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  • Problem with do construct in haskell

    - by Anonymous Coward
    Hello everyone I'm trying to learn Haskell and want to write a small program which prints the content of a file to the screen. When I load it into GHCi I get the following error: The last statement in a 'do' construct must be an expression I know this question has be asked already here: Haskell — “The last statement in a 'do' construct must be an expression”. Even though my code is very similar I still can't figure out the problem. If anyone could point out the problem to me I'd be very thankful. module Main (main) where import System.IO import System(getArgs) main :: IO() main = do args <- getArgs inh <- openFile $ ReadMode head args printFile inh hClose inh printFile :: Handle -> IO () printFile handle = do end <- hIsEOF handle if end then return () else do line <- hGetLine handle putStrLn line printFile handle

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  • Reallocating memory via "new" in C++

    - by BSchlinker
    Quick question regarding memory management in C++ If I do the following operation: pointer = new char [strlen(someinput_input)+1]; And then perform it again, with perhaps a different result being returned from strlen(someinput_input). Does this result in memory being left allocated from the previous "new" statement? IE, is each new statement receiving another block of HEAP memory from the OS, or is it simply reallocating? Assuming I do a final delete pointer[]; will that deallocate any and all memory that I ever allocated via new to that pointer? Thanks

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  • Enums With Default Throw Clause?

    - by Tom Tresansky
    I noticed the following in the Java Language spec in the section on enumerations here: link switch(this) { case PLUS: return x + y; case MINUS: return x - y; case TIMES: return x * y; case DIVIDE: return x / y; } throw new AssertionError("Unknown op: " + this); However, looking at the switch statement definition section, I didn't notice this particular syntax (the associated throw statement) anywhere. Can I use this sort of "default case is throw an exception" syntactic sugar outside of enum definitions? Does it have any special name? Is this considered a good/bad practice for short-cutting this behavior of "anything not in the list throws an exception"?

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  • C optimization breaks algorithm

    - by Halpo
    I am programming an algorithm that contains 4 nested for loops. The problem is at at each level a pointer is updated. The innermost loop only uses 1 of the pointers. The algorithm does a complicated count. When I include a debugging statement that logs the combination of the indexes and the results of the count I get the correct answer. When the debugging statement is omitted, the count is incorrect. The program is compiled with the -O3 option on gcc. Why would this happen?

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  • Use SQL query to populate property in nHibernate mapping file

    - by brainimus
    I have an object which contains a property that is the result of an SQL statement. How do I add the SQL statement to my nHibernate mapping file? Example Object: public class Library{ public int BookCount { get; set; } } Example Mapping File: <hibernate-mapping> <class name="Library" table="Libraries"> <property name="BookCount" type="int"> <- This is where I want the SQL query to populate the value. -> </class> </hibernate-mapping> Example SQL Query: SELECT COUNT(*) FROM BOOKS WHERE BOOKS.LIBRARY_ID = LIBRARIES.ID

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  • PHP / Zend Framework: Which object would handle a complex table join?

    - by Thomas
    I think one of the more difficult concepts to understand in the Zend Framework is how the Table Data Gateway pattern is supposed to handle multi-table joins. Most of the suggestions I've seen claim that you simply handle the joins using a $db-select()... Zend DB Select with multiple table joins Joining Tables With Zend Framework PHP Joining tables wthin a model in Zend Php Zend Framework Db Select Join table help Zend DB Select with multiple table joins My question is: Which object is best suited to handle this kind of multi-table select statement? I feel like putting it in the model would break the 1-1 Table Data Gateway pattern between the class and the db table. Yet putting it in the controller seems wrong because why would a controller handle a SQL statement? Anyway, I feel like ZF makes handling datasets from multiple tables more difficult than it needs to be. Any help you can provide is great... Thanks!

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  • How do I submit really big amounts of data to a form?

    - by William Calleja
    I have an HTML from that's posting a really big amount of data which is eventually being saved into an SQL Server 2005, the form is as follows: <form name="frmForm" method="post" action="saveData.aspx"> the target page takes the content of a control within the form and saves it to the database through a normal SQL insert statement. However only a portion of the data is being saved. The field in the database is an ntext. Should I use a different field? Or is something happening while I'm transferring from one page to another? Or even still there's something happening when I'm sending the really big SQL statement through c# in saveData.aspx?

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  • Python: How can I override one module in a package with a modified version that lives outside the pa

    - by zlovelady
    I would like to update one module in a python package with my own version of the module, with the following conditions: I want my updated module to live outside of the original package (either because I don't have access to the package source, or because I want to keep my local modifications in a separate repo, etc). I want import statements that refer to original package/module to resolve to my local module Here's an example of what I'd like to do using specifics from django, because that's where this problem has arisen for me: Say this is my project structure django/ ... the original, unadulterated django package ... local_django/ conf/ settings.py myproject/ __init__.py myapp/ myfile.py And then in myfile.py # These imports should fetch modules from the original django package from django import models from django.core.urlresolvers import reverse # I would like this following import statement to grab a custom version of settings # that I define in local_django/conf/settings.py from django.conf import settings def foo(): return settings.some_setting Can I do some magic with the __import__ statement in myproject/__init__.py to accomplish this? Is there a more "pythonic" way to achieve this?

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  • Select *, max(date) works in phpMyAdmin but not in my code

    - by kdobrev
    OK, my statement executes well in phpMyAdmin, but not how I expect it in my php page. This is my statement: SELECT egid , group_name , limit , MAX( date ) FROM employee_groups GROUP BY egid ORDER BY egid DESC ; This is may table: CREATE TABLE employee_groups ( egid int(10) unsigned NOT NULL, date date NOT NULL, group_name varchar(50) NOT NULL, limit smallint(5) unsigned NOT NULL, PRIMARY KEY (egid,date) ) ENGINE=MyISAM DEFAULT CHARSET=cp1251; I want to extract the most recent list of groups, e.g. if a group has been changed I want to have only the last change. And I need it as a list (all groups).

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  • Is it possible for a Grails Domain to have no 'id'?

    - by firnnauriel
    Is it possible to create a table that has no 'id'? For example, this is my domain: class SnbrActVector { int nid String term double weight static mapping = { version false id generator: 'identity' } static constraints = { } } When I run this SQL statement, it fails: insert into snbr_act_vector values (5, 'term', 0.5) I checked the table and 'id' is already set to autoincrement. I'm thinking that another option is to remove the 'id' itself. Or is there another workaround for this? Please assume that it is not an option to change the givent SQL statement.

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  • Seperate compilation in C++

    - by Pat Murray
    Suppose you are creating a class with multiple .cpp files (which each contain the implementation of a member function) and have the class' declaration in a .h file. Also, each .cpp file includes the .h file via the include directive. I was told that if you change the implementation of any of the member functions (.cpp files) that you will have to recompile every .cpp file in order to run the program. That is, if I had 5 member functions (each implemented in a .cpp file) and I changed the implementation of 1 of the .cpp files I would have to compile the 1 .cpp file I changed AND the 4 other .cpp files I didn't change in order to correctly run my program. My question, if the previous statement is true, is why is the statement is true? Any insight on this concept would be helpful.

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  • What is the benefit to wrapping every sql/stored proc invocation in a transaction?

    - by MatthewMartin
    The following code executes one stored procedure. The stored procedure has only one command in it. Is there any benefit to wrapping everything in a transaction, even it only has one SQL statement in it (or one stored proc that has only one sql statement)? In the sample code below, if the delete fails, it fails. There is nothing else to be rolled back (it seems). So why is everything wrapped in a transaction anyhow? using (ITransactionManager transMan = repository.TransactionManager()) using (IController controller = repository.Controller()) { transMan.BeginTransaction(); try { //DELETE FROM myTable where Id=@id controller.Delete(id); transMan.CommitTransaction(); } catch { transMan.RollbackTransaction(); throw; } }

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  • Bug in Programming Interviews Exposed?

    - by Sam
    Hi, I could not find an errata for the 2nd edition of this book. My question concerns the if-statement in the following piece of code. void removeHead (Node ** head) { Node * temp; if (!(*head)) { temp = (*head)->next; delete *head; *head = temp; } } So I understand that the point of the if-statement is to check if the Node is null. However by adding an additional "!" to the evaluation, wouldn't this negate the false value of null? Would it be correct to change it to something like: if (*head) { ... } Also if anyone knows where I can find an official errata for the 2nd edition that would be great. Thanks, Sam

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  • MySQL ON DUPLICATE KEY UPDATE issue

    - by user644347
    Hi could some one look at this and tell me where I am going wrong. I have an SQL statement that when I echo using php I get this to screen INSERT INTO 'moviedb'.'genre' SET 'GenreID' = '18' , 'GenreName' = 'Drama' ON DUPLICATE KEY UPDATE 'GenreName' = 'Drama' WHERE 'GenreID' = '18' INSERT INTO 'moviedb'.'genre' SET 'GenreID' = '16' , 'GenreName' = 'Animation' ON DUPLICATE KEY UPDATE 'GenreName' = 'Animation' WHERE 'GenreID' = '16' And here is the statement $sql="INSERT INTO 'moviedb'.'genre' SET 'GenreID' = '{$genresID[$i]}' , 'GenreName' = '{$genreName[$i]}' ON DUPLICATE KEY UPDATE 'GenreName' = '{$genreName[$i]}' WHERE 'GenreID' = '{$genresID[$i]}'"; This is the error I recieve: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''moviedb'.'genre' SET 'GenreID' = '18' , 'GenreName' = 'Drama' ON DUPLICATE KEY ' at line 1 Any help would be greatly appreciated, thanks in advance.

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  • Can anyone tell me what is wrong with my create trigger syntax?

    - by Travis
    I am experimenting with triggers for the first time. When I try to create a trigger using the following: CREATE TRIGGER t_foldersPrivate BEFORE DELETE ON foldersPrivate FOR EACH ROW BEGIN DELETE FROM programs WHERE folderType = '0' AND folderID = OLD.ID; END; I receive the following error: `1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 3` (mysql 5.1.37) If I get rid fo the delete statement the create trigger statement works fine. So I am assuming it must have something to do with that. But for the life of me I'm not sure what...

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  • mysql_query where statment help

    - by Anders Kitson
    I am retrieving values from the url with the GET method and then using a if statement to determine of they are there then query them against the database to only show those items that match them, i get an unknown error with your request. here is my code $province = $_GET['province']; $city = $_GET['city']; if(isset($province) && isset($city) ) { $results3 = mysql_query("SELECT * FROM generalinfo WHERE province = $province AND city = $city ") or die( "An unknown error occurred with your request"); } else { $results3 = mysql_query("SELECT * FROM generalinfo"); } /*if statement ends*/

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  • Semantic errors

    - by gautam kumar
    Can semantic errors be detected by the compiler or not? If not when do the errors get detected? As far as I know semantic errors are those errors which result from the expressions involving operators with incorrect number/type of operands. For example: n3=n1*n2;//n1 is integer, n2 is a string, n3 is an integer The above statement is semantically incorrect. But while reading C Primer Plus by Stephen Prata I found the following statement The compiler does not detect semantic errors, because they don't violate C rules. The compiler has no way of divining your true intentions. That leaves it to you to find these kinds of errors. One way is to compare what a program does to what you expected it to do. If not the compiler, who detects those errors? Am I missing something?

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  • Microsoft SQL Server 2005/2008 SSIS are oversized

    - by Ice
    In this case i'm old style and loved 'my fathers DTS' from SQL 2000. Most of the cases i have to import a flatfile into a table. In a second step i use some procedures (with the new MERGE-Statement) to process the imported content. For Export, i define a export-table and populate it with a store proc (containing a MERGE-Statement) and in a second step the content will be exported to a flat file. In some cases there is no flat file because there is annother sql-server or in rare cases an ODBC-Connection to a sybase or similar. What do you think? When it comes to complex ETL-Stuff the SSIS may be the right tool...but i haven't seen such a case yet.

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  • Why the compiler doesn't complain about this error ?

    - by M.H
    Hi I am writing some java questions to help my friends in the java exam. I wrote a question and I supposed that three errors will occurred in the code but the compiler complained only about two. the code is : class MyClass { static MyClass() { System.out.println("I am The First Statement here!"); this(); } } I expected the following errors : the constructor can't be static this can't be in a static function (since the constructor isn't valid) this here should be the first statement. NetBeans isn't complaining about the second error here. why ?

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  • update each recordset with datareader

    - by knittl
    hi, my situation is the following: i have a datareader and loop over all records returned by a select statement and then call a function with a value from that row. but now i need to update a column in each row, after the function has been called. using a separate update statement seems like a huge overkill. what's the best method to do so? i've heard about dataadapters and datasets—but the only thing i know is that they exist, not how to use them (properly) in this case. platform is c# with sql server

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  • Why does UIActionSheet cancel crahes my App?

    - by Tim Büthe
    I try to use the UIActionSheet within my iPhone App but have the following problem. When I tap the cancel button "I don't", the app crashes. When I remove the NSLog statement from the actionSheet:clickedButtonAtIndex: it does not. The "Yes, do it" button works just fine and I see the log statement in the console. What's wrong? - (void) doItWithConfirm { UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:@"do you really wanna do it?" delegate:self cancelButtonTitle:@"I don't" destructiveButtonTitle: nil otherButtonTitles:@"Yes, do it", nil]; [actionSheet showInView:self.view]; [actionSheet release]; } - (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex { NSLog(@"buttonIndex: %@", buttonIndex); }

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  • iOS Development: Why isn't my try block catching the exception?

    - by BeachRunnerJoe
    Hi. I have an exception being thrown in my code, but when I wrap it in an try/catch block, it doesn't get caught. The NSLog statement is never called in the catch block. Here's the code... NSInteger quoteLength; [data getBytes:(void *)&quoteLength range:NSMakeRange(sizeof(messageType), sizeof(quoteLength))]; @try { //Debugger stack trace shows an NSException being thrown on this statement NSData *stringData = [data subdataWithRange:NSMakeRange(sizeof(messageType) + sizeof(quoteLength), [data length])]; NSString *quote = [[NSString alloc] initWithData:stringData encoding:NSUTF8StringEncoding]; NSLog(@"received quote: %@",quote); [quote release]; } @catch (NSException * e) { NSLog(@"Exception Raised: %@", [e reason]); } Why doesn't it get caught? Thanks so much!

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  • How do I take the advantage of the variable column key/value structure of Cassandra

    - by icejade
    If I have to predefine all the columns, how do I take the advantage of the variable column key/value structure of cassandra? If I use update table command, it will insert null for all the rows which don't have that column. This is same as relational DB. For example, for contact column family, I have name, phone, email. I have 100 contacts have all 3 field. Then number 101 contact has skype id which I want to add. If I use insert statement, it won't let me add skypeid since it's not defined in the CF. So I have to run alter statement to change the CF, then all the first 100 contacts will have a null field for each of them.

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  • From xcode not able to execute DISTINCT keyword for sqlite

    - by mac
    -(void) readProductsFromDatabase { // Setup the database object sqlite3 *database; // Init the animals Array products = [[NSMutableArray alloc] init]; // Open the database from the users filessytem if(sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) { NSLog(@"db opened"); // Setup the SQL Statement and compile it for faster access const char *sqlStatement = "SELECT DISTINCT productname FROM iphone "; sqlite3_stmt *compiledStatement; if(sqlite3_prepare_v2(database, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK) { // Loop through the results and add them to the feeds array while(sqlite3_step(compiledStatement) == SQLITE_ROW) { NSLog(@"inside sqlite3 prepare"); // Read the data from the result row NSString *aName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 2)]; } } // Release the compiled statement from memory sqlite3_finalize(compiledStatement); } sqlite3_close(database); } My problem is const char *sqlStatement = "SELECT DISTINCT productname FROM iphone "; This line not executing ,i am using sqlite3, thanks in advance,

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  • Return Integer value from SSIS execute SQL Task

    - by Bokhari
    I am using SQL Server 2005 Business Intelligence Studio and struggling with returning an integer value from a very simple execute SQL Task. For a very simple test, I wrote the SQL Statement as: Select 35 As 'TotalRecords' Then, I specified ResultSet as ResultName = TotalRecords and VariableName = User::TotalRecords When I execute this, the statement is executed but the variable doesn't have the updated value. However, it has the default value that I specified while variable definition. The return of a date variable works, but integer variable isn't working. The type of User::TotalRecords specified is Int32 in a package scope. Thanks for any hints

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