)]; Book *aBook = [appDelegate.books objectAtIndex:indexPath.row]; myLabel1.text=aBook.title; myLabel2.text=aBook.description; myLabel3.text=aBook.pubDate; NSString *desc = aBook.description; if ([desc isEqualToString:nil]) { NSLog(@"nullll lll "); } //myLabel2.textAlignment=UITextAlignmentCenter; myLabel2.numberOfLines=5; myLabel2.textColor=[UIColor blueColor]; myLabel2.lineBreakMode=UILineBreakModeWordWrap; myLabel2.font=[UIFont systemFontOfSize:14]; myLabel3.numberOfLines=1; myLabel1.numberOfLines=1; myLabel1.textColor=[UIColor redColor]; myLabel1.font=[UIFont systemFontOfSize:20]; myLabel1.shadowColor=[UIColor redColor]; myLabel1.backgroundColor=[UIColor grayColor]; [cell.contentView addSubview:myLabel1]; [cell.contentView addSubview:myLabel2]; [cell.contentView addSubview:myLabel3]; hi guys! i have this following code, i want to display this from xml file. now its working but static row height. if the xml file dont have data then it leaves it as blank. so i want to change row height according to the data i provide using the mylabel1,2,3.text

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• Drag and Drop in Silverlight with F# and Asynchronous Workflows

  - by knotig

  Hello everyone! I'm trying to implement drag and drop in Silverlight using F# and asynchronous workflows. I'm simply trying to drag around a rectangle on the canvas, using two loops for the the two states (waiting and dragging), an idea I got from Tomas Petricek's book "Real-world Functional Programming", but I ran into a problem: Unlike WPF or WinForms, Silverlight's MouseEventArgs do not carry information about the button state, so I can't return from the drag-loop by checking if the left mouse button is no longer pressed. I only managed to solve this by introducing a mutable flag. Would anyone have a solution for this, that does not involve mutable state? Here's the relevant code part (please excuse the sloppy dragging code, which snaps the rectangle to the mouse pointer): type MainPage() as this = inherit UserControl() do Application.LoadComponent(this, new System.Uri("/SilverlightApplication1;component/Page.xaml", System.UriKind.Relative)) let layoutRoot : Canvas = downcast this.FindName("LayoutRoot") let rectangle1 : Rectangle = downcast this.FindName("Rectangle1") let mutable isDragged = false do rectangle1.MouseLeftButtonUp.Add(fun _ -> isDragged <- false) let rec drag() = async { let! args = layoutRoot.MouseMove |> Async.AwaitEvent if (isDragged) then Canvas.SetLeft(rectangle1, args.GetPosition(layoutRoot).X) Canvas.SetTop(rectangle1, args.GetPosition(layoutRoot).Y) return! drag() else return() } let wait() = async { while true do let! args = Async.AwaitEvent rectangle1.MouseLeftButtonDown isDragged <- true do! drag() } Async.StartImmediate(wait()) () Thank you very much for your time!

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• Protected and Private methods

  - by cabaret

  I'm reading through Beginning Ruby and I'm stuck at the part about private and protected methods. This is a newbie question, I know. I searched through SO for a bit but I couldn't manage to find a clear and newbie-friendly explanation of the difference between private and protected methods. The book gives two examples, the first one for private methods: class Person def initialize(name) set_name(name) end def name @first_name + ' ' + @last_name end private def set_name(name) first_name, last_name = name.split(/\s+/) set_first_name(first_name) set_last_name(last_name) end def set_first_name(name) @first_name = name end def set_last_name(name) @last_name = name end end In this case, if I try p = Person.new("Fred Bloggs") p.set_last_name("Smith") It will tell me that I can't use the set_last_name method, because it's private. All good till there. However, in the other example, they define an age method as protected and when I do fred = Person.new(34) chris = Person.new(25) puts chris.age_difference_with(fred) puts chris.age It gives an error: :20: protected method 'age' called for #<Person:0x1e5f28 @age=25> (NoMethodError) I honestly fail to see the difference between the private and protected methods, it sounds the same to me. Could someone provide me with a clear explanation so I'll never get confused about this again? I'll provide the code for the second example if necessary.

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• C socket: problem with connect() and/or accept() between clients. 111: Connection refused

  - by Fantastic Fourier

  Hello ladies and gents, I'm having a bit of problem with accept(). I have a multiple clients and one server. The clients can connect and communicate just fine with server. But at one point, I need some clients to be directly connected to each other and I'm having a bit of difficulty there. The clients have bunch of threads going on, where one of them is handle_connection() and it has a while(1), looping forever to listen() and accept() whatever incoming connections. Whenever a client tries to connect() to other client, connect() returns an error, 111: Connection Refused. I know I have the right IP address and right port (I have specified a port just for between-client connections). The client that is waiting for connection doesn't notice anything, no new connection, nada. I copied some parts of the code, in hopes that someone can point out what I'm doing wrong. Thanks for any inputs! This is all client side code. void * handle_connections(void * arg) is a thread that loops forever to accept() any incoming connections. My server has a very similar thang going on and it works very well. (not sure why it doesn't work here..) This is the part of client that is waiting for a new incoming connection. int handle_request(void * arg, struct message * msg) is called at one point during program and tries to connect to a client that is specified in struct message * msg which includes struct sockaddr_in with IP address and port number and whatever. #define SERVER_PORT 10000 #define CLIENT_PORT 3456 #define MAX_CONNECTION 20 #define MAX_MSG 50 void * handle_connections(void * arg) { struct fd_info * info; struct sockaddr_in client_address; struct timeval timeout; fd_set readset, copyset; bzero((char * ) &client_address, sizeof(client_address)); // copy zeroes into string client_address.sin_family = AF_INET; client_address.sin_addr.s_addr = htonl(INADDR_ANY); client_address.sin_port = htons(CLIENT_PORT); sockfd = socket(AF_INET, SOCK_STREAM, 0); rv = listen(sockfd,MAX_CONNECTION); while(1) { new_sockfd = accept(sockfd, (struct sockaddr *) &client_address, &client_addr_len); //blocks if (new_sockfd < 0) { printf("C: ERROR accept() %i: %s \n", errno, strerror(errno)); sleep(2); } else { printf("C: accepted\n"); FD_SET(new_sockfd, &readset); // sets bit for new_sockfd to list of sockets to watch out for if (maxfd < new_sockfd) maxfd = new_sockfd; if (minfd > new_sockfd) minfd = new_sockfd; } //end if else (new_sockfd) } // end of the forever while loop } int handle_request(void * arg, struct message * msg) { char * cname, gname, payload; char * command[3]; int i, rv, sockfd, client_addr_len; struct sockaddr_in client_address; struct fd_info * info; info = (struct fd_info *) arg; sockfd = info->sock_fd; sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd == -1) { printf("HR: ERROR socket() %i: %s \n", errno, strerror(errno)); break; } else if (sockfd > 0) { printf("HR: new socks is %i \n", sockfd); printf("HR: sin_family is %i: %i\n", msg->peer.client_address.sin_family, msg->peer.client_address.sin_port); //************************************************************* //this is the part that returns error 111: Connection refused!!! //************************************************************* rv = connect(sockfd, (struct sockaddr *) &msg->peer.client_address, sizeof(struct sockaddr)); if (rv == -1) { printf("HR: ERROR: connect() %i: %s \n", errno, strerror(errno)); printf("HR: at %li \n", msg->peer.client_address.sin_addr.s_addr); break; } else if (rv > 0) { info->max_fd = sockfd; printf("HR: connected successfully!! \n"); } } }

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• Getting my head around object oriented programing

  - by nLL

  I am entry level .Net developer and using it to develop web sites. I started with classic asp and last year jumped on the ship with a short C# book. As I developed I learned more and started to see that coming from classic asp I always used C# like scripting language. For example in my last project I needed to encode video on the webserver and wrote a code like public class Encoder { Public static bool Encode(string videopath) { ...snip... return true; } } While searching samples related to my project I’ve seen people doing this public class Encoder { Public static Encode(string videopath) { EncodedVideo encoded = new EncodedVideo(); ...snip... encoded.EncodedVideoPath = outputFile; encoded.Success = true; ...snip... } } public class EncodedVideo { public string EncodedVideoPath { get; set; } public bool Success { get; set; } } As I understand second example is more object oriented but I don’t see the point of using EncodedVideo object. Am I doing something wrong? Does it really necessary to use this sort of code in a web app?

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• How to manipulate *huge* amounts of data

  - by Alejandro

  Hi there! I'm having the following problem. I need to store huge amounts of information (~32 GB) and be able to manipulate it as fast as possible. I'm wondering what's the best way to do it (combinations of programming language + OS + whatever you think its important). The structure of the information I'm using is a 4D array (NxNxNxN) of double-precission floats (8 bytes). Right now my solution is to slice the 4D array into 2D arrays and store them in separate files in the HDD of my computer. This is really slow and the manipulation of the data is unbearable, so this is no solution at all! I'm thinking on moving into a Supercomputing facility in my country and store all the information in the RAM, but I'm not sure how to implement an application to take advantage of it (I'm not a professional programmer, so any book/reference will help me a lot). An alternative solution I'm thinking on is to buy a dedicated server with lots of RAM, but I don't know for sure if that will solve the problem. So right now my ignorance doesn't let me choose the best way to proceed. What would you do if you were in this situation? I'm open to any idea. Thanks in advance!

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• Beginning Haskell: "not in scope" Unprecedented error

  - by user1071838

  So I just started learning Haskell, and this (http://learnyouahaskell.com) nifty book is giving a lot of help. So yesterday I wrote in a text file doubleMe x = x + x and saved it as double.hs. So after saving that I open up my command prompt, CD to the right folder, type in "ghci" to get haskell started, and then type in >doubleMe 5 10 and everything seems to work. Now today, I do the same thing and this happens (actual copy paste from command line) . . . C:\Users\myName\haskell>ghci GHCi, version 7.0.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package ffi-1.0 ... linking ... done. Prelude> :l double.hs [1 of 1] Compiling Main ( double.hs, interpreted ) Ok, modules loaded: Main. *Main> doubleMe 5 <interactive>:1:1: Not in scope: `doubleMe' So basically, everything was working fine, but now haskell can't find the function I wrote in double.hs. Can anyone tell what is going on? I'm pretty lost and confused. This is just a guess but does it have to do with *Main at all? Thanks for the help.

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• Summation loop program in Pascal

  - by user2526598

  I am having a bit of an issue with this problem. I am taking a Pascal programming class and this problem was in my logic book. I am required to have the user enter a series of (+) numbers and once he/she enters a (-) number, the program should find the sum of all the (+) numbers. I accomplished this, but now I am attempting part two of this problem, which requires me to utilize a nested loop to run the program x amount of times based on the user's input. The following code is what I have so far and honestly I am stumped: program summation; //Define main program's variables var num, sum, numRun : integer; //Design procedure that will promt user for number of runs procedure numRunLoop ( var numRun : integer ); begin writeln('How many times shall I run this program?'); readln(numRun); end; //Design procedure that will sum a series of numbers //based on user input procedure numPromptLoop( numRun : integer; var num : integer ); var count : integer; begin //Utilize for to establish run limit for count := 1 to numRun do begin //Use repeat to prompt user for numbers repeat writeln('Enter a number: '); readln(num); //Tells program when to sum if num >= 0 then sum := sum + num; until num < 0; end; end; //Design procedure that will display procedure addItion( sum : integer ); begin writeln('The sum is; ', sum); end; begin numRunLoop(numRun); numPromptloop(numRun, num); addItion(sum); readln(); end.

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• accessing a value of a nested hash

  - by st

  Hello! I am new to perl and I have a problem that's very simple but I cannot find the answer when consulting my perl book. When printing the result of Dumper($request); I get the following result: $VAR1 = bless( { '_protocol' => 'HTTP/1.1', '_content' => '', '_uri' => bless( do{\(my $o = 'http://myawesomeserver.org:8081/counter/')}, 'URI::http' ), '_headers' => bless( { 'user-agent' => 'Mozilla/5.0 (X11; U; Linux i686; en; rv:1.9.0.4) Gecko/20080528 Epiphany/2.22 Firefox/3.0', 'connection' => 'keep-alive', 'cache-control' => 'max-age=0', 'keep-alive' => '300', 'accept' => 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8', 'accept-language' => 'en-us,en;q=0.5', 'accept-encoding' => 'gzip,deflate', 'host' => 'localhost:8081', 'accept-charset' => 'ISO-8859-1,utf-8;q=0.7,*;q=0.7' }, 'HTTP::Headers' ), '_method' => 'GET', '_handle' => bless( \*Symbol::GEN0, 'FileHandle' ) }, 'HTTP::Server::Simple::Dispatched::Request' ); How can I access the values of '_method' ('GET') or of 'host' ('localhost:8081'). I know that's an easy question, but perl is somewhat cryptic at the beginning. Thank you, St.

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• Access 2007 and Special/Unicode Characters in SQL

  - by blockcipher

  I have a small Access 2007 database that I need to be able to import data from an existing spreadsheet and put it into our new relational model. For the most part this seems to work pretty well. Part of the process is attempting to see if a record already exists in a target table using SQL. For example, if I extract book information out of the current row in the spreadsheet, it may contain a title and abstract. I use SQL to get the ID of a matching record, if it exists. This works fine except when I have data that's in a non-English language. In this case, it seems that there is some punctuation that is causing me problems. At least I think it's punctuation as I do have some fields that do not have punctuation and are non-English that do not give me any problems. Is there a built-in function that can escape these characters? Currently I have a small function that will escape the single quote character, but that isn't enough. Or, is there a list of Unicode characters that can interfere with how SQL wants data quoted? Thanks in advance.

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• In Java it seems Public constructors are always a bad coding practice

  - by Adam Gent

  This maybe a controversial question and may not be suited for this forum (so I will not be insulted if you choose to close this question). It seems given the current capabilities of Java there is no reason to make constructors public ... ever. Friendly, private, protected are OK but public no. It seems that its almost always a better idea to provide a public static method for creating objects. Every Java Bean serialization technology (JAXB, Jackson, Spring etc...) can call a protected or private no-arg constructor. My questions are: I have never seen this practice decreed or written down anywhere? Maybe Bloch mentions it but I don't own is book. Is there a use case other than perhaps not being super DRY that I missed? EDIT: I explain why static methods are better. .1. For one you get better type inference. For example See Guava's http://code.google.com/p/guava-libraries/wiki/CollectionUtilitiesExplained .2. As a designer of the class you can later change what is returned with a static method. .3. Dealing with constructor inheritance is painful especially if you have to pre-calculate something.

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• What should a self-taught programmer with no degree learn/read?

  - by sjbotha

  I am a self-taught programmer and I do do not have any degrees. I started pretty young and I've got about 7 years of actual programming work experience. I believe I'm a pretty good programmer, but I admit that I have not played much with algorithms or delved into any really low-level aspects of programming such as how compilers work. I have worked with other programmers with and without degrees. Some were good and some not; having a degree didn't seem to make any difference as to which pot they fell into. Since then I've come to realize that it does depend on the school where the degree is obtained. Some people suggest that you really should get a degree; that there are things you'll learn in the process that you won't learn in the real world. Of course there is personal growth and discipline learned from completing a task of that magnitude, but let's just concentrate on the technical knowledge. What would I have been taught in a GOOD CS course that would aid me today and what can I read to fill the gap? I've heard the book "Algorithms" mentioned and I plan on reading that. What other books would you recommend? Edit: Clarification on 'actual work experience': Have worked for 2 small companies on teams with fewer than 5 people. About 2 years experience with Perl, Python, PHP, C, C++. About 5 years experience in Java, Applets, RMI, T-SQL, PL/SQL, VB6. 7 years experience in HTML, Javascript, bash, SQL. Most recently in Java designed and helped build an N-tier Java app with web frontend and RMI.

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• PHP - DOM class - numbered entities and encodings problem

  - by user343607

  Hi guys, I'm having some difficult with PHP DOM class. I am making a sitemap script, and I need the output of $doc-saveXML() to be like <?xml version="1.0" encoding="UTF-8"?> <root> <url> <loc>http://www.somesite.com/servi&#xE7;os/redesign</loc> </url> </root> or <?xml version="1.0" encoding="UTF-8"?> <root> <url> <loc>http://www.somesite.com/servi&#231;os/redesign</loc> </url> </root> but I am getting: <?xml version="1.0" encoding="UTF-8"?> <root> <url> <loc>http://www.somesite.com/servi&amp;#xE7;os/redesign</loc> </url> </root> This is the closet I could get, using a replace named to numbered entities function. I was also able to reproduce <?xml version="1.0" ?> <root> <url> <loc>http://www.somesite.com/servi&amp;#xE7;os/redesign</loc> </url> </root> But without the encoding specified. The best solution (the way I think the code should be written) would be: <?php $myArray = array(); // do some stuff to populate the with URL strings $doc = new DOMDocument('1.0', 'UTF-8'); // here we modify some property. Maybe is the answer I am looking for... $urlset = doc->createElement("urlset"); $urlset = $doc->appendChild($urlset); foreach($myArray as $address) { $url = $doc->createElement("url"); $url = $urlset->appendChild($url); $loc = $doc->createElement("loc"); $loc = $url->appendChild($loc); $valueContent = $doc->createTextNode($value); $valueContent = $loc->appendChild($address); } echo $doc->saveXML(); ?> Notes: Server response header contains charset as UTF-8; PHP script is saved in UTF-8; URLs read are UTF-8 strings; Above script contains encoding declaration on DOMDocument constructor, and does not use any convert functions, like htmlentities, urlencode, utf8_encode... I've tried changing the DOMDocument properties DOMDocument::$resolveExternals and DOMDocument::$substituteEntities values. None combinations worked. And yes, I know I can made all process without specifying the character set on DOMDocument constructor, dump string content into a variable and make a very simple string substitution with string replace functions. This works. But I would like to know where I am slipping, how can this be made using native API's and settings, or even if this is possible. Thanks in advance.

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• Tablet interface for the physically disabled?

  - by Glenn

  My sister has Cerebral Palsy, which in her case means she has only gross motor control and her speech is slurred. Implications should be obvious: traditional computer/phone/tablet interfaces won't work for her and she can't speak clearly enough for speech recognition software to help her at all. She enjoys reading but has difficulty holding the book and/or turning a page. There are a few options for helping her use a computer, but nothing for tablets or eReaders. That's where you come in. I would like to make (or buy, if such a thing exists) a better interface to an Android tablet that would work for someone with little to no physical dexterity or speech ability. I'd also be interested in work on the Kindle or iPad, but I'm most familiar with Android so I'm starting there. I know Android has Bluetooth capability. Is it possible to interface a joystick to control the Android device? By "control", I mean the entire operating system - selecting an app, launching it, controlling the menus, etc. I want to give her control over the whole thing, not just a specific app. On a PC this can be accomplished by creating a generic USB HID interface and an arcade joystick to move the mouse over the screen and click on thigns. Is it possible to do something like that in Android? Any help you can offer would be greatly appreciated. Thanks!

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• How to do binding programmically?

  - by user175908

  Hello, Could anyone identify the problem in this code? (I'm kinda newbie in WPF bindings.) This code executes after chart is loaded when I click a button: I get this error: Update: I dont get that error anymore. Thanks to Tomas. Now no error occur but chart looks completely blank (no columns) Update: Code now looks like this: // create a very simple DataSet var dataSet = new DataSet("MyDataSet"); var table = dataSet.Tables.Add("MyTable"); table.Columns.Add("Name"); table.Columns.Add("Price"); table.Rows.Add("Brick", 1.5d); table.Rows.Add("Soap", 4.99d); table.Rows.Add("Comic Book", 0.99d); // chart series var series = new ColumnSeries() { IndependentValueBinding = new Binding("[Name]"), // How to deal with DependentValueBinding = new Binding("[Price]"), // these two? ItemsSource = dataSet.Tables[0].DefaultView // or maybe I do mistake here? }; // ---------- set additional binding as adviced ------------------ series.SetBinding(ColumnSeries.ItemsSourceProperty, new Binding()); // chart stuff MyChart.Series.Add(series); MyChart.Title = "Names 'n Prices"; // some code to remove legend var style = new Style(typeof(Control)); style.Setters.Add(new Setter(LegendItem.TemplateProperty, null)); MyChart.LegendStyle = style; XAML: <Window x:Class="BindingzTest.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="606" Width="988" xmlns:charting="clr-namespace:System.Windows.Controls.DataVisualization.Charting;assembly=System.Windows.Controls.DataVisualization.Toolkit"> <Grid Name="LayoutRoot"> <charting:Chart Name="MyChart" Margin="0,0,573,0" Height="289" VerticalAlignment="Top" /> <Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="272,361,0,0" Name="button1" VerticalAlignment="Top" Width="75" Click="chart1_Loaded" /> </Grid> Thanks for help in advance once more.

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• How to learn how to program?

  - by twinbornJoint

  I would like to know the best methods for learning to program. I've been directed towards the Python language because I was told it is good for beginners. I ultimately want to make games for OS X/iPhone. My problem is that I understand what I read but I can't apply my knowledge to anything. I am a programming noob. Should I stick with Python? (is there a better language I should be learning?) Where can I learn programming theory? I get very hyper when reading my book sometimes, any tips on staying calm and focusing? What are effective ways to learn how to program? Are there standard exercises for programming? (I feel solving problems helps my understanding immensely) Ultimately I feel like I am in a never ending tunnel that leads me no where. It feels like I am just completely unable to pursue anything in the world of programming, yet it is something I want to do very much. Thanks.

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• Design of std::ifstream class

  - by Nawaz

  Those of us who have seen the beauty of STL try to use it as much as possible, and also encourage others to use it wherever we see them using raw pointers and arrays. Scott Meyers have written a whole book on STL, with title Effective STL. Yet what happened to the developers of ifstream that they preferred char* over std::string. I wonder why the first parameter of ifstream::open() is of type const char*, instead of const std::string &. Please have a look at it's signature: void open(const char * filename, ios_base::openmode mode = ios_base::in ); Why this? Why not this: void open(const string & filename, ios_base::openmode mode = ios_base::in ); Is this a serious mistake with the design? Or this design is deliberate? What could be the reason? I don't see any reason why they have preferred char* over std::string. Note we could still pass char* to the latter function that takes std::string. That's not a problem! By the way, I'm aware that ifstream is a typedef, so no comment on my title.:P. It looks short that is why I used it. The actual class template is : template<class _Elem,class _Traits> class basic_ifstream;

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• details in one Row without any redundancy in the CATID

  - by alkitbi

  $query1 = "select * from linkat_link where emailuser = '$email2' or linkname ='$domain_name2' ORDER BY date desc LIMIT $From,$PageNO"; id   catid      discription            price ------------------------------------ 1         1     domain name     100 2         1      book                  50 3        2      hosting               20 4        2      myservice           20 in this script i have one problem , if i have an ID for Each Cantegory , i have some duplicated CATID which has different content but shares the same CATID, i need to make any duplicated CATID to show in one , and all the discription will be in the same line (Cell) on the same row . So Each CatID will have all the details in one Row without any redundancy in the CATID

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• Java Concurrency in practice sample question

  - by andy boot

  I am reading "Java Concurrency in practice" and looking at the example code on page 51. According to the book this piece of code is at risk of of failure if it has not been published properly. Because I like to code examples and break them to prove how they work. I have tried to make it throw an AssertionError but have failed. (Leading me to my previous question) Can anyone post sample code so that an AssertionError is thrown? Rule: Do not modify the Holder class. public class Holder{ private int n; public Holder(int n){ this.n = n; } public void assertSanity(){ if (n != n) { throw new AssertionError("This statement is false"); } } } I have modified the class to make it more fragile but I still can not get an AssertionError thrown. class Holder2{ private int n; private int n2; public Holder2(int n) throws InterruptedException{ this.n = n; Thread.sleep(200); this.n2 = n; } public void assertSanity(){ if (n != n2) { throw new AssertionError("This statement is false"); } } } Is it possible to make either of the above classes throw an AssertionError? Or do we have to accept that they may occasionally do so and we can't write code to prove it?

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• Is CakePhp 'standards compliant' when generating HTML, Forms, etc?

  - by dtj

  So I've been reading a lot of "Designing with Web Standards" and really enjoying it. I'm a big CakePhp user, and as I look at the source for various form elements that Cake creates with its FormHelper, I see all sorts of extraneous In the book, he promotes semantic HTML, and writing your markup as simple / generic as possible. So my question is, am I better writing my own HTML in these situations? I really want to work in compliance with XHTML and CSS standards, and it seems I'd spend just as much time (if not more) cleaning up Cakes HTML, when I could just write my own thoughts? p.s. Here's an example in an out of the box form that CakePhp generates using the FormHelper <form id="CompanyAddForm" method="post" action="/omni_cake/companies/add" accept-charset="utf-8"><div style="display:none;"><input type="hidden" name="_method" value="POST" /></div> <div class="input text required"><label for="CompanyName">Name</label><input name="data[Company][name]" type="text" maxlength="50" id="CompanyName" /></div> <div class="input text required"><label for="CompanyWebsite">Website</label><input name="data[Company][website]" type="text" maxlength="50" id="CompanyWebsite" /></div> <div class="input textarea"><label for="CompanyNotes">Notes</label><textarea name="data[Company][notes]" cols="30" rows="6" id="CompanyNotes" ></textarea></div> <div class="submit"><input type="submit" value="Submit" /></div></form>

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• Question about compilers and how they work

  - by Marin Doric

  This is the C code that frees memory of a singly linked list. It is compiled with Visual C++ 2008 and code works as it should be. /* Program done, so free allocated memory */ current = head; struct film * temp; temp = current; while (current != NULL) { temp = current->next; free(current); current = temp; } But I also encountered ( even in a books ) same code written like this: /* Program done, so free allocated memory */ current = head; while (current != NULL) { free(current); current = current->next; } If I compile that code with my VC++ 2008, program crashes because I am first freeing current and then assigning current-next to current. But obviously if I compile this code with some other complier ( for example, compiler that book author used ) program will work. So question is, why does this code compiled with specific compiler work? Is it because that compiler put instructions in binary file that remember address of current-next although I freed current and my VC++ doesn't. I just want to understand how compilers work.

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• Inconsistent behavior working with "Flex on Rails" example.

  - by kmontgom

  I'm experimenting with Flex and Rails right now (Rails is cool). I'm following the examples in the book "Flex on Rails", and I'm getting some puzzling and inconsistent behavior. Heres the Flex MXML: <mx:HTTPService id="index" url="http://localhost:3000/people.xml" resultFormat="e4x" /> <mx:DataGrid dataProvider="{index.lastResult.person}" width="100%" height="100%"> <mx:columns> <mx:DataGridColumn headerText="First Name" dataField="first-name"/> <mx:DataGridColumn headerText="Last Name" dataField="last-name"/> </mx:columns> </mx:DataGrid> <mx:Script> <![CDATA[ import mx.controls.Alert; private function main():void { Alert.show( "In main()" ); } ]]> </mx:Script> When I run the app from my IDE (Amythyst beta, also cool), the DataGrid appears, but is not populated. The Alert.show() also triggers. When I go out to a web browser and manually enter the url (http://localhost:3000/people.xml), the Mongrel console shows the request coming through and the browser shows the web response. No exceptions or other error messages occur. Whats the difference? Do I need to alter some OS setting? I'm using Win7 on an x64 machine.

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• How to obtain the panel within a treeview (WPF)

  - by sperling

  How can one obtain the panel that is used within a TreeView? I've read that by default TreeView uses a VirtualizingStackPanel for this. When I look at a TreeView template, all I see is <ItemsPresenter />, which seems to hide the details of what panel is used. Possible solutions: 1) On the treeview instance ("tv"), from code, do this: tv.ItemsPanel. The problem is, this does not return a panel, but an ItemsPanelTemplate ("gets or sets the template that defines the panel that controls the layout of the items"). 2) Make a TreeView template that explicitly replaces <ItemsPresenter /> with your own ItemsControl.ItemsPanel. I am providing a special template anyways, so this is fine in my scenario. Then give a part name to the panel that you place within that template, and from code you can obtain that part (i.e. the panel). The problem with this? see below. (I am using a control named VirtualTreeView which is derived from TreeView, as is seen below): , use following: -- [sorry folks about poor formatting here, this is my first post, I tried 4 spaces for code... doesn't seem to work?] [I stripped out all clutter here for visibility...] The problem with this is: this immediately overrides any TreeView layout mechanism. Actually, you just get a blank screen, even when you have TreeViewItems filling the tree. Well, the reason I want to get a hold of the panel is to take some part in the MeaureOverride, but without going into all of that, I certainly do not want to rewrite the book of how to layout a treeview. I.e., doing this the step #2 way seems to invalidate the point of even using a TreeView in the first place. Sorry if there is some confusion here, thanks for any help you can offer.

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