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• C++ open() fails for no apparant reason

  - by jondoe

  The following code: char filename[64]; ifstream input; cout << "Please enter the filename: " << endl; cin >> filename; input.open(filename); if (!input.is_open()) { cout << "Opening file " << filename << " failed." << endl; exit(1); } fails, it enters the if() and exits. What could possibly be the cause for this? I'm using Microsoft Visual C++. When I hardcoded the filename as a constant it instead ended up garbled: http://pici.se/pictures/CNQEnwhgo.png Suggestions?

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• What is the difference between these two ways of creating NSStrings?

  - by adame

  NSString *myString = @"Hello"; NSString *myString = [NSString stringWithString:@"Hello"]; I understand that using method (1) creates a pointer to a string literal that is defined as static memory (and cannot be deallocated) and that using (2) creates an NSString object that will be autoreleased. Is using method (1) bad? What are the major differences? Is there any instances where you would want to use (1)? Is there a performance difference? P.S. I have searched extensively on Stack Overflow and while there are questions on the same topic, none of them have answers to the questions I have posted above.

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• Why does this code crash?

  - by user146780

  The following code causes a stack overflow but I don't see why... int _tmain(int argc, _TCHAR* argv[]) { cout << "start"; char bmp[1024][768][3]; for (int p = 0; p < 9000; ++p) { for(int i = 0; i < 1024; ++i) { for(int j = 0; j < 768; ++j) { bmp[i][j][0] = 20; } } } cout << "Stop"; return 0; } Thanks

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• In PHP can I check a boolean on a function call?

  - by Chris

  I have a function which checks the passed value and returns false or true, if false I want it to add something to an array. The code I've written is below. if(!check_input($_POST['username'])){ $errors[] = "Username"; } Right now it adds to my array anyway, regardless of what is entered in the form. Is the way I've written that the correct way to check if the return from check_input() is false? I've checked the function's logic by altering the returns to echoes and it's returning the correct value, I'm just not sure if I'm checking it wrong. I'd previously attempted to write it as $X=check_input etc, and then if(check_value == false) but that doesn't seem to give me the desired result either. Hmmm a quick pointer please!

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• Multiple selection in a TreeView

  - by Frederick

  I am using a Windows Forms TreeView control in my program. I would like to allow the user to select multiple nodes at the same level by dragging their mouse pointer around (also called a "lasso" selection). I don't think a standard TreeView allows that. My question is what would be the best way to achieve this? Do I have to write custom selection behaviour of my own in perhaps a custom or derived control? Where do I start? I don't need a detailed explanation. Just a small nudge in the right direction.

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• Writing different structs to a file in C++? [on hold]

  - by user58053

  I need a way to write structures of three different kinds to a binary file, which later has to be searched. (As in, for example, struct A has two fields, an int and a char; struct B has int and a long; I need to output all structures whose int equals the one given from keyboard). I understand how to write structs of the same kind to a file and how to search them, but here I am just lost, best thing I came up with is declaring a struct containing all possibly needed fields and leaving the ones I don't need empty, but it really feels wrong, there HAS to be a better way to do that. I've read about binary files and could not find anything relevant, most examples and tutorials deal with writing one data type. Could anyone point me in the right direction? EDIT: I am looking for what @Jerry_coffin called database mode, and will probably use one of the existing database systems for that, best way to go, probably. Thank you everybody for the suggestions

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• Consolidating separate Loan, Purchase & Sales tables into one transaction table.

  - by Frank Computer

  INFORMIX-SE with ISQL 7.3: I have separate tables for Loan, Purchase & Sales transactions. Each tables rows are joined to their respective customer rows by: customer.id [serial] = loan.foreign_id [integer]; = purchase.foreign_id [integer]; = sale.foreign_id [integer]; I would like to consolidate the three tables into one table called "transaction", where a column "transaction.trx_type" [char(1)] {L=Loan, P=Purchase, S=Sale} identifies the transaction type. Is this a good idea or is it better to keep them in separate tables? Storage space is not a concern, I think it would be easier programming & user=wise to have all types of transactions under one table.

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• Make object by it's name

  - by Ockonal

  Hello, is it possible to return exemplar of object using passed type name (string) in c++? I have some base abstract class Base and a few derivates. Example code: class Base { /* ... */ }; class Der1 : public Base { /* ... */ }; class Der2 : public Base { /* ... */ }; And I need function like: Base *objectByType(const std::string &name); Number of derivates classes are changeable and I don't want to make something like switching of name and returning by hands new object type. Is it possible in c++ to do that automatically anyway? p.s. usage should looks like: dynamic_cast<Der1>(objectByType("Der1")); I need pure c++ code (crossplatform). Using boost is permissible.

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• .NET's double.NaN - how does this counterintuitive feature work?

  - by GeReV

  I stumbled upon the definition of double.NaN in code: public const double NaN = (double)0.0 / (double)0.0; This is done similarly in PositiveInfinity and NegativeInfinity. double.IsNaN (with removing a few #pragmas and comments) is defined as: [Pure] [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] public static bool IsNaN(double d) { if (d != d) { return true; } else { return false; } } This is, by far, the most counterintuitive thing I have ever seen in the .NET framework. How is 0.0 / 0.0 represented "behind the scenes"? How can division by 0 be possible in double, and why does NaN != NaN?

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• Parse and Break: why break cannot be used for getting out of "any" or "some" rule ?

  - by Rebol Tutorial

  Let say I have to parse a hierarchical set of tags <tag> <subtag1 attr1=value1 attr2=value2> <subtag1 attr1=value1 attr2=value2> <subtag1 attr1=value1 attr2=value2> </tag> Why can't I use break inside some or any to get out of a level hierarchy ? This would allow to do that kind of parsing instead of having a headache to do so ? I'm asking this because I read here http://www.codeconscious.com/rebol/parse-tutorial.html it would create an infinite loop This case produces an infinite loop. Because the BREAK is within a sub-rule of the rule that SOME is processing. The BREAK does not affect success/failure status or the input pointer - it just exits a rule early: rule-to-break: [(print "Break") break] == [(print "Break") break] parse "X" [some [rule-to-break] "X"] Break *Break* ... Break *Break*(escape)

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• How can I declare constant strings for use in both an unmanaged C++ dll and in a C# application?

  - by Surfbutler

  Curently I'm passing my const string values up from my C++ into my C# at startup via a callback, but I'm wondering if there's a way of defining them in a C++ header file that I can then also refer to in C#. I already do this with enums as they are easy. I include a file in both my C++ library project (via a .h file with a pragma once at the top), and my C# application (as a link): #if _NET public #endif enum ETestData { First, Second }; I know it sounds messy, but it works :) But...how can I do the same with string constants - I'm initially thinking the syntax is too different between the platforms, but maybe there's a way? Using clever syntax involving #if _NET, #defines etc? Using resource files? Using a C++/CLI library? Any ideas?

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• Initializing a array after declaration

  - by robUK

  Hello, gcc 4.4.3 c89 I have the following code as a sample of what I am trying to do. I don't know the actual size of the array, until I enter the function. However, I don't think I can set the array size after I have declared it. I need it global as some other functions will need to access the device names. Many thanks for any suggestions, /* global */ char *devices_names[]; void fill_devices(size_t num_devices) { devices_names[num_devices]; /* start filling */ }

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• Appending item to lists - python

  - by ariel

  I have a list lets say a=[[1,2],[3,4],[5,6]]. I want to add to each item in a the char 'a'. when I use a=[x.append('a') for x in a] it return [None,None,None]. But if I use a1=[x.append('a') for x in a] then it do someting odd. a and not a1 is [[1,2,a],[3,4,a],[5,6,a]]. I don't understand why the first return [None, None, None] nor why the second works on a.

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• Pass the current state of a function into another function in C/C++

  - by sand

  Is there a way to pass the current state of a function into another function in C/C++? I mean all the parameters and local variables by current state. For example: void funcA (int a, int b) { char c; int d, e; // Do something with the variables. // ... funcB(); // Do something more. } void funcB() { // funcB() should be able to access variables a,b,c,d & e // and any change in these variables reflect into funcA(). } The code is in bad shape if there is a need for funcB() kind of functions. But can it be achieved? This can help if someone is starting to re-factor a long method with multiple parameters.

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• Large amount of constants in Java

  - by Lars D

  I need to include about 1 MByte of data in a Java application, for very fast and easy access in the rest of the source code. My main background is not Java, so my initial idea was to convert the data directly to Java source code, defining 1MByte of constant arrays, classes (instead of C++ struct) etc., something like this: public final/immutable/const MyClass MyList[] = { { 23012, 22, "Hamburger"} , { 28375, 123, "Kieler"} }; However, it seems that Java does not support such constructs. Is this correct? If yes, what is the best solution to this problem?

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• haskell. words into binary numbers

  - by Katja

  I need to convert words into binary numbers. With a bit help of yours I got this blCo::String -> Integer blCo x = num2bin(lett2num x) blCo (x:xs) | x:xs = num2bin(lett2num x):blCo xs num2lett :: Int -> Char num2lett n | (n <= ord 'A') && (n <= ord 'Z') = chr(ord 'A'+ n - 1) | (n <= ord 'a') && (n <= ord 'Z') = chr(ord 'A'+ n - 1) num2bin :: Integer -> String num2bin n | n >= 0 = concatMap show (reverse ( n2b n)) | otherwise = error "num2bin: negative number" where n2b 0 = [] n2b n = n `mod` 2 : n2b (n `div` 2) he tells me a mistake.I dont undertsand it mistake: Couldn't match expected type `Char' against inferred type `String' In the first argument of `lett2num', namely `x' In the first argument of `num2bin', namely `(lett2num x)' In the expression: num2bin (lett2num x)

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• C++ Arrays of Structure access

  - by learningtolive

  Hi, I'm studying C++ from Schildt's book and don't quite understand what does he mean under third structure; Can somebody explain this - To access a specific structure within an array of structures, you must index the structure name. For example, to display the on_hand member of the third structure, you would write cout cout << invtry[2].on_hand; Some code: struct type{ char item[40]; double cost; double retail; int on_hand; int lead_time; }invtry[SIZE];

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• Function to register functions to be called if event invoked.

  - by zaidwaqi

  Hi, I have a Panel which contains 20 PictureBox controls. If a user clicks on any of the controls, I want a method within the Panel to be called. How do I do this? public class MyPanel : Panel { public MyPanel() { for(int i = 0; i < 20; i++) { Controls.Add(new PictureBox()); } } // DOESN'T WORK. // function to register functions to be called if the pictureboxes are clicked. public void RegisterFunction( <function pointer> func ) { foreach ( Control c in Controls ) { c.Click += new EventHandler( func ); } } } How do I implement RegisterFunction()? Also, if there are cool C# features that can make the code more elegant, please share. Thanks.

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• Preserve trailing whitespace Sybase

  - by AngryWhenHungry

  I have a big chunk of textual data which I split and write multiple rows of a varchar(255) column of a table. Sometimes, the last character happens to be a space. When I read back this row, the trailing space is chopped and I get only 254 characters. This messes up my data when I append the next row to the end of this one. My code sends the full 255 char (incl space) to the DB API. How can I check that the trailing space is actually written to the table? I am not in a position to rewrite/redesign legacy code. Is there any setting - either in the DB, DB interface, read/write calls etc - that I can use to preserve the trailing space?

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• Does the Internet make us less good programmers? [closed]

  - by stagas

  With all the information and code available nowadays on the Internet has that diminished our capability of remembering or learning stuff just because we know they're available somewhere out there, just a Google away or a StackOverflow question away? For example I find myself visiting php.net quite often to check the syntax of the same functions over and over again, not because my memory sucks, but I don't feel like keeping the information in me, since I know I'll find it again on the net. And about StackOverflow, isn't the process of figuring things out on your own supposed to improve your programming skills? If the answers are all just clicks away, do we actually learn something or just keep a pointer in our heads where to search for it again when we need it? Your thoughts are welcome. Hope it doesn't shut down as subjective or anything, the answers would be really interesting ;)

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• VS 2008, is there a way to search properties like the old vb6/EVB? CTRL+SHIFT?

  - by Davery

  I really miss the CTRL+SHIFT+CHAR searching of a property in VS 2008 that older IDE's had... typing CTRL+SHIFT+T got you to "tabindex" then Tag when pressed again. They dropped it in VS 2002 I believe, and the closest I could find to restoring any functionality like it was acorn's property window filter, which isn't exactly functional. Does anyone know of a way to get this functionality back? I hate having to browse through 30-40 properties in design mode, when a CTRL+SHIFT+T would get me right to text. Thanks!

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• Object reference not set to an instance of an object

  - by Ste

  I have this function that create runtime textbox: int i = 0; private TextBox[] addressBox = new TextBox[100]; private void appendNewTab() { addressBox[i] = new TextBox(); addressBox[i].KeyPress += new KeyPressEventHandler(this.addressBox_KeyPress); i++; } void addressBox_KeyPress(object sender, KeyPressEventArgs e) { if (e.KeyChar == (char)13) { MessageBox.Show(addressBox[i].Text); } } but i have Object reference not set to an instance of an object here MessageBox.Show(addressBox[i].Text); any suggestion?

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• Replacing the end of the line by SED in makefile

  - by Masi

  How can you append to the end of a line by SED controlled by makefile? I run paste -d" " t.tex tE.tex | sed 's@$@XXX@' > tM.tex where the problem is in the use of the mark $ for the end of the line. I get #paste -d" " t.tex tE.tex | sed -e s/" "/\\\&/g | sed -r "s/XXX/" > tM.tex sed: -e expression #1, char 10: unterminated `s' command make: *** [all] Error 1 I have the command just after the "all:" tag in my makefile which contains only the two lines. The parameters -n and -e do not help here. The command works as expected run when it is run directly in terminal.

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• Memory allocated with malloc does not persist outside function scope?

  - by PM

  Hi, I'm a bit new to C's malloc function, but from what I know it should store the value in the heap, so you can reference it with a pointer from outside the original scope. I created a test program that is supposed to do this but I keep getting the value 0, after running the program. What am I doing wrong? int f1(int * b) { b = malloc(sizeof(int)); *b = 5; } int main() { int * a; f1(a); printf("%d\n", a); return 0; }

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• C++ Vector of pointers

  - by xbonez

  For my latest CS homework, I am required to create a class called Movie which holds title, director, year, rating, actors etc. Then, I am required to read a file which contains a list of this info and store it in a vector of pointers to Movies. I am not sure what the last line means. Does it mean, I read the file, create multiple Movie objects. Then make a vector of pointers where each element (pointer) points to one of those Movie objects? Do I just make two vectors - one of pointers and one of Movies and make a one-to-one mapping of the two vectors?

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