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  • Is Prolog the best language to solve this kind of problem?

    - by Milan Babuškov
    I have this problem containing some inequations and requirement to minimize a value. After doing some research on the Internet, I came to conclusion that using Prolog might be the easiest way to solve it. However, I never used Prolog before, and I would hate to waste my time learning it just to discover that it is not the right tool for this job. Please, if you know Prolog, take a look at this problem and tell me if Prolog is the right one. Or, if you know of some other language that is really suited for this. a + b + c >= 100 d + e + f >= 50 g + h >= 30 if (8b + 2e + 7h > 620) then y = 0.8 else y = 1.0 if (d > 35) then x = 0.9 else x = 1.0 5xa + 8yb + 5c + 3xd + 2ye + 2f + 6xg + 7yh = w. I need to find the values for a, b, c, d, e, f, g and h that minimize w. I'm not really asking for code, although I'd be grateful for some hint how to tackle this if Prolog is really good for it. Thanks.

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  • Error in django using Apache & mod_wsgi

    - by Ignacio
    Hey, I've been doing some changes to my django develpment env, as some of you suggested. So far I've managed to configure and run it successfully with postgres. Now I'm trying to run the app using apache2 and mod_wsgi, but I ran into this little problem after I followed the guidelines from the django docs. When I access localhost/myapp/tasks this error raises: Request Method: GET Request URL: http://localhost/myapp/tasks/ Exception Type: TemplateSyntaxError Exception Value: Caught an exception while rendering: argument 1 must be a string or unicode object Original Traceback (most recent call last): File "/usr/local/lib/python2.6/dist-packages/django/template/debug.py", line 71, in render_node result = node.render(context) File "/usr/local/lib/python2.6/dist-packages/django/template/defaulttags.py", line 126, in render len_values = len(values) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 81, in __len__ self._result_cache = list(self.iterator()) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 238, in iterator for row in self.query.results_iter(): File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/query.py", line 287, in results_iter for rows in self.execute_sql(MULTI): File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/query.py", line 2369, in execute_sql cursor.execute(sql, params) File "/usr/local/lib/python2.6/dist-packages/django/db/backends/util.py", line 19, in execute return self.cursor.execute(sql, params) TypeError: argument 1 must be a string or unicode object ... ... ... And then it highlights a {% for t in tasks %} template tag, like the source of the problem is there, but it worked fine on the built-in server. The view associated with that page is really simple, just fetch all Task objects. And the template just displays them on a table. Also, some pages get rendered ok. Don't want to fill this Question with code, so if you need some more info I'd be glad to provide it. Thanks

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  • What rules govern the copying of variables in Javascript closures?

    - by int3
    I'd just like to check my understanding of variable copying in Javascript. From what I gather, variables are passed/assigned by reference unless you explicitly tell them to create a copy with the new operator. But I'm a little uncertain when it comes to using closures. Say I have the following code: var myArray = [1, 5, 10, 15, 20]; var fnlist = []; for (var i in myArray) { var data = myArray[i]; fnlist.push(function() { var x = data; console.log(x); }); } fnlist[2](); // returns 20 I gather that this is because fnlist[2] only looks up the value of data at the point where it is invoked. So I tried an alternative tack: var myArray = [1, 5, 10, 15, 20]; var fnlist = []; for (var i in myArray) { var data = myArray[i]; fnlist.push(function() { var x = data; return function() { console.log(x); } }()); } fnlist[2](); // returns 10 So now it returns the 'correct' value. Am I right to say that it works because a function resolves all variable references to their 'constant' values when it is invoked? Or is there a better way to explain it? Any explanations / links to explanations regarding this referencing / copying business would be appreciated as well. Thanks!

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  • How to find sum of node's value for given depth in binary tree?

    - by masato-san
    I've been scratching my head for several hours for this... problem: Binary Tree (0) depth 0 / \ 10 20 depth 1 / \ / \ 30 40 50 60 depth 2 I am trying to write a function that takes depth as argument and return the sum of values of nodes of the given depth. For instance, if I pass 2, it should return 180 (i.e. 30+40+50+60) I decided to use breath first search and when I find the node with desired depth, sum up the value, but I just can't figure out how to find out the way which node is in what depth. But with this approach I feel like going to totally wrong direction. function level_order($root, $targetDepth) { $q = new Queue(); $q->enqueue($root); while(!$q->isEmpty) { //how to determin the depth of the node??? $node = $q->dequeue(); if($currentDepth == $targetDepth) { $sum = $node->value; } if($node->left != null) { $q->enqueue($node->left); } if($node->right != null) { $q->enqueue($node->right); } //need to reset this somehow $currentDepth ++; } }

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  • Is False == 0 and True == 1 in Python an implementation detail or guaranteed by the language?

    - by EOL
    Is it guaranteed that False == 0 and True == 1, in Python? For instance, is it in any way guaranteed that the following code will always produce the same results, whatever the version of Python (existing and in the foreseeable future)? 0 == False # True 1 == True # True ['zero', 'one'][False] # is 'zero' Any reference to the official documentation would be much appreciated! Other comments would be appreciated too… :) Edit: As noted in many answers, bool inherits from int. The question can therefore be recast as: "Is this an implementation detail that might change in the future, or does the documentation officially say that programmers can rely on booleans inheriting from integers?". This question is relevant for writing robust code that won't fail because of implementation details! Edit 2: The original question is still open, I believe (even though I accepted what I thought was the closest answer): even though Python 3 officially recognizes booleans as integers, I have not yet seen any official integer values for False and True… It therefore looks to me like it is best to stay clear from the assumption that False==0 and True==1.

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  • "pseudo-atomic" operations in C++

    - by dan
    So I'm aware that nothing is atomic in C++. But I'm trying to figure out if there are any "pseudo-atomic" assumptions I can make. The reason is that I want to avoid using mutexes in some simple situations where I only need very weak guarantees. 1) Suppose I have globally defined volatile bool b, which initially I set true. Then I launch a thread which executes a loop while(b) doSomething(); Meanwhile, in another thread, I execute b=true. Can I assume that the first thread will continue to execute? In other words, if b starts out as true, and the first thread checks the value of b at the same time as the second thread assigns b=true, can I assume that the first thread will read the value of b as true? Or is it possible that at some intermediate point of the assignment b=true, the value of b might be read as false? 2) Now suppose that b is initially false. Then the first thread executes bool b1=b; bool b2=b; if(b1 && !b2) bad(); while the second thread executes b=true. Can I assume that bad() never gets called? 3) What about an int or other builtin types: suppose I have volatile int i, which is initially (say) 7, and then I assign i=7. Can I assume that, at any time during this operation, from any thread, the value of i will be equal to 7? 4) I have volatile int i=7, and then I execute i++ from some thread, and all other threads only read the value of i. Can I assume that i never has any value, in any thread, except for either 7 or 8? 5) I have volatile int i, from one thread I execute i=7, and from another I execute i=8. Afterwards, is i guaranteed to be either 7 or 8 (or whatever two values I have chosen to assign)?

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  • SQL code to display counts() of value retrieved from another column

    - by Doctor Trout
    I have three tables (these are the relevant columns): Table1 bookingid, person, role Table2 bookingid, projectid Table3 projectid, project, numberofrole1, numberofrole2 Table1.role can take two values: "role1" or "role2". What I want to do is to show which projects don't have the correct number of roles in Table1. The number of roles there there should be for each role is in Table3. For example, if Table1 contains these three rows: bookingid, person, role 7, Tim, role1 7, Bob, role1, 7, Charles, role2 and Table2 bookingid, projectid 7, 1 and Table3 projectid, project, numberofrole1, numberofrole2 1, Test1, 2, 2 I would like the results to show that there are not the correct number of role2s for project Test1. To be honest, something like this is a bit beyond my ability, so I'm open to suggestions on the best way to do this. I'm using sqlite and php (it's only a small project). I suppose I could do something with the php at the end once I've got my results, but I wondered if there was a better way to do it with sqlite. I started by doing something like this: SELECT project, COUNT(numberofrole1) as "Role" FROM Table1 JOIN Table2 USING (projectid) JOIN Table3 USING (bookingid) WHERE role="role1" GROUP BY project But I can't work out how to compare the value returned as "Role" with the value got from numberofrole1 Any help is gratefully received.

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  • Visual studio 2008 unit test keeps failing

    - by Gerbrand
    I've create a method that calculates the harmonic mean based on a list of doubles. But when I'm running the test it keeps failing even thou the output result are the same. My harmonic mean method: public static double GetHarmonicMean(List<double> parameters) { var cumReciprocal = 0.0d; var countN = parameters.Count; foreach( var param in parameters) { cumReciprocal += 1.0d/param; } return 1.0d/(cumReciprocal/countN); } My test method: [TestMethod()] public void GetHarmonicMeanTest() { var parameters = new List<double> { 1.5d, 2.3d, 2.9d, 1.9d, 5.6d }; const double expected = 2.32432293165495; var actual = OwnFunctions.GetHarmonicMean(parameters); Assert.AreEqual(expected, actual); } After running the test the following message is showing: Assert.AreEqual failed. Expected:<2.32432293165495. Actual:<2.32432293165495. For me that are both the same values. Can somebody explain this? Or am I doing something wrong?

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  • XCode Obj-C: Make new NSArray from one key each out of an Array of Dictionaries

    - by user323772
    This actually could be a multipart question. But here's the first part ... I have an array (actually in a plist) of dictionaries. Each dictionary has 3 keys in it: (title), (points), and (description). I am trying to make a NEW array with the values of the key "title" from each dictionary in that first array. Let me explain WHY I am doing this and maybe that will provide a better all around explanation. I am trying to let people pick from a pre-determined list. Heck, if this was a web page it would be very simple since all I really care about are the "points" and the "Title". On a web site I could simply do a drop down combo-box with the "points" being the value and the title being the text for each row. But this is not a web page. So what I am trying to do here is pop out a modal picker when they click the text field. The modal picker shows the alphabetical ordered "titles" from our new array. And whichever one they select, it closes the modal view and assigns that "title" text to the UITextField which cannot be edited by the user. I have some code to get my modal picker to pop out. But I need to feed it an array of just the "titles" of each dictionary in my real array. Thanks in advance (and yes I am a newbie)

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  • Efficient batch SQL query execution on Android, for upgrade database.

    - by Pentium10
    As we Android developers know, the SQLiteDatabase execSQL method can execute only one statement. The doc says: Execute a single SQL statement that is not a query. For example, CREATE TABLE, DELETE, INSERT, etc. Multiple statements separated by ;s are not supported. I have to load in a batch of records, 1000 and counting. How do I insert these efficiently? And what's the easiest way to deliver these SQLs with your apk? I mention, there is already a system database and I will run this on the onUpdate event. I have this code so far: List<String[]> li = new ArrayList<String[]>(); li.add(new String[] { "-1", "Stop", "0" }); li.add(new String[] { "0", "Start", "0" }); /* the rest of the assign */ try { for (String[] elem : li) { getDb().execSQL( "INSERT INTO " + TABLENAME + " (" + _ID + "," + NAME + "," + PARSE_ORDER + ") VALUES (?,?,?)", elem); } } catch (Exception e) { e.printStackTrace(); }

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  • What is the meaning of @ModelAttribute annotation at method argument level?

    - by beemaster
    Spring 3 reference teaches us: When you place it on a method parameter, @ModelAttribute maps a model attribute to the specific, annotated method parameter I don't understand this magic spell, because i sure that model object's alias (key value if using ModelMap as return type) passed to the View after executing of the request handler method. Therefore when request handler method executes the model object's name can't be mapped to the method parameter. To solve this contradiction i went to stackoverflow and found this detailed example. The author of example said: // The "personAttribute" model has been passed to the controller from the JSP It seems, he is charmed by Spring reference... To dispel the charms i deployed his sample app in my environment and cruelly cut @ModelAttribute annotation from method MainController.saveEdit. As result the application works without any changes! So i conclude: the @ModelAttribute annotation is not needed to pass web form's field values to the argument's fields. Then i stuck to the question: what is the mean of @ModelAttribute annotation? If the only mean is to set alias for model object in View, then why this way better than explicitly adding of object to ModelMap?

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  • Need help optimizing this Django aggregate query

    - by Chris Lawlor
    I have the following model class Plugin(models.Model): name = models.CharField(max_length=50) # more fields which represents a plugin that can be downloaded from my site. To track downloads, I have class Download(models.Model): plugin = models.ForiegnKey(Plugin) timestamp = models.DateTimeField(auto_now=True) So to build a view showing plugins sorted by downloads, I have the following query: # pbd is plugins by download - commented here to prevent scrolling pbd = Plugin.objects.annotate(dl_total=Count('download')).order_by('-dl_total') Which works, but is very slow. With only 1,000 plugins, the avg. response is 3.6 - 3.9 seconds (devserver with local PostgreSQL db), where a similar view with a much simpler query (sorting by plugin release date) takes 160 ms or so. I'm looking for suggestions on how to optimize this query. I'd really prefer that the query return Plugin objects (as opposed to using values) since I'm sharing the same template for the other views (Plugins by rating, Plugins by release date, etc.), so the template is expecting Plugin objects - plus I'm not sure how I would get things like the absolute_url without a reference to the plugin object. Or, is my whole approach doomed to failure? Is there a better way to track downloads? I ultimately want to provide users some nice download statistics for the plugins they've uploaded - like downloads per day/week/month. Will I have to calculate and cache Downloads at some point? EDIT: In my test dataset, there are somewhere between 10-20 Download instances per Plugin - in production I expect this number would be much higher for many of the plugins.

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  • Will these security functions be enough? (PHP)

    - by ggfan
    I am trying to secure my site so I don't have sql injections and xss scripting. Here's my code. //here's the from, for brevity, i just show a field for users to put firstname <form> <label for="first_name" class="styled">First Name:</label> <input type="text" id="first_name" name="first_name" value="<?php if (!empty($first_name)) echo $first_name; ?>" /><br /> //submit button etc </form> if (isset($_POST['submit'])) { //gets rid of extra whitesapce and escapes $first_name = mysqli_real_escape_string($dbc, trim($_POST['first_name'])); //check if $first_name is a string if(!is_string($first_name) { echo "not string"; } //then insert into the database. ....... } mysqli_real_espace_string: I know that this func escapes certain letters like \n \r, so when the data gets inputted into the dbc, it would have '\' next to all the escaped letters? --Will this script be enough to prevent most sql injections? just escaping and checking if the data is a string. For integers values(like users putting in prices), i just: is_numeric(). --How should I use htmlspecialchars? Should I use it only when echoing and displaying user data? Or should I also use this too when inputting data to a dbc? --When should I use strip_tags() or htmlspecialchars? SOO with all these function... if (isset($_POST['submit'])) { //gets rid of extra whitesapce and escapes $first_name = mysqli_real_escape_string($dbc, trim($_POST['first_name'])); //check if $first_name is a string if(!is_string($first_name) { echo "not string"; } //gets rid of any <,>,& htmlspecialchars($first_name); //strips any tags with the first name strip_tags($first_name) //then insert into the database. ....... } Which funcs should I use for sql injections and which ones should I use for xss?

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  • How can I use Perl to determine whether the contents of two files are identical?

    - by Zaid
    This question comes from a need to ensure that changes I've made to code doesn't affect the values it outputs to text file. Ideally, I'd roll a sub to take in two filenames and return 1or return 0 depending on whether the contents are identical or not, whitespaces and all. Given that text-processing is Perl's forté, it should be quite easy to compare two files and determine whether they are identical or not (code below untested). use strict; use warnings; sub files_match { my ( $fileA, $fileB ) = @_; open my $file1, '<', $fileA; open my $file2, '<', $fileB; while (my $lineA = <$file1>) { next if $lineA eq <$file2>; return 0 and last; } return 1; } The only way I can think of (sans CPAN modules) is to open the two files in question, and read them in line-by-line until a difference is found. If no difference is found, the files must be identical. But this approach is limited and clumsy. What if the total lines differ in the two files? Should I open and close to determine line count, then re-open to scan the texts? Yuck. I don't see anything in perlfaq5 relating to this. I want to stay away from modules unless they come with the core Perl 5.6.1 distribution.

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  • Error in value of default parameter [Bug in Visual C++ 2008?]

    - by HellBoy
    I am facing following issue while trying to use template in my code I have some C++ code which i call from C functions. Problem is I am getting different values in the following code for statement 1 and 2. Type id : unsigned int statement 1 : 4 statement 2 : 1 C++ Code : template <typename T> void func(T* value, unsigned int len = sizeof(T)) { cout << "Type id : " << typeid(T).name() << endl; cout << "statement 1 " << sizeof(T) << endl; cout << "statement 2 " << len << endl; } template <typename T> void func1(T data) { T val = data; func(&val); } C Code : void test(void *ptr, unsigned int len) { switch(len) { case 1: func1(*(static_cast<uint32_t *>(ptr)) break; } } This happens only on windows. On Linux it works fine.

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  • Multiple Foreign keys to a single table and single key pointing to more than one table

    - by user1216775
    I need some suggestions from the database design experts here. I have around six foreign keys into a single table (defect) which all point to primary key in user table. It is like: defect (.....,assigned_to,created_by,updated_by,closed_by...) If I want to get information about the defect I can make six joins. Do we have any better way to do it? Another one is I have a states table which can store one of the user-defined set of values. I have defect table and task table and I want both of these tables to share the common state table (New, In Progress etc.). So I created: task (.....,state_id,type_id,.....) defect(.....,state_id,type_id,...) state(state_id,state_name,...) importance(imp_id,imp_name,...) There are many such common attributes along with state like importance(normal, urgent etc), priority etc. And for all of them I want to use same table. I am keeping one flag in each of the tables to differentiate task and defect. What is the best solution in such a case? If somebody is using this application in health domain, they would like to assign different types, states, importances for their defect or tasks. Moreover when a user selects any project I want to display all the types,states etc under configuration parameters section.

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  • Declaration of struct variables in other class when obtained by getters

    - by liaK
    Hi, I am using Qt 4.5 so do C++. I have a class like this class CClass1 { private: struct stModelDetails { QString name; QString code; ..... // only variables and no functions over here }; QList<stModelDetails> m_ModelDetailsList; public: QList<stModelDetails> getModelDetailsList(); ... }; In this I have functions that will populate the m_ModelDetailsList; I have another class say CClassStructureUsage, where I will call the getModelDetailsList() function. Now my need is that I have to traverse the QList and obtain the name, code from each of the stModelDetails. Now the problem is even the CClass1's header file is included it is not able to identify the type of stModelDetails in CClassStructureUsage. When I get the structure list by QList<stModelDetails> ModelList = obj->getModelInformationList(); it says stModelDetails : undeclared identifier. How I can able to fetch the values from the structure? Am I doing anything wrong over here?

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  • Is a python dictionary the best data structure to solve this problem?

    - by mikip
    Hi I have a number of processes running which are controlled by remote clients. A tcp server controls access to these processes, only one client per process. The processes are given an id number in the range of 0 - n-1. Were 'n' is the number of processes. I use a dictionary to map this id to the client sockets file descriptor. On startup I populate the dictionary with the ids as keys and socket fd of 'None' for the values, i.e no clients and all pocesses are available When a client connects, I map the id to the sockets fd. When a client disconnects I set the value for this id to None, i.e. process is available. So everytime a client connects I have to check each entry in the dictionary for a process which has a socket fd entry of None. If there are then the client is allowed to connect. This solution does not seem very elegant, are there other data structures which would be more suitable for solving this? Thanks

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  • Win conditions for a connect-4 like game

    - by FrozenWasteland
    I have an 5x10 array that is populated with random values 1-5. I want to be able to check when 3 numbers, either horizontally, or vertically, match. I can't figure out a way to do this without writing a ton of if statements. Here is the code for the randomly populated array int i; int rowincrement = 10; int row = 0; int col = 5; int board[10][5]; int randomnum = 5; int main(int argc, char * argv[]) { srand(time(NULL)); cout << "============\n"; while(row < rowincrement) { for(i = 0; i < 5; i++) { board[row][col] = rand()%5 + 1; cout << board[row][col] << " "; } cout << endl; cout << "============\n"; row++; } cout << endl; return 0; }

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  • Fill fields on a webpage

    - by MajuiF
    Hi everyone, I've already asked this question, but it's still too unclear to me, and it seems people haven't understood what I'm trying to do, so I'll try and be clearer. This website: https://www4.polymtl.ca/poly/poly.html is the website I want to fill. What I would like to be able to do, is modify the values of the "nip", "code", and "naissance" fields with text (for example, code being "majuif"). <input type=password name=code size=8 maxlength=8> <input type=password name=nip size=8 maxlength=8> <input type=password name=naissance size=8 maxlength=8> However, I don't know how to do that. And this is my problem. Should I write another HTML file - I don't know if the word "macro" can be used for that, but I'm pretty sure it can - and insert JavaScript in it? Please note that I'm not a professional in JavaScript or HTML, but I have basics, and still learning. Thanks, -Max.

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  • Holding variables in memory, C++

    - by b-gen-jack-o-neill
    Today something strange came to my mind. When I want to hold some string in C (C++) the old way, without using string header, I just create array and store that string into it. But, I read that any variable definition in C in local scope of function ends up in pushing these values onto the stack. So, the string is actually 2* bigger than needed. Because first, the push instructions are located in memory, but then when they are executed (pushed onto the stack) another "copy" of the string is created. First the push instructions, than the stack space is used for one string. So, why is it this way? Why doesn't compiler just add the string (or other variables) to the program instead of creating them once again when executed? Yes, I know you cannot just have some data inside program block, but it could just be attached to the end of the program, with some jump instruction before. And than, we would just point to these data? Because they are stored in RAM when the program is executed. Thanks.

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  • multiplying all elements in an array by an outside number?

    - by prodo
    I need to multiple all the values in an array by 3000 which in turn would create a new array that I will use to subtract from another array. I've tried to create a separate method that would do that for me but all I got back in the multiplied array was a bunch of numbers and symbols strangely? here is the code that I wrote public static void main(String[] args) { int numberOfTaxpayers = Integer.parseInt(JOptionPane.showInputDialog("Enter how many users you would like to calculate taxes for: "); int[] usernumChild = new int[numberOfTaxPayers]; for (int i = 0; i < usernumChild.length; i++) { usernumChild[i] = Integer.parseInt(JOptionPane.showInputDialog("Enter number of children for user "+ (i+1) +": ")); }//this for loop finds out the number of children per user so we can later multiply each input by 3000 to create an array that determine dependency exemption for each user int[] depndExemp = multiply(usernumChild, 3000);//this was the calling of the multiply method... somewhere here is the error!! }//end main method public static int[] multiply(int[] children, int number) { int array[] = new int[children.length]; for( int i = 0; i < children.length; i++) { children[i] = children[i] * number; }//end for return array; }//this is the method that I was shown in a previous post on how to create return an array in this the dependency exemption array but when I tested this by printing out the dependency array all I received were a jumble of wrong numbers.

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  • update record only works when there is no auto_increment

    - by every_answer_gets_a_point
    i am accessing a mysql table through an odbc connection in excel here is how i am updating the table: With rs .AddNew ' create a new record ' add values to each field in the record .Fields("datapath") = dpath .Fields("analysistime") = atime .Fields("reporttime") = rtime .Fields("lastcalib") = lcalib .Fields("analystname") = aname .Fields("reportname") = rname .Fields("batchstate") = "bstate" .Fields("instrument") = "NA" .Update ' stores the new record End With when the schema of the table is this, updating it works: create table batchinfo(datapath text,analysistime text,reporttime text,lastcalib text,analystname text, reportname text, batchstate text, instrument text); but when i have auto_increment in there it does not work: CREATE TABLE batchinfo ( rowid int(11) NOT NULL AUTO_INCREMENT, datapath text, analysistime text, reporttime text, lastcalib text, analystname text, reportname text, batchstate text, instrument text, PRIMARY KEY (rowid) ) ENGINE=InnoDB AUTO_INCREMENT=67 DEFAULT CHARSET=latin1 has anyone experienced a problem like this where updating does not work when there is an auto_increment field involved? connection string: Private Sub ConnectDB() Set oConn = New ADODB.Connection oConn.Open "DRIVER={MySQL ODBC 5.1 Driver};" & _ "SERVER=localhost;" & _ "DATABASE=employees;" & _ "USER=root;" & _ "PASSWORD=pas;" & _ "Option=3" End Sub also here's the rs.open: rs.Open "batchinfo", oConn, adOpenKeyset, adLockOptimistic, adCmdTable

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  • C# Function Inheritance--Use Child Class Vars with Base Class Function

    - by Sean O'Connor
    Good day, I have a fairly simple question to experienced C# programmers. Basically, I would like to have an abstract base class that contains a function that relies on the values of child classes. I have tried code similar to the following, but the compiler complains that SomeVariable is null when SomeFunction() attempts to use it. Base class: public abstract class BaseClass { protected virtual SomeType SomeVariable; public BaseClass() { this.SomeFunction(); } protected void SomeFunction() { //DO SOMETHING WITH SomeVariable } } A child class: public class ChildClass:BaseClass { protected override SomeType SomeVariable=SomeValue; } Now I would expect that when I do: ChildClass CC=new ChildClass(); A new instance of ChildClass should be made and CC would run its inherited SomeFunction using SomeValue. However, this is not what happens. The compiler complains that SomeVariable is null in BaseClass. Is what I want to do even possible in C#? I have used other managed languages that allow me to do such things, so I certain I am just making a simple mistake here. Any help is greatly appreciated, thank you.

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  • Difficulty Inserting from HTML form into MySQL (created in Workbench)

    - by Chaya Cooper
    I created a MySQL database in Workbench 5.2.35 for purposes of storing and using information submitted in html forms but I'm having difficulty inserting records from the html form. The relevant SQL script was saved as Demo2.sql, the schema is C2F, and the table is customer_info. I wasn't sure if that was the problem, so I tried replacing the database name (Demo2) with the schema name, but that didn't work either. My html file includes: form action="insert.php" method="post" The insert.php file states: ?php $con = mysql_connect("localhost","root","****"); if (!$con) { die('Could not connect: ' . mysql_error()); } mysql_select_db("Demo2", $con); $sql="INSERT INTO customer_info(fname, lname, user, password, reminder, answer) VALUES ('$_POST[fname]','$_POST[lname]','$_POST[user]','$_POST[password]','$_POST[reminder]','$_POST[answer]')"; if (!mysql_query($sql,$con)) { die('Error: ' . mysql_error()); } echo "1 record added"; mysql_close($con) ? I've also tried INSERT INTO c2f.customer_info(fname, lname, etc. and INSERT INTO 'c2f'.'customer_info'

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