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  • C++ Typing and OOP child classes

    - by Zack
    I'm a bit confused: If I have a base class A, and a class B which extends A, can a variable of the type A hold a value of the type B and vice versa? If yes, why? Aren't they completely different even if B is derived from A? How about type-safety? If this is possible, what things do I have to mind when taking use of this? How would this work out in terms of performance? Note: Sorry if I asked too many questions, just ignore them and just look out for those "marked" with the list decoration dot :) Also, this is not my homework. I'm a hobby programmer and have skills in scripting languages with OOP, yet I'm relatively new to OOP typing in C++.

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  • how to get the parent dir location using python..

    - by zjm1126
    this code is get the templates/blog1/page.html in b.py: path = os.path.join(os.path.dirname(__file__), os.path.join('templates', 'blog1/page.html')) but i want to get the parent dir location: a |---b.py |---templates |--------blog1 |-------page.html and how to get the a location thanks

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  • Execute a method less times possible - PHP

    - by serhio
    I have a site in multiple languages. I have a method that returns me the today currencies in a array. I display that currencies in a table then. // --- en/index.php <?php include_once "../exchangeRates.php"; $currencies = ReadExchangeRates(); // --- fr/index.php <?php include_once "../exchangeRates.php"; $currencies = ReadExchangeRates(); ... // somewhere in the page <td><?php echo $currencies["eur"]["today"]; ?></td> So, every time I load, en/ or fr/ or other language, I request the exchange rates from a external site. Can I optimize this behavior (reading once per day or session)? maybe to store a global variable and check the update date?

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  • Where to start to learn Android?

    - by Tuffy G
    I want to start making a program for a local charity on the Android platform. Where can go I for resources and tutorials to learn? I'm very new at this, so would like something simple that can be followed by someone with minimal technical knowledge.

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  • Java: Inputting text from a file using split

    - by 00PS
    I am inputting an adjacency list for a graph. There are three columns of data (vertex, destination, edge) separated by a single space. Here is my implementation so far: FileStream in = new FileStream("input1.txt"); Scanner s = new Scanner(in); String buffer; String [] line = null; while (s.hasNext()) { buffer = s.nextLine(); line = buffer.split("\\s+"); g.add(line[0]); System.out.println("Added vertex " + line[0] + "."); g.addEdge(line[0], line[1], Integer.parseInt(line[2])); System.out.println("Added edge from " + line[0] + " to " + line[1] + " with a weight of " + Integer.parseInt(line[2]) + "."); } System.out.println("Size of graph = " + g.size()); Here is the output: Added vertex a. Added edge from a to b with a weight of 9. Exception in thread "main" java.lang.NullPointerException at structure5.GraphListDirected.addEdge(GraphListDirected.java:93) at Driver.main(Driver.java:28) I was under the impression that line = buffer.split("\\s+"); would return a 2 dimensional array of Strings to the variable line. It seemed to work the first time but not the second. Any thoughts? I would also like some feedback on my implementation of this problem. Is there a better way? Anything to help out a novice! :)

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  • Python: combine two neighbor list components

    - by kame
    When i use this code I get elements wich containing one number or letter. How to combine two neighbors? data = '4D41544C414220352E30204D41542D66696C652C20506C6174666F726D3A20504357494E2C2043726561746564206F6E3A20576564204D61792030352031363A31393A3337203230313020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020200001494D0F00000026000000789CE36360607000623620E680D220C00AE53343312310BA00692620E604F351010025BE00C8' data2 = list(data) print data2

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  • SQL-wrappers (activerecord) to recommened for python?

    - by Horace Ho
    is there an activerecord (any similar SQL-wrapper) for python? which is good for: used in a server-side python script light-weight supports MySQL what I need to do: insert (filename, file size, file md5, the file itself) into (string, int, string, BLOB) columns if the same file (checksum + filename) does not exist in db thx

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  • Retrieving Oracle Cursor with JDBC

    - by BeginnerAmongBeginners
    I have been experiencing some frustrations trying to make a simple Oracle cursor retrieval procedure work with JDBC. I keep on getting an error of "[Oracle][ODBC][Ora]ORA-06553: PLS-306: wrong number or types of arguments in call to 'GETNAME'", but I cannot figure out what I am doing wrong. Here is my code in Java: CallableStatement stmt = connection.prepareCall("call getName(?)"); stmt.registerOutputParameter(1, OracleTypes.CURSOR); stmt.execute(); stmt.close(); con.close(); Here is my procedure in Oracle: CREATE OR REPLACE PROCEDURE getName(cur out SYS_REFCURSOR) IS BEGIN OPEN cur FOR SELECT name FROM customer; END; Thanks in advance. By the way, I am working with Oracle 10.2.0.

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  • Parse error in PHP login form

    - by user225269
    I'm trying to have a login form in php. But my current code doesnt work. Here is the form: <form name="form1" method="post" action="loginverify.php"> <td><font size="3">Username:</td> <td></td> <td><input type="text" name="uname" value="" maxlength="15"/><br/></td> <td><font size="3">Password:</td> <td></td> <td><input type="text" name="pword" value="" maxlength="15"/><br/></td> <tr> <td>&nbsp;</td> <td>&nbsp;</td> <td><input type="submit" name="Submit" value="Login" /></td> </form> And the verify.php <?php session_start(); ?> <?php $host="localhost"; $username="root"; $password="nitoryolai123$%^"; $db_name="login"; $tbl="users"; $connection=mysql_connect($host, $username, $password) or die("cannot connect"); mysql_select_db($db_name, $connection) or die("cannot select db"); $user=$_POST['uname'] $pass=$_POST['pword'] $sql="SELECT Username, Password from users where Username='$user' and Password='$pass'"; $result=mysql_query[$sql]; $count=mysql_num_rows($result); if($count==1){ $SESSION['Username']=$user; echo"<a href='searchmain.php'> CONTINUE</a>"; } else{ echo"wrong username or password"; echo"<a href='loginform.php'>Back</a>"; } ?> Is there something wrong with my code. I get this parse error at line 15, which is this: $pass=$_POST['pword'] But when I try to remove it.It goes to line 16 or line 17 again. What do I do

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  • Efficient way to build a MySQL update query in Python

    - by ensnare
    I have a class variable called attributes which lists the instance variables I want to update in a database: attributes = ['id', 'first_name', 'last_name', 'name', 'name_url', 'email', 'password', 'password_salt', 'picture_id'] Each of the class attributes are updated upon instantiation. I would like to loop through each of the attributes and build a MySQL update query in the form of: UPDATE members SET id = self._id, first_name = self._first name ... Thanks.

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  • On Developing Web Services with Global State

    - by user74418
    I'm new to web programming. I'm more experienced and comfortable with client-side code. Recently, I've been dabbling in web programming through Python's Google App Engine. I ran into some difficulty while trying to write some simple apps for the purposes of learning, mainly involving how to maintain some kind of consistent universally-accessible state for the application. I tried to write a simple queueing management system, the kind you would expect to be used in a small clinic, or at a cafeteria. Typically, this is done with hardware. You take a number from a ticketing machine, and when your number is displayed or called you approach the counter for service. Alternatively, you could be given a small pager, which will beep or vibrate when it is your turn to receive service. The former is somewhat better in that you have an idea of how many people are still ahead of you in the queue. In this situation, the global state is the last number in queue, which needs to be updated whenever a request is made to the server. I'm not sure how to best to store and maintain this value in a GAE context. The solution I thought of was to keep the value in the Datastore, attempt to query it during a ticket request, update the value, and then re-store it with put. My problem is that I haven't figured out how to lock the resource so that other requests do not check the value while it is in the middle of being updated. I am concerned that I may end up ticket requests that have the same queue number. Also, the whole solution feels awkward to me. I was wondering if there was a more natural way to accomplish this without having to go through the Datastore. Can anyone with more experience in this domain provide some advice on how to approach the design of the above application?

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  • Standard library function in R for finding the mode?

    - by Nick
    In statistical language R, mean() and median() are standard functions which do what you'd expect. mode() tells you the internal storage mode of the R object, not the value that occurs the most in its argument. But surely there is a standard library function that implements mode for a vector (or list).

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  • How to pass objects to functions in C++?

    - by Rakesh K
    I am new to C++ programming, but I have experience in Java. I need guidance on how to pass objects to functions in C++. Do I need to pass pointers, references, or non-pointer and non-reference values? I remember in Java there are no such issues since we pass just the variable that holds reference to the objects. It would be great if you could also explain where to use each of those options.

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  • How to push further as a programmer?

    - by MaXX
    For the last, hmm, 6 months I've been reading into Programming in C, I got myself K&Rv2, BEEJ's socket guide, Expert C programming, Linux Systems Programming, the ISO/IEC 9899:1999 specification (real, and not draft). After receiving them from Amazon, I got Linux installed, and got to it. I'm done with K&R, about halfway through Expert C Programming, but still feel weak as a programmer, I'm sure it takes much more than 6 months of reading to become truly skilled, but my question is this: I've done all the exercises in K&Rv2 (in chapter 1) and some in other chapters, most of which are generally really boring. How do I lift my skills, and become truly great? I've invested money, time and a general lifestyle for something I truly desire, but I'm not sure how exactly to achieve it. Could someone explain to me, perhaps if I need to continuously code, what exactly I'm to code? I'm pretty sure, coding up hello world programs isn't going to teach me any more than I already know about anything. A friend of mine said "read" (with emphasis on read) a man page a day, but reading is all I do, I want to do, but I'm not sure what! I'm interested in security, but I'm not sure as a novice what to code that would be considered enough. Ah, I hope you don't delete this paste :) Thanks

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  • Am I doing something wrong here (references in C++)?

    - by m4design
    I've been playing around with references (I'm still having issues in this regard). 1- I would like to know if this is an acceptable code: int & foo(int &y) { return y; // is this wrong? } int main() { int x = 0; cout << foo(x) << endl; foo(x) = 9; // is this wrong? cout << x << endl; return 0; } 2- Also this is from an exam sample: Week & Week::highestSalesWeek(Week aYear[52]) { Week max = aYear[0]; for(int i = 1; i < 52; i++) { if (aYear[i].getSales() > max.getSales()) max = aYear[i]; } return max; } It asks about the mistake in this code, also how to fix it. My guess is that it return a local reference. The fix is: Week & max = aYear[0]; Is this correct/enough?

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  • Using PHP to populate a <select></select> ?

    - by Flins
    <select name="select"> </select> I want to populate the above tag with values from database. I have written php code up to this. while($row=mysql_fetch_array($result)) { } $row is fetching fetching correct values.. how to add it to the <select> please help... Am new to programming

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  • Is there an algorithm for finding an item that matches certain properties, like a 20 questions game?

    - by lala
    A question about 20 questions games was asked here: However, if I'm understanding it correctly, the answers seem to assume that each question will go down a hierarchal branching tree. A binary tree should work if the game went like this: Is it an animal? Yes. Is it a mammal? Yes. Is it a feline? Yes. Because feline is an example of a mammal and mammal is an example of an animal. But what if the questions go like this? Is it a mammal? Yes. Is it a predator? Yes. Does it have a long nose? No. You can't branch down a tree with those kinds of questions, because there are plenty of predators that aren't mammals. So you can't have your program just narrow it down to mammal and have predators be a subset of mammals. So is there a way to use a binary search tree that I'm not understanding or is there a different algorithm for this problem?

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  • How to make simple mathematical operations and displaying the result in a textbox

    - by Audel
    Hi, I know is a rather simple question but I just can't find an appropriate example in google or anywhere. I've got this piece int numberOfPlays = int.Parse(textBox2.Text); numberOfPlays = (numberOfPlays++); textBox2.Text = (numberOfPlays.ToString()); MessageBox.Show(numberOfPlays.ToString()); So basically what I want to do is to get the value of the textBox2, make it an integer and then add 1 to it. I can't think of any more details right now, so if i'm not clear enough please ask Thanks in advance

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  • how to delete all files in a folder, but not the folder itself?

    - by Frost Li
    I try to delete all files including subdirectories in a folder: NSFileManager *deleteMgr = [NSFileManager defaultManager]; NSString *path = @"~/test/"; [deleteMgr removeItemAtPath:path error:&error]; And it deletes everything including the folder itself. But what I expect is an empty folder. Could anyone please help me what did I do wrong? Really thanks your help! :)

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  • How to merge code on svn

    - by London
    I'm using subeclipse plugin for eclipse for SVN. My project looks like this : ProjectName\ - branches - special_ - tags - trunk I have currently checked out project from special_ and I've modified and added one class, how can I merge the code which I updated/added to trunk ? I'll take anything into consideration

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  • Dynamically creating/inserting into an associative array in PHP

    - by emil.mp
    I'm trying to build an associative array in PHP dynamically, and not quite getting my strategy right. Basically, I want to insert a value at a certain depth in the array structure, for instance: $array['first']['second']['third'] = $val; Now, the thing is, I'm not sure if that depth is available, and if it isn't, I want to create the keys (and arrays) for each level, and finally insert the value at the correct level. Since I'm doing this quite a lot in my code, I grew tired of doing a whole bunch of "array_key_exists", so I wanted to do a function that builds the array for me, given a list of the level keys. Any help on a good strategy for this is appreciated. I'm sure there is a pretty simple way, I'm just not getting it...

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