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  • Rails 3 MySQL 2 reports an error in what looks to be valid SQL syntax

    - by John Judd
    I am trying to use the following bit of code to help in seeding my database. I need to add data continually over development and do not want to have to completely reseed data every time I add something new to the seeds.rb file. So I added the following function to insert the data if it doesn't already exist. def AddSetting(group, name, value, desc) Admin::Setting.create({group: group, name: name, value: value, description: desc}) unless Admin::Setting.find_by_sql("SELECT * FROM admin_settings WHERE group = '#{group}' AND name = '#{name}';").exists? end AddSetting('google', 'analytics_id', '', 'The ID of your Google Analytics account.') AddSetting('general', 'page_title', '', '') AddSetting('general', 'tag_line', '', '') This function is included in the db/seeds.rb file. Is this the right way to do this? However I am getting the following error when I try to run it through rake. rake aborted! Mysql2::Error: 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 'group = 'google' AND name = 'analytics_id'' at line 1: SELECT * FROM admin_settings WHERE group = 'google' AND name = 'analytics_id'; Tasks: TOP => db:seed (See full trace by running task with --trace) Process finished with exit code 1 What is confusing me is that I am generating correct SQL as far as I can tell. In fact my code generates the SQL and I pass that to the find_by_sql function for the model, Rails itself can't be changing the SQL, or is it? SELECT * FROM admin_settings WHERE group = 'google' AND name = 'analytics_id'; I've written a lot of SQL over the years and I've looked through similar questions here. Maybe I've missed something, but I cannot see it.

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  • IIS6 throws error for jquery.

    - by user309557
    Hi, on my master page, I have referenced jquery file. I am doing simple hover function. When mouse hover, I change the css and when hover out, change the css back to originial. Nothing fancy. but my page throws jquery error when I run in IIS6 on server 2003. When I run on IIS5.1 on local xp machine, it works perfectly fine. Any idea? I access both pages from my machine so IE settings is not the problem. I opened the both js file and the error line is nothing but the end of the file ( i.e last line of the js file) Webpage error details User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; OfficeLiveConnector.1.4; OfficeLivePatch.1.3) Timestamp: Mon, 5 Apr 2010 21:59:18 UTC Message: Syntax error Line: 4377 Char: 2 Code: 0 URI: server-test/myapplication/Scripts/jquery-1.3.2.js (removed the link because stackoverflow does not allow me to put more than one link) Message: Syntax error Line: 6183 Char: 2 Code: 0 URI: server-test/myapplication/Scripts/jquery-1.3.2-vsdoc.js (removed the link because stackoverflow does not allow me to put more than one link) Message: Object expected Line: 189 Char: 9 Code: 0 URI: http://server-test/myapplication/

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  • C macro issue: redefinition of functions / structure

    - by Andrei Ciobanu
    Given the following code (it's a macro that generates code for a list data structure, based on the contained type). list.h #ifndef _LIST_H #define _LIST_H #ifdef __cplusplus extern "C" { #endif #define LIST_TEMPLATE_INIT(type) \ typedef struct __list_s_##type { \ struct __list_s_##type *next; \ type value; \ } __list_##type; \ \ __list_##type * __list_##type##_malloc(type value){ \ __list_##type * list = NULL; \ list = malloc(sizeof(*list)); \ list->value = value; \ return list; \ }\ \ void __list_##type##_free(__list_##type *list){\ __list_##type * back = list;\ while(list=list->next){\ free(back);\ back = list;\ }\ } #define LIST_TYPE(type) __list_##type #define LIST_MALLOC(type,value) __list_##type##_malloc(value) #define LIST_FREE(type,list) __list_##type##_free(list) #define LIST_DATA(list) (list->value) #ifdef __cplusplus } #endif #endif /* _LIST_H */ And here is how the above code works: #include <stdio.h> #include <stdlib.h> #include "list.h" /* * */ LIST_TEMPLATE_INIT(int) int main(int argc, char** argv) { LIST_TYPE(int)* list = NULL; list = LIST_MALLOC(int, 5); printf("%d",LIST_DATA(list)); LIST_FREE(int,list); return (0); } My question, is it possible to somehow be able to call : LIST_TEMPLATE_INIT(int), as many times as I want, in a decentralized fashion ? The current issue with this right now is that calling LIST_TEMPLATE_INIT(int) in another file raise compilation errors (because of function redefinition): Example of error: error: redefinition of ‘struct __list_s_int’

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  • change div text on radion button click

    - by pisi
    I want to put the radio button value in the status div. The text of status div should change, according to the radio button selected by the user. The code that I used bellow is not working. Please help. Thanks! HTML code: <form action=""> <input type="radio" name="sex" value="male">Male<br> <input type="radio" name="sex" value="female">Female<br> <div id="status"></div> </form>? JS code: $(document).ready(function () { RadioStatus=""; $("input[type='radio']:checked").each( function() { if ($(this).attr('checked');) RadioStatus=$(this).val(); $("#status").text(RadioStatus); }); $("input[type='radio']").change(function() { RadioStatus= $('input[type='radio']:checked').val() $('#status').text(RadioStatus); }); });

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  • SQL Server Connection Timeout C#

    - by Termin8tor
    First off I'd like to let everyone know I have searched my particular problem and can't seem to find what's causing my problem. I have an SQL Server 2008 instance running on a network machine and a client I have written connecting to it. To connect I have a small segment of code that establishes a connection to an sql server 2008 instance and returns a DataTable populated with the results of whatever query I run against the server, all pretty standard stuff really. Anyway the issue is, whenever I open my program and call this method, upon the first call to my method, regardless as to what I've set my Connection Timeout value as in the connection string, it takes about 15 seconds and then times out. Bizarrely though the second or third call I make to the method will work without a problem. I have opened up the ports for SQL Server on the server machine as outlined in this article: How to Open firewall ports for SQL Server and verified that it is correctly configured. Can anyone see a particular problem in my code? string _connectionString = "Server=" + @Properties.Settings.Default.sqlServer + "; Initial Catalog=" + @Properties.Settings.Default.sqlInitialCatalog + ";User Id=" + @Properties.Settings.Default.sqlUsername + ";Password=" + @Properties.Settings.Default.sqlPassword + "; Connection Timeout=1"; private DataTable ExecuteSqlStatement(string command) { using (SqlConnection conn = new SqlConnection(_connectionString)) { try { conn.Open(); using (SqlDataAdapter adaptor = new SqlDataAdapter(command, conn)) { DataTable table = new DataTable(); adaptor.Fill(table); return table; } } catch (SqlException e) { throw e; } } } The SqlException that is caught at my catch is : "Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding." This occurs at the conn.Open(); line in the code snippet I have included. If anyone has any ideas that'd be great!

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  • User input being limited to the alphabet in python

    - by Danger Cat
    I am SUPER new to programming and have my first assignment coming up in python. I am writing a hangman type game, where users are required to guess the word inputted from the other user. I have written most of the code, but the only problem I am having is when users have to input the word, making sure it is only limited to the alphabet. The code I have so far is : word = str.lower(raw_input("Type in your secret word! Shhhh... ")) answer = True while answer == True: for i in range(len(word)): if word[i] not in ("abcdefghijklmnopqrstuvwxyz"): word = raw_input("Sorry, words only contain letters. Please enter a word ") break else: answer = False This works while I input a few tries, but eventually will either exit the loop or displays an error. Is there any easier way to use this? We've really only covered topics up to loops in class, and break and continue are also very new to me. Thank you! (Pardon if the code is sloppy, but as I said I am very new to this....)

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  • Spring MVC - Set an actionURL parameter with Javascript

    - by jeffl8n
    Is it possible to dynamically set a Spring MVC portlet:actionURL portlet:param using javascript? I have tried with the following code, but the id value always comes across as null to the controller. I have verified that setting the portlet:param manually passes the value correctly: <portlet:param name="id" value="2" /> I have also verified the value in the javascript is being set correctly and is not null. (Note: I've changed the variable names, etc. from the original code to simplify it and obfuscate it since it is my employer's code.) JSP: <portlet:actionURL var="modifyURL"> <portlet:param name="do" value="modify" /> <portlet:param name="id" value="${model.id}" /> </portlet:actionURL> ... <form:form action="${modifyURL}" id="modifyForm" modelAttribute="model"> <form:hidden path="id" id="id" /> </form:form> Javascript called when the update URL is clicked: function update() { document.forms[0]["id"].value = selectedId; document.forms[0].submit(); } Controller: @RequestMapping(params = {"do=modify"}) public void modify(@ModelAttribute("model") Model model, @RequestParam(value = "id", required=true) Long id, ActionRequest request, ActionResponse response, SessionStatus sessionStatus, ModelMap modelMap) { ....

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  • Is there a Java data structure that is effectively an ArrayList with double indicies and built-in in

    - by Bob Cross
    I am looking for a pre-built Java data structure with the following characteristics: It should look something like an ArrayList but should allow indexing via double-precision rather than integers. Note that this means that it's likely that you'll see indicies that don't line up with the original data points (i.e., asking for the value that corresponds to key "1.5"). As a consequence, the value returned will likely be interpolated. For example, if the key is 1.5, the value returned could be the average of the value at key 1.0 and the value at key 2.0. The keys will be sorted but the values are not ensured to be monotonically increasing. In fact, there's no assurance that the first derivative of the values will be continuous (making it a poor fit for certain types of splines). Freely available code only, please. For clarity, I know how to write such a thing. In fact, we already have an implementation of this and some related data structures in legacy code that I want to replace due to some performance and coding issues. What I'm trying to avoid is spending a lot of time rolling my own solution when there might already be such a thing in the JDK, Apache Commons or another standard library. Frankly, that's exactly the approach that got this legacy code into the situation that it's in right now.... Is there such a thing out there in a freely available library?

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  • Applied style in WPF ignores properties.

    - by Quenton Jones
    Here's the conundrum. In two different places in my application, I use a border with the exact same appearance. In an never-ending fight against code bloat and unmanageable code, I want to define the border's appearance in a style to use when I create the border. Strangely, several of the properties I set are being ignored. Here's the code I use to create the style. Simple enough. Style borderStyle = new Style(typeof(Border)); borderStyle.Setters.Add(new Setter(Border.BorderBrushProperty, Brushes.Black)); borderStyle.Setters.Add(new Setter(Border.BorderThicknessProperty, new Thickness(4))); borderStyle.Setters.Add(new Setter(Border.OpacityProperty, 1.0)); return borderStyle; But when I set the style, the opacity property is left at its original value of 0.7. I have also tried setting the background of the border to a brush I created. It too is ignored. Thanks for any insights you may have.

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  • PHP download page: file_exists() returns true, but browser returns 'page not found'

    - by Chris
    I'm using PHP for a file download page. Here's a snippet of the problem code: if (file_exists($attachment_location)) { header($_SERVER["SERVER_PROTOCOL"] . " 200 OK"); header("Cache-Control: public"); // needed for i.e. header("Content-Type: application/zip"); header("Content-Transfer-Encoding: Binary"); header("Content-Length:".filesize($attachment_location)); header("Content-Disposition: attachment; filename=file.zip"); readfile($attachment_location); die("Hooray"); } else { die("Error: File not found."); } This code works absolutely fine when testing locally, but after deploying to the live server the browser returns a 'Page not found' error. I thought it might be an .htaccess issue, but all .htaccess files on the live server are identical to their local counterparts. My next guess would be the live server's PHP configuration, but I have no idea what PHP setting might cause this behaviour. The file_exists() function always returns true - I've checked this on the live server and it's always correctly picking up the file, its size etc., so it does have a handle on the file. It just won't perform the download! The main site is a Wordpress site, but this code isn't part of a Wordpress page - it's in a standalone directory within the site root. UPDATE: is_file() and is_readable() are both returning true for the file, so that's not the problem. The specific line that is causing the problem is: readfile($attachment_location) Everything up until that point is super happy.

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  • onKeypress Enter Key event on textfield not working in Chrome

    - by rlcrews
    I have a question along the same vein as the one asked here regarding how the enter key is handled in chrome. The effect I am trying to accomplish is to allow the enter key to call a click event of one a button while focus in within the current field. To accomplish this I am using the following code: javascript: <script type="text/javascript"> //attempting to capture keypress for chrome here but this is not working $("#txtContainer").keypress(function (e) { if (e.keyCode == '13') { e.preventDefault(); doClick(buttonname, e); return false; } }); function doClick(buttonName, e) { var key; if (window.event) key = window.event.keyCode; //IE else key = e.which; //firefox if (key == 13) { var btn = document.getElementById(buttonName); if (btn != null) { btn.click(); event.keyCode = 0 } } } </script> within the aspx <form id="form1" runat="server"> <div> <asp:LinkButton ID="newBtn" runat="server" OnClick="btnLogin_Click" Text="ASP Link" /> <asp:TextBox ID="txtContainer" runat="server" Width="100" /> <asp:Label ID="time_lbl" runat="server" /> </div> </form> and within the code behind aspx.cs protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { txtContainer.Attributes.Add("onKeyPress", "doClick('" + newBtn.ClientID + "',event)"); } } public void btnLogin_Click(object sender, EventArgs e) { time_lbl.Text = txtContainer.Text; } The above code works fine in FF and IE however chrome continues to submit the entire form vs. capturing the keypress on the enterkey. Thank you for any suggestions.

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  • Persistent Objects in ASP.NET

    - by user204588
    Hello, I'm trying to find the best way to persist an object or in use the same object at a later point in the code. So, I create an object, then you're redirected to another page(a form) that needs to use variables from that object. That form is submitted to a third party and there is stuff done on their end and then they request a page on my application that runs some more code and needs the objects variables again. I thought about Database but this is all done at once. This is done during a user checkout process and after it's over, there's no reason to retrieve this object again. So adding and retrieving from a database seems like it would be overkill and I think it would make the process slower. Right now I'm using Session but I keep hearing not to use that but no one is really saying why I shouldn't except it is bad practice. I can't really use post back values because the pages don't work that way. The checkout process starts off in a dll code that redirects to the form that is submitted to the third party and the a page is requested by the third party. So, I'm not really sure of the best way. What are all the options and what does everyone recommend as the best way?

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  • image transistion

    - by Jeff Main
    Hi all. I've gotten stuck again. I've got an image (album cover) that I'll be changing in code behind, and wish to basicaly do the following. When a new album cover image is determine and aquired, I want the current image in the image control to fade out, get updated with the new cover, and then fade back in. I'm not seeing very many good examples on how to accomplish this in code behind. The following was my latest failed attempt... if (currentTrack != previousTrack) { BitmapImage image = new BitmapImage(); image.BeginInit(); image.CacheOption = BitmapCacheOption.OnLoad; image.CreateOptions = BitmapCreateOptions.IgnoreImageCache; image.UriSource = new Uri(Address, UriKind.Absolute); image.EndInit(); Storyboard MyStoryboard = new Storyboard(); DoubleAnimation FadeOut = new DoubleAnimation(); FadeOut.From = 1.0; FadeOut.To = 0.0; FadeOut.Duration = new Duration(TimeSpan.FromSeconds(.5)); MyStoryboard.Children.Add(FadeOut); Storyboard.SetTargetName(FadeOut, CoverArt.Name); Storyboard.SetTargetProperty(FadeOut, new PropertyPath(Rectangle.OpacityProperty)); CoverArt.Source = image; DoubleAnimation Fadein = new DoubleAnimation(); Fadein.From = 0.0; Fadein.To = 1.0; Fadein.Duration = new Duration(TimeSpan.FromSeconds(.5)); MyStoryboard.Children.Add(Fadein); Storyboard.SetTargetName(Fadein, CoverArt.Name); Storyboard.SetTargetProperty(Fadein, new PropertyPath(Rectangle.OpacityProperty)); MyStoryboard.Begin(this); } I'd prefer to do this in code behind simply because that is where I'm aquiring the image. Otherwise, I'm not sure how I'd trigger it. An example would be greatly appriciated. Thanks.

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  • Mercurial: Class library that will exist for both .NET 3.5 and 4.0?

    - by Lasse V. Karlsen
    I have a rather big class library written in .NET 3.5 that I'd like to upgrade to make available for .NET 4.0 as well. In that process, I will rip out a lot of old junk, and rewrite some code to better take advantage of the new classes and support in .NET 4.0 (like TPL.) The class libraries will thus diverge, but still be similar enough that some bug-fixes can be done to both in the same manner. How should I best organize this class library in Mercurial? I'm using Kiln (fogbugz) if that matters. I'm thinking: Named branches in one repository, can then transplant any bugfixes from one to the other Unnamed branches in one repository, can also transplant, but I think this will look messy Separate repositories, will have to reimplement the bugfixes (or use a non-mercurial-integraded compare tool to help me) What would you do? (any other alternatives that I haven't though of is welcome as well.) Note that the class libraries will diverge pretty heavily in areas, I have some remnants of old collection-type code that does something similar to Linq that I will remove, and some code that uses it that I will rewrite to use the Linq-methods instead. As such, just copying the project files and using #if NET40..#endif sections is not going to work out. Also, the 3.5 version of the class library will not be getting many new features, mostly just critical bug-fixes, so keeping both versions equally "alive" isn't really necessary. Thus, separate copies of all the files are good enough.

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  • PHP & MySQL Pagination Update Help

    - by TaG
    Its been a while since I updated my pagination on my web page and I'm trying to add First and Last Links to my pagination as well as the ... when the search results are to long. For example I'm trying to achieve the following in the example below. Can some one help me fix my code so I can update my site. Thanks Previous First 1 2 3 4 5 6 7 ... 199 200 Last Next I currently have the following displayed using my code. Previous 1 2 3 4 5 6 7 Next Here is the part of my pagination code that displays the links. if ($pages > 1) { echo '<br /><p>'; $current_page = ($start/$display) + 1; if ($current_page != 1) { echo '<a href="index.php?s=' . ($start - $display) . '&p=' . $pages . '">Previous</a> '; } for ($i = 1; $i <= $pages; $i++) { if ($i != $current_page) { echo '<a href="index.php?s=' . (($display * ($i - 1))) . '&p=' . $pages . '">' . $i . '</a> '; } else { echo '<span>' . $i . '</span> '; } } if ($current_page != $pages) { echo '<a href="index.php?s=' . ($start + $display) . '&p=' . $pages . '">Next</a>'; } echo '</p>'; }

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  • jQuery fade li elemet and cycle it when mouse hovered.

    - by Pennf0lio
    I'm trying to recreate an effect in jQuery, where an element(<li> <img>) will be cycled and has a fading effect when hovered. The '<li>' contains '<img>' (image screenshots). when the mouse is on top of element it will keep cycling all that are in '<ul>' with a fading effect. when the mouse is away it will stop cycling the list. I also want to add a pager where you can navigate to the list. My Existing Code: link text My Problem: The current code has some problem with the pagination, it added all images that can be seen on the code. instead of 1-8 only, it continued to add another 1-8 and another. Second problem is, It also start cycling and fading when the page loads. The cycling and fading should only be working when the mouse is on top of the element. I don't know if the 'Cycle Plugin' is really required on this approach, I wan't it to be minimal as much as possible. I just use 'Cycle Plugin' because it's a quick answer to my problem. The effect i'm trying to achieve: link text (WARNING: Contains some Pornography), Sorry of my example, I tried finding other alternative but no luck. Thanks and merry xmas!

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  • directory traversal in Java using different regular and enhanced for loops

    - by user3245621
    I have this code to print out all directories and files. I tried to use recursive method call in for loop. With enhanced for loop, the code prints out all the directories and files correctly. But with regular for loop, the code does not work. I am puzzled by the difference between regular and enhanced for loops. public class FileCopy { private File[] childFiles = null; public static void main(String[] args) { FileCopy fileCopy = new FileCopy(); File srcFile = new File("c:\\temp"); fileCopy.copyTree(srcFile); } public void copyTree(File file){ if(file.isDirectory()){ System.out.println(file + " is a directory. "); childFiles = file.listFiles(); /*for(int j=0; j<childFiles.length; j++){ copyTree(childFiles[j]); } This part is not working*/ for(File a: childFiles){ copyTree(a); } return; } else{ System.out.println(file + " is a file. "); return; } } }

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  • Adobe Air, packaged install fails with my trace routine... how come?

    - by artie scie
    I cobbled together some code from here and there for a trace I like... it generates an error to get a stack trace and picks out the traced routine name, I like that detail in the trace log. Problem: it fails in an installed AIR file. I wonder why? I don't expect it to do anything as is... just, I'd prefer it not cause the program to fail! tx artie enter code here static public function XTRACE( ... traceArgs ):void { try { throw new Error(); // make a stack } catch (e:Error) { var stack:String = e.getStackTrace(); var frames:Array = stack.split("\n"); var myFrame:String = String(frames[2]); myFrame = myFrame.replace("\t", ""); // "at " can be followed by some part of the package // you don't want to see. E.g., if your code is all in // com.foo.bar, you can put "at com.foo.bar." so as not // to crowd the display myFrame = myFrame.substr("at ".length); myFrame = myFrame.substring(0, myFrame.indexOf("[")); var now:Date = new Date(); trace(new Date().toLocaleTimeString() + ":" + myFrame + ": " + traceArgs.join(" ")); } }

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  • Automating Excel through the PIA makes VBA go squiffy.

    - by Jon Artus
    I have absolutely no idea how to start diagnosing this, and just wondered if anyone had any suggestions. I'm generating an Excel spreadsheet by calling some Macros from a C# application, and during the generation process it somehow breaks. I've got a VBA class containing all of my logging/error-handling logic, which I instantiate using a singleton-esque accessor, shown here: Private mcAppFramework As csys_ApplicationFramework Public Function AppFramework() As csys_ApplicationFramework If mcAppFramework Is Nothing Then Set mcAppFramework = New csys_ApplicationFramework Call mcAppFramework.bInitialise End If Set AppFramework = mcAppFramework End Function The above code works fine before I've generated the spreadsheet, but afterwards fails. The problem seems to be the following line; Set mcAppFramework = New csys_ApplicationFramework which I've never seen fail before. If I add a watch to the variable being assigned here, the type shows as csys_ApplicationFramework/wksFoo, where wksFoo is a random worksheet in the same workbook. What seems to be happening is that while the variable is of the right type, rather than filling that slot with a new instance of my framework class, it's making it point to an existing worksheet instead, the equivalent of Set mcAppFramework = wksFoo which is a compiler error, as one might expect. Even more bizarrely, if I put a breakpoint on the offending line, edit the line, and then resume execution, it works. For example, I delete the word 'New' move off the line, move back, re-type 'New' and resume execution. This somehow 'fixes' the workbook and it works happily ever after, with the type of the variable in my watch window showing as csys_ApplicationFramework/csys_ApplicationFramework as I'd expect. This implies that manipulating the workbook through the PIA is somehow breaking it temporarily. All I'm doing in the PIA is opening the workbook, calling several macros using Excel.Application.Run(), and saving it again. I can post a few more details if anyone thinks that it's relevant. I don't know how VBA creates objects behind the scenes or how to debug this. I also don't know how the way the code executes can change without the code itself changing. As previously mentioned, VBA has frankly gone a bit squiffy on me... Any thoughts?

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  • Does operator precedence in C++ differ for pointers and iterators?

    - by oraz
    The code below demonstrates this difference: #include <iostream> #include <string> int main() { char s[] = "ABCD"; std::string str(s); char *p = s; while(*p) { *p++ = tolower(*p); // <-- incr after assignment } std::cout << s << std::endl; std::string::iterator it = str.begin(), end = str.end(); while(it != end) { *it++ = tolower(*it); // <-- incr before assignment ? } std::cout << str << std::endl; return 0; } the code above outputs: abcd bcd if we separate assignment operation and increment operator: while(it != end) { *it = tolower(*it); // <-- incr before assignment ? it++; } the output will be as expected. What's wrong with the original code? $ g++ --version g++ (GCC) 3.4.4 (cygming special, gdc 0.12, using dmd 0.125) Copyright (C) 2004 Free Software Foundation, Inc.

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  • Learning Java and logic using debugger. Did I cheat?

    - by centr0
    After a break from coding in general, my way of thinking logically faded (as if it was there to begin with...). I'm no master programmer. Intermediate at best. I decided to see if i can write an algorithm to print out the fibonacci sequence in Java. I got really frustrated because it was something so simple, and used the debugger to see what was going on with my variables. solved it in less than a minute with the help of the debugger. Is this cheating? When I read code either from a book or someone else's, I now find that it takes me a little more time to understand. If the alghorithm is complex (to me) i end up writing notes as to whats going on in the loop. A primitive debugger if you will. When you other programmers read code, do you also need to write things down as to whats the code doing? Or are you a genius and and just retain it?

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  • Doubt on pointer conversion

    - by Simone
    Suppose we have the following code: #include <iostream> struct A { virtual void f() { std::cout << "A::f()" << std::endl; } }; struct B: A { void f() { std::cout << "B::f()" << std::endl; } }; void to_A(void* voidp) { A* aptr = static_cast<A*>(voidp); aptr->f(); } void to_B(void* voidp) { B* bptr2 = static_cast<B*>(voidp); bptr2->f(); } int main() { B* bptr = new B; void* voidp = bptr; to_A(voidp); // prints B::f() to_B(voidp); // prints B::f() } is this code guaranteed to always work as in the code comments or is it UB? AFAIK it should be ok, but I'd like to be reassured.

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  • Dynamic programming Approach- Knapsack Puzzle

    - by idalsin
    I'm trying to solve the Knapsack problem with the dynamical programming(DP) approach, with Python 3.x. My TA pointed us towards this code for a head start. I've tried to implement it, as below: def take_input(infile): f_open = open(infile, 'r') lines = [] for line in f_open: lines.append(line.strip()) f_open.close() return lines def create_list(jewel_lines): #turns the jewels into a list of lists jewels_list = [] for x in jewel_lines: weight = x.split()[0] value = x.split()[1] jewels_list.append((int(value), int(weight))) jewels_list = sorted(jewels_list, key = lambda x : (-x[0], x[1])) return jewels_list def dynamic_grab(items, max_weight): table = [[0 for weight in range(max_weight+1)] for j in range(len(items)+1)] for j in range(1,len(items)+1): val= items[j-1][0] wt= items[j-1][1] for weight in range(1, max_weight+1): if wt > weight: table[j][weight] = table[j-1][weight] else: table[j][weight] = max(table[j-1][weight],table[j-1][weight-wt] + val) result = [] weight = max_weight for j in range(len(items),0,-1): was_added = table[j][weight] != table[j-1][weight] if was_added: val = items[j-1][0] wt = items[j-1][1] result.append(items[j-1]) weight -= wt return result def totalvalue(comb): #total of a combo of items totwt = totval = 0 for val, wt in comb: totwt += wt totval += val return (totval, -totwt) if totwt <= max_weight else (0,0) #required setup of variables infile = "JT_test1.txt" given_input = take_input(infile) max_weight = int(given_input[0]) given_input.pop(0) jewels_list = create_list(given_input) #test lines print(jewels_list) print(greedy_grab(jewels_list, max_weight)) bagged = dynamic_grab(jewels_list, max_weight) print(totalvalue(bagged)) The sample case is below. It is in the format line[0] = bag_max, line[1:] is in form(weight, value): 575 125 3000 50 100 500 6000 25 30 I'm confused as to the logic of this code in that it returns me a tuple and I'm not sure what the output tuple represents. I've been looking at this for a while and just don't understand what the code is pointing me at. Any help would be appreciated.

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  • c++ simple conditional logging

    - by Sunny
    Disclaimer: I'm not a c++ developer, I can only do basic things. (I understand pointers, just my knowledge is so rusty, I haven't touch c/c++ for about 20 years :) ) The setup: I have an Outlook addin, written in C#/.Net 1.1. It uses a c++ shim to load. Usually, this works pretty well, and I use in my c# code nlog for logging purposes. But sometimes, the addin fails to load, i.t. it does not hit the managed code at all for me to be able to investigate the problem from the log files. So, I need to hook some basic logging into the c++ shim - just writing in a file. I need to make it as simple as possible for our users to enable. Actually I would prefer not to ship it by default. I was thinking about something, which will check if a specific dll is present (the logging dll), and if so, to use it. Otherwise, it will just not log anything. That way, when I have a user with such a problems, I can send him only the logging dll, the user will save it in the runtime directory, and I'll have the file. I guess this have to be done with some form a factory solution, which returns either a dummy logger, or if the dll is found, a real one. Another option would be to make some simple logger, and rebuild the shim with or w/o using it, based on directives. This is not the desirable approach, because the shim needs to be signed, and I have to instruct the user to make a backup copy of the "real" one, then restore when done, etc., instead of just saving and deleting a dll. I'd appreciate any good suggestion how to approach it, together with links or sample code how to go after this. Cheers

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  • Why is my view controllers view not quadratic?

    - by mystify
    I created an UIViewController subclass, and figured out that the default implementation of -loadView in UIViewController will ignore my frame size settings in a strange way. To simplify it and to make sure it's really not the fault of my code, I did a clean test with a plain instance of UIViewController directly, rather than making a subclass. The result is the same. I try to make an exactly quadratic view of 320 x 320, but the view appears like 320 x 200. iPhone OS 3.0, please check this out: UIViewController *ts = [[UIViewController alloc] initWithNibName:nil bundle:nil]; ts.view.frame = CGRectMake(0.0f, 0.0f, 320.0f, 320.0f); ts.view.backgroundColor = [UIColor cyanColor]; [self.view addSubview:ts.view]; like you can see, I do this: 1) Create a UIViewController instance 2) Set the frame of the view to a quadratic dimension of 320 x 320 3) Give it a color, so I can see it 4) Added it as a subview. Now the part, that's even more strange: When I make my own implementation of -loadView, i.e. if I put this code in there like this: - (void)loadView { UIView *v = [[UIView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 320.0f, 320.0f)]; v.backgroundColor = [UIColor cyanColor]; self.view = v; [v release]; } then it looks right. Now lets think about that: In the first example, I do pretty much exactly the same, just that I let UIViewController create the view on it's own, and then take it over in order to change it's frame. Right? So why do I get this strange error? Right now I see no other way of messing around like that to correct this wrong behavior. I did not activate anything like clipsToBounds and there's no other code touching this.

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