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• Need help for this syntax: "#define LEDs (char *) 0x0003010"

  - by Noge

  I'm doing programming of a softcore processor, Nios II from Altera, below is the code in one of the tutorial, I manage to get the code working by testing it on the hardware (DE2 board), however, I could not understand the code. #define Switches (volatile char *) 0x0003000 #define LEDs (char *) 0x0003010 void main() { while (1) *LEDs = *Switches; } What I know about #define is that, it is either used to define a constant, or a macro, but why in the above code, there are casting like, (char *) 0x0003010, in #define? why the 2 constants, Switches and LEDs act like a variable instead of a constant? Thanks in advance !

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• Find the "name" of a library (-L -l switches)

  - by sebastiangeiger

  Being fairly new to C++ I have a question bascially concerning the g++ compiler and especially the inclusion of libraries. Consider the following makefile: CPPFLAGS= -I libraries/boost_1_43_0-bin/include/ -I libraries/jpeg-8b-bin/include/ LDLIBS= libraries/jpeg-8b-bin/lib/libjpeg.a # LDLIBS= -L libraries/jpeg-8b-bin/lib -llibjpeg all: main main: main.o c++ -o main main.o $(LDLIBS) main.o: main.cpp c++ $(CPPFLAGS) -c main.cpp clean: rm -rf *.o main As you can see I declared the LDLIBS variable twice. My code is compiling and working if I use the makefile above. But if I deactivate the first LDLIBS entry and active the second one I get ld: library not found for -llibjpeg. I assume my libjpeg.a is just not called libjpeg but bears some different name. Is there a way to find out the name of a given "libraryfile" libsomething.a or libsomething.dyn?

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• How to deploy a Java Swing application with an embedded JavaDB database?

  - by Jonas

  I have implemented an Java Swing application that uses an embedded JavaDB database. The database need to be stored somewhere and the database tables need to be created at the first run. What is the preferred way to do these procedures? Should I always create the database in the local directory, and first check if the database file exist, and if it doesn't exist let the user create the tables (or at least show a message that the tables will be created). Or should I let the user choose a path? but then I have to save the path somewhere. Should I save the path with Preferences.systemRoot();, and check if that variable is set on startup? If the user choses a path and save it in the Preferences, can I get any problems with user permissions? or should it be safe wherever the user store the database? Or how do I handle this? Any other suggestions for this procedure?

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• MySQL parameter resource error

  - by Derek

  Here is my error: Warning: mysql_query() expects parameter 2 to be resource, null given... This refers to line 23 of my code which is: $result = mysql_query($sql, $connection) My entire query code looks like this: $query = "SELECT * from users WHERE userid='".intval( $_SESSION['SESS_USERID'] )."'"; $result = mysql_query($query, $connection) or die ("Couldn't perform query $query <br />".mysql_error()); $row = mysql_fetch_array($result); I don't have a clue what has happpened here. All I wanted to do was to have the value of the users 'fullname' displayed in the header section of my web page. So I am outputting this code immediately after to try and achieve this: echo 'Hello '; echo $row['fullname']; Before this change, I had it working perfectly, where the session variable of fullname was echoed $_SESSION['SESS_NAME']. However, because my user can update their information (including their name), I wanted the name displayed in the header to be updated accordingly, and not displaying the session value.

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• Why isn't my Ruby object deleted when the last reference goes out of scope?

  - by Andrew Clegg

  Hi gurus, I've found a weird effect when trying to track down a memory leak in a Rails app. Can anyone explain what's going on here? Save this script as a plain Ruby script (Rails not necessary): class Fnord def to_s 'fnord' end end def test f = Fnord.new end test GC.start sleep 2 ObjectSpace.each_object do |o| puts o if o.is_a? Fnord end When I run this via ruby 1.8.7 (2009-06-12 patchlevel 174) [i486-linux] I get the following: bash $ ruby var_test fnord Although the variable f is out of scope, there are no other references to the single Fnord object, and I've garbage collected, the object still seems to exist. Is this a nefarious memory leak of some sort, or am I completely missing something about Ruby? Further, if I change the test method to this: def test f = Fnord.new f = nil end I get no output. But surely this should not change the semantics here? Many thanks!

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• Cursors vs Procedures in SQL

  - by CogitoErgoSum

  So, I just learned about CURSORS but still don't exactly grasp them. What is the difference between a cursor and procedure or even a function? So far from the various examples (DECLARE CURSOR ... SELECT ... FROM ...) It seems at most its a variable to hold a query. Is the data real time, or a snapshot of when the cursor was declared? i.e. I have a table with one row and one col with a value of 2. I do DECLARE CURSOR ... SELECT * FROM table1 I then insert a new row with a value of 3. When I run the cursor, would I Just get the one row from before the cursor was declared, or both rows? Thanks

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• How to load an RSA key from binary data to an RSA structure using the OpenSSL C Library?

  - by Andreas Bonini

  Currently I have my private key saved in a file, private.key, and I use the following function to load it: RSA *r = PEM_read_RSAPrivateKey("private.key", NULL, NULL, NULL); This works perfectly but I'm not happy with the file-based format; I want to save my key in pure binary form (ie, no base64 or similar) in a char* variable and load/save the key from/to it. This way I have much more freedom: I'll be able to store the key directly into the application const char key[] { 0x01, 0x02, ... };, send it over a network socket, etc. Unfortunately though I haven't found a way to do that. The only way to save and load a key I know of reads/saves it to a file directly.

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• Strange behavior of for loop in scheduler_tick

  - by EpsilonVector

  I'm working on Linux kernel 2.4 (homework) and I inserted the following code into the scheduler_tick function: if (unlikely(rt_task(p)) || (p->policy==SCHED_PROD && p->time_ran>=p->process_expected_time)) { /* * RR tasks need a special form of timeslice management. * FIFO tasks have no timeslices. */ if ((p->policy == SCHED_RR || /*change*/p->policy==SCHED_PROD) && !--p->time_slice) { /*changes*/ if (p->policy == SCHED_PROD){ for (i=0; i<5000; i++){ printk("I'm leeching off SCHED_RR code! %d\n", i); } } /*end changes*/ The addition was added for debugging purposes. For some reason this causes very weird behavior: when a SCHED_PROD process triggers this code (and consequently the loop that follows) the loop counts to about 4600 normally, but then goes back to 4600 each time it counts to 4800, and gets stuck in an infinite loop. What's going on?? EDIT: The i variable is my own.

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• How to handle Clean URIs in Classic ASP using PATH_INFO?

  - by Mario

  I'm trying to handle Clean URIs in a Classic ASP application. In PHP, I was able to use URIs like http://example.com/index.php/foo/bar/baz and have /foo/bar/baz available in the PATH_INFO environment variable. (I usually add a rewrite rule so I do not need the index.php segment) However, I don't seem to be able to mimic this in Classic ASP. If I try http://example.com/index.asp/foo/bar/baz, I get a 404 error. Is there a way to add a path after the index.asp segment and get the PHP like behaviour in ASP? Note: I'm currently using the workaround of rewriting URLs of the form: http://example.com/foo/bar/baz/ to index.asp?path=/foo/bar/baz since I can't seem to get index.asp/foo/bar/baz to work.

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• Is there a way put a timestamp in the file header automatically when saving in Eclipse?

  - by George

  I am a PHP developer using Eclipse PDT. I would like a timestamp put automatically in my file headers whenever I save the file. Maybe as a replacement of a variable. Let's say I use this header in a file: /** * ${filename} * ${timestamp} */ When I save the file I would this to be replaced with: /** * Myfile.php * 4/20/2010 19:04 */ It would also be ok if there is a macro that would add a line at the very beginning of the file just containing a timestamp. Anybody with an idea? Regards, George

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• Preventing concurrent data modification in Web based app

  - by Manoj

  Hi, I am building a web app in Silverlight which allows users to view and edit a database. In order to prevent multiple users from editing the same data, I was thinking of implementing a lock and key mechanism, so that other users are made to wait when one particular user is editing the data. Is there any way in which we can have variable(flag specifying if a user is editing data) in the server which can be shared across multiple clients? Is there a better way to manage this type of conurrent data access issues?

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• Dynamically create and cast objects at runtime

  - by vaibhav bindroo

  Let's say we have 2 classes A and B public class A{ private int member1; A() { member1 = 10; } public getMember(){ return member1; } } Class B is also on the same lines except that its member variable is named member2 and gets intitialized to say 20 inside the constructor. My Requirement : At runtime , I get a string which contains a className ( could be A or B). I want to dynamically create an object of this class along with invoking the constructor. How can I achieve this . I don't want to use interfaces for common functionality of above classes Morever, later on I set the properties of this raw object using Propery Builder Bean Util class based on a list of columns . Class clazz = Class.forName("className"); Obj obj = clazz.newInstance(); How I can dynamically convert that obj to className object.

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• Shell - How to find directory of some command?

  - by Gabriel L. Oliveira

  I know that when you are on shell, the only commands that can be used are the ones that can be found on some directory set on PATH. Even I don't know how to see what dirs are on my PATH variable (and this is another good question that could be answered), what I'd like to know is: I come to shell and write: $ lshw I want to know a command on shell that can tell me WHERE this command is located. In other words, where this "executable file" is located? Something like: $ location lshw /usr/bin Anyone?

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• Breakdown of this Ruby code?

  - by randombits

  Would anyone be kind enough to dissect the merge! method? Its usage of conditions and variable assignment looks rather terse, and I'm having a difficult time following it. Would love to hear a Ruby-savvy developer break this apart. module ActiveRecord class Errors def merge!(errors, options={}) fields_to_merge = if only=options[:only] only elsif except=options[:except] except = [except] unless except.is_a?(Array) except.map!(&:to_sym) errors.entries.map(&:first).select do |field| !except.include?(field.to_sym) end else errors.entries.map(&:first) end fields_to_merge = [fields_to_merge] unless fields_to_merge.is_a?(Array) fields_to_merge.map!(&:to_sym) errors.entries.each do |field, msg| add field, msg if fields_to_merge.include?(field.to_sym) end end end end

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• How to deal with Rounding-off TimeSpan?

  - by infant programmer

  I take the difference between two DateTime fields, and store it in a TimeSpan variable, Now I have to round-off the TimeSpan by the following rules: if the minutes in TimeSpan is less than 30 then Minutes and Seconds must be set to zero, if the minutes in TimeSpan is equal to or greater than 30 then hours must be incremented by 1 and Minutes and Seconds must be set to zero. TimeSpan can also be a negative value, so in that case I need to preserve the sign.. I could be able to achieve the requirement if the TimeSpan wasn't a negative value, though I have written a code I am not happy with its inefficiency as it is more bulky .. Please suggest me a simpler and efficient method. Thanks regards,

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• When to pass by value?

  - by Dervin Thunk

  Dear all. I was wondering if there are examples of situations where you would purposefully pass an argument by value in C. Let me rephrase. When do you purposefully use C's pass-by-value for large objects? Or, when do you care that the object argument is fully copied in a local variable? EDIT: Now that I think about it, if you can avoid pointers, then do. Nowadays, "deep" copying is possible for mostly everything in small apps, and shallow copying is more prone to pointer bugs. Maybe.

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• Do I need multiple template specializations if I want to specialize for several kinds of strings?

  - by romkyns

  For example: template<typename T> void write(T value) { mystream << value; } template<> void write<const char*>(const char* value) { write_escaped(mystream, value); } template<> void write<char*>(char* value) { write_escaped(mystream, value); } template<> void write<std::string>(std::string value) { write_escaped(mystream.c_str(), value); } This looks like I'm doing it wrong, especially the two variants for const and non-const char*. However I checked that if I only specialize for const char * then passing a char * variable will invoke the non-specialized version, when called like this in VC++10: char something[25]; strcpy(something, "blah"); write(something); What would be the proper way of doing this?

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• iPhone UITableViewCell: repositioning the textLabel

  - by user359784

  Hello, I am new to iPhone development and I am currently working on a simple RSS reader app. The problem I am having is that I need to reposition the textLabel inside the UITableViewCells. I have tried setFrame or setCenter but it doesn't do anything. Does anyone know what I need to do inside the tableView:cellForRowAtIndexPath: method to reposition the textLabel at the top of the cell (x = 0, y = 0)? Thank you PS: The UITableViewCell is referenced by a variable called cell. I have tried [cell setFrame:CGRectMake(0, 0, 320, 20)] with no success.

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• How do I create multiple submit buttons for the same form in Rails?

  - by Angela

  I need to have multiple submit buttons. I have a form which creates an instance of Contact_Call. One button creates it as normal. The other button creates it but needs to have a different :attribute value from the default, and it also needs to set the attribute on a different, but related model used in the controller. How do I do that? I can't change the route, so is there a way to send a different variable that gets picked up by [:params]? And if I do then, what do I do in the controller, set up a case statement?

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• Object's field cannot be accessed after $.ajax call in success function - it is undefined

  - by dragonfly

  I have a $.ajax call and and server returns JSON. This is my call: var result; // tmp variable just for playing with Chrome console $.ajax({ type: "GET", url: "ashxJSON.ashx", data: { name: "some sample data" }, contentType: "application/json; charset=utf-8", dataType: "json", success: function (msg) { result = msg; console.log(msg); $("#output").append("<p>" + msg.message + "</p>"); }, error: function (jqXHR, textStatus, errorThrown) { console.log(textStatus); console.log(errorThrown); } }); Server returns exactly this string: { "messsage": "Hello World to ..."} And now, when I: console.log(msg) I see: Object messsage: "Hello World to..." proto: Object But when I access msg.message or msg["message"] I see: undefined What is wrong with me / that msg object?

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• Custom Grid LINQ to SQL help

  - by user488361

  Following is my custome cotrol grid... public partial class LinqGrid : UserControl { object tmpDataTable = new object(); public LinqGrid() { InitializeComponent(); } public void Bind(System.Data.Linq.Table listSource) where T : class { Project.dbClassesDataContext dbc = new Project.dbClassesDataContext(); tmpDataTable = listSource; var query = (from c in listSource select c); dgvRecords.DataSource = query.Take(10).ToList(); } private void btnNext_Click(object sender, EventArgs e) { // now what i have to do here if i want next 10 records.....means how to retrive tmpDataTable object here... ??? i can't find Type of variable....?? plz help me.... } }

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• Windows equivalent to this Makefile

  - by Sridhar Ratnakumar

  The advantage of writing a Makefile is that "make" is generally assumed to be present on the various Unices (Linux and Mac primarily). Now I have the following Makefile: PYTHON := python all: e installdeps e: virtualenv --distribute --python=${PYTHON} e installdeps: e/bin/python setup.py develop clean: rm -rf e As you can see this Makefile uses simple targets and variable substitution. Can this be achieved on Windows? By that mean - without having to install external tools (like cygwin make); perhaps make.cmd? Typing "make installdeps" for instance, should work both on Unix and Windows.

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• Looking for a free tool to visualize object relationships for C#

  - by vfilby

  Here is my ideal solution: a free tool that reads a .csporj or .sln and generates a pretty picture that shows all the objects and how they are related. By relationships, I don't mean inheritance but rather dependency. For example, if we have a Car object and Car has a member variable Wheel, I would like that Car depends on Wheel to be visualized in the graph. I know visual studio can do inheritance graphs, but that is only half of what I am looking for. Is what I am looking for possible? Are there any tools that do something similar? Related question for java: http://stackoverflow.com/questions/1824261/are-there-any-tools-to-visualize-the-objects-being-used-in-a-program

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• How to implement arrays in an interpreter?

  - by Ray

  I have managed to write several interpreters including Tokenizing Parsing, including more complicated expressions such as ((x+y)*z)/2 Building bytecode from syntax trees Actual bytecode execution What I didn't manage: Implementation of dictionaries/lists/arrays. I always got stuck with getting multiple values into one variable. My value structure (used for all values passed around, including variables) looks like this, for example: class Value { public: ValueType type; int integerValue; string stringValue; } Works fine with integers and strings, but how could I implement arrays? (From now on with array I mean arrays in my experimental language, not in C++) How can I fit the array concept into the Value class above? Is it possible? How should I make arrays able to be passed around just as you could pass around integers and strings in my language, using the class above? Accessing array elements or memory allocation wouldn't be the problem, I just don't know how to store them.

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• Pointers, links, object and reference count

  - by EugeneP

  String a = "a"; // allocate memory and write address of a memory block to a variable String b = "b"; // in a and b hold addresses b = a; // copy a address into b. // Now what? b value is completely lost and will be garbage collected //* next step a = null; // now a does not hold a valid address to any data, // still data of a object exist somewhere, yet we cannot get access to it. Correct me if there's a mistake somewhere in my reflexions. My question is: suppose anInstance object of type Instance has a property ' surname ' anInstance.getSurname() returns "MySurname". now String s = anInstance.getSurname(); anInstance = null; question is - is it true that getSurname value, namely MySurname will not be garbage collected because and only because it has active reference counter 0, and if other properties of anInstance have a zero reference counter, they'll be garbage collected?

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