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  • Writing a program in C++ and I need help [migrated]

    - by compscinoob
    So I am a new to this. I am trying to write a program with a function double_product(vector< double a, vector< double b) that computes the scalar product of two vectors. The scalar product is $a_{0}b_{0}+a_{1}b_{1}+...a_{n-1}b_{n-1}$. Here is what I have. It is a mess, but I am trying! #include<iostream> #include<vector> using namespace std; class Scalar_product { public: Scalar_product(vector<double> a, vector<bouble> b); }; double scalar_product(vector<double> a, vector<double> b) { double product = 0; for (int i=0; i <=a.size()-1; i++) for (int i=0; i <=b.size()-1; i++) product = product + (a[i])*(b[i]); return product; } int main() { cout << product << endl; return 0; }

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  • Applications: The Mathematics of Movement, Part 3

    - by TechTwaddle
    Previously: Part 1, Part 2 As promised in the previous post, this post will cover two variations of the marble move program. The first one, Infinite Move, keeps the marble moving towards the click point, rebounding it off the screen edges and changing its direction when the user clicks again. The second version, Finite Move, is the same as first except that the marble does not move forever. It moves towards the click point, rebounds off the screen edges and slowly comes to rest. The amount of time that it moves depends on the distance between the click point and marble. Infinite Move This case is simple (actually both cases are simple). In this case all we need is the direction information which is exactly what the unit vector stores. So when the user clicks, you calculate the unit vector towards the click point and then keep updating the marbles position like crazy. And, of course, there is no stop condition. There’s a little more additional code in the bounds checking conditions. Whenever the marble goes off the screen boundaries, we need to reverse its direction.  Here is the code for mouse up event and UpdatePosition() method, //stores the unit vector double unitX = 0, unitY = 0; double speed = 6; //speed times the unit vector double incrX = 0, incrY = 0; private void Form1_MouseUp(object sender, MouseEventArgs e) {     double x = e.X - marble1.x;     double y = e.Y - marble1.y;     //calculate distance between click point and current marble position     double lenSqrd = x * x + y * y;     double len = Math.Sqrt(lenSqrd);     //unit vector along the same direction (from marble towards click point)     unitX = x / len;     unitY = y / len;     timer1.Enabled = true; } private void UpdatePosition() {     //amount by which to increment marble position     incrX = speed * unitX;     incrY = speed * unitY;     marble1.x += incrX;     marble1.y += incrY;     //check for bounds     if ((int)marble1.x < MinX + marbleWidth / 2)     {         marble1.x = MinX + marbleWidth / 2;         unitX *= -1;     }     else if ((int)marble1.x > (MaxX - marbleWidth / 2))     {         marble1.x = MaxX - marbleWidth / 2;         unitX *= -1;     }     if ((int)marble1.y < MinY + marbleHeight / 2)     {         marble1.y = MinY + marbleHeight / 2;         unitY *= -1;     }     else if ((int)marble1.y > (MaxY - marbleHeight / 2))     {         marble1.y = MaxY - marbleHeight / 2;         unitY *= -1;     } } So whenever the user clicks we calculate the unit vector along that direction and also the amount by which the marble position needs to be incremented. The speed in this case is fixed at 6. You can experiment with different values. And under bounds checking, whenever the marble position goes out of bounds along the x or y direction we reverse the direction of the unit vector along that direction. Here’s a video of it running;   Finite Move The code for finite move is almost exactly same as that of Infinite Move, except for the difference that the speed is not fixed and there is an end condition, so the marble comes to rest after a while. Code follows, //unit vector along the direction of click point double unitX = 0, unitY = 0; //speed of the marble double speed = 0; private void Form1_MouseUp(object sender, MouseEventArgs e) {     double x = 0, y = 0;     double lengthSqrd = 0, length = 0;     x = e.X - marble1.x;     y = e.Y - marble1.y;     lengthSqrd = x * x + y * y;     //length in pixels (between click point and current marble pos)     length = Math.Sqrt(lengthSqrd);     //unit vector along the same direction as vector(x, y)     unitX = x / length;     unitY = y / length;     speed = length / 12;     timer1.Enabled = true; } private void UpdatePosition() {     marble1.x += speed * unitX;     marble1.y += speed * unitY;     //check for bounds     if ((int)marble1.x < MinX + marbleWidth / 2)     {         marble1.x = MinX + marbleWidth / 2;         unitX *= -1;     }     else if ((int)marble1.x > (MaxX - marbleWidth / 2))     {         marble1.x = MaxX - marbleWidth / 2;         unitX *= -1;     }     if ((int)marble1.y < MinY + marbleHeight / 2)     {         marble1.y = MinY + marbleHeight / 2;         unitY *= -1;     }     else if ((int)marble1.y > (MaxY - marbleHeight / 2))     {         marble1.y = MaxY - marbleHeight / 2;         unitY *= -1;     }     //reduce speed by 3% in every loop     speed = speed * 0.97f;     if ((int)speed <= 0)     {         timer1.Enabled = false;     } } So the only difference is that the speed is calculated as a function of length when the mouse up event occurs. Again, this can be experimented with. Bounds checking is same as before. In the update and draw cycle, we reduce the speed by 3% in every cycle. Since speed is calculated as a function of length, speed = length/12, the amount of time it takes speed to reach zero is directly proportional to length. Note that the speed is in ‘pixels per 40ms’ because the timeout value of the timer is 40ms.  The readability can be improved by representing speed in ‘pixels per second’. This would require you to add some more calculations to the code, which I leave out as an exercise. Here’s a video of this second version,

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  • Is locking on the requested object a bad idea?

    - by Quick Joe Smith
    Most advice on thread safety involves some variation of the following pattern: public class Thing { private static readonly object padlock = new object(); private string stuff, andNonsense; public string Stuff { get { lock (Thing.padlock) { if (this.stuff == null) this.stuff = "Threadsafe!"; } return this.stuff; } } public string AndNonsense { get { lock (Thing.padlock) { if (this.andNonsense == null) this.andNonsense = "Also threadsafe!"; } return this.andNonsense; } } // Rest of class... } In cases where the get operations are expensive and unrelated, a single locking object is unsuitable because a call to Stuff would block all calls to AndNonsense, degrading performance. And rather than create a lock object for each call, wouldn't it be better to acquire the lock on the member itself (assuming it is not something that implements SyncRoot or somesuch for that purpose? For example: public string Stuff { get { lock (this.stuff) { // Pretend that this is a very expensive operation. if (this.stuff == null) this.stuff = "Still threadsafe and good?"; } return this.stuff; } } Strangely, I have never seen this approach recommended or warned against. Am I missing something obvious?

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  • Computer locking up, looking for bootable hardware diagnostic tool.

    - by Carl Menke
    Well today I helped my friend build a computer. All went pretty well until we got to installing Win7. Thing is, we thought, it was crashing constantly. I adjusted pretty much every setting in the BIOS and removed as much hardware as possible to try and prevent a crash. No dice. So far I've tried running an Ubuntu live cd without the harddrive installed. Nope, crashed on boot. And then I just tried Microsoft's ram utility disk and it eventually locked up on that (the ram passed though). So it seems to me like it's either the CPU (AMD PhenomII x3) or the motherboard that could be bad, but I don't know how to test them individually for problems. I thought it could be a overheating issue, but the BIOS reports that the CPU temp is fine idling around 34C. Any advice or diagnostic disk that could help me out? TL;DR: Computer locks up frequently during use (cannot even boot/install an operating system), memory is fine, probably CPU or Mobo, BIOS says CPU temps are fine. What should I try?

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  • Why are my Google and Bing search result pages locking up?

    - by Cyberherbalist
    I've got some really weird behavior going on. I can't do any web searching using Google or Bing because when the search result page shows up, every single link on the page is completely unresponsive. That is, every link to a search result. The links to page functions other than search results work fine. This happens in both IE9 and FF13. It doesn't happen to Yahoo! results, though. Any ideas?

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  • Locking down firmware to keep stolen laptop from being formatted?

    - by Matt Ridge
    On the Mac laptops there are ways through the terminal to lock down the computer so that if someone tries to format the computer they won't be able to do it without the password. This way locks down the firmware. Is there a universal way to do the same thing on a PC? I know there are brands out there such as Samsung, Dell, etc that utilize different fimware types, and in turn will mean that their firmware will be locked down differently. That being said is there a "command code" that will allow you to lock the firmware to keep theives from formatting the hard drive and wiping out your data? I know a person who has time, and knowledge can get any password, and hopefully the person is smart enough to use another password to lock down the firmware, but that's not what I'm asking. I'm asking if it's possible, and if so how? Does the standard PC user require a 3rd party app, or can it be done through the command line? Or Terminal if you are on Linux?

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  • What is the best way to determine what's locking up SQL Server using a query?

    - by Aplato
    Recently our SQL Server is getting bogged down by something. I was wondering what is the best way to check what could be causing the problem by querying the database. This is the best I've found so far: SELECT SPID = s.spid , BlockingSPID = s.blocked , DatabaseName = DB_NAME(s.dbid) , ProgramName = s.program_name , [Status] = s.[status] , LoginName = s.loginame , ObjectName = OBJECT_NAME(objectid, s.dbid) , [Definition] = CAST([text] AS VARCHAR(MAX)) FROM sys.sysprocesses s CROSS APPLY sys.dm_exec_sql_text (sql_handle) WHERE s.spid > 50 ORDER BY DatabaseName , loginName

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  • unexpected behaviour of Ctrl-a x and Ctrl-a X in screen?! regions, locking

    - by gojira
    According to the screen manual (version 4.0.2.) C-a x C-a C-x (lockscreen) Lock this terminal. C-a X (remove) Kill the current region. But what actually happens when I use it (Screen version 4.00.03 (FAU) 23-Oct-06): C-a X locks the terminal and asks me for the password. When I enter the correct passwword, I am back in screen but the region is killed (wtf) C-a x does nothing apparently Please note the differences between x (lowercase) and X (uppercase). Why is there a mixup between the functionalities of C-a X and C-a x? How can I fix this? I am on CentOS release 5 (Final).

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  • Prevent the "System" process from locking my files in a shared folder.

    - by Kamarey
    I have an application that creates files to be processed by SQL bulk. The files are created in shared folder on another server and than taken from there by SQL. The problem that sometime SQL returns an error, that the file is locked by another process and can't be accessed. The process that locks these files is "System" process. Looks like it lock files because of they are in a shared folder, but not sure. The use of any software to unlock files manually is not an option, as all bulk process is automatic. The question is: Why the "System" process locks these files and is there a way to prevent this?

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  • jQuery - upgrade from version 1.6.x to 1.7

    - by Renso
    Goal: Issues to consider when upgrading from jQuery version 1.6 to 1.7. This is a short list and may help identify the real issues you need to concern yourself with in stead of reading through all the release notesSummary of issues encountered during upgrade:As you prepare for upgrade to jQuery 1.7 from 1.6.x, this is a quick glimpse of all the issues that are relevant, not sure if it covers all but may be all you need to worry about.Use this method only for checking checkboxes and radio buttons:$("input:checked")http://api.jquery.com/checked-selector/This will work regardless of the version of jQuery you are using. Note that $("input).attr("checked") returns true prior to jQuery 1.6. Only retrieve "real" attributes with "attr", in order versions it would also retrieve properties like "tagName", this no longer works with jQuery 1.6.1+Why does $("input").attr("checked") no longer (from version 1.6.1+) return TRUE or FALSE, because if you look at the HTML (as well as W3C spec) it does not contain a true/false, but the value checked="checked", which is what it should have returned in the first place. $("input").prop("checked") works, return true, because there is in fact a DOM property for "checked" with the value being "true" or "false".Furthermore, if you want to upgrade to jQuery 1.7 you should only have to worry about this for most part:1. isNumeric() is new, be careful as the older version jQuery.isNaN() has been deprecated2. jqXHR success and error have been deprecated3. When rendering content with text(), white space issue cross-browsers: http://bugs.jquery.com/ticket/3144Other than the issues above I am not aware of any deprecations you need to worry about.Hope this helps to get everyone up to version 1.7

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  • Check if a String is a double or an int?

    - by user69514
    I have a string for a Date in the form mm/dd, and I need to check if either the month or day was entered as a double public Date(String dateStr){ int slash = 0; //check slash is present try{ slash = dateStr.indexOf('/'); }catch(StringIndexOutOfBoundsException e){ error = "Invalid date format: " + dateStr; } //check if month is a number try{ month = Integer.parseInt(dateStr.substring(0, slash)); //day = Integer.parseInt(dateStr.substring(slash + 1, dateStr.length())); } catch(NumberFormatException e){ System.out.println("Invalid format for input string: " + dateStr.substring(0, slash)); } //check if day is a number try{ day = Integer.parseInt(dateStr.substring(slash + 1, dateStr.length())); } catch(NumberFormatException e){ System.out.println("Invalid format for input string: " + dateStr.substring(slash + 1, dateStr.length())); } //check if month was entered as a double }

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  • Why we used double and triple pointer in objective-C or C language?

    - by Rajendra Bhole
    Hi, I confused when i want to take single pointer and when should i take double pointer? In following structure what exactly did? struct objc_class { Class isa; Class super_class; const char *name; long version; long info; long instance_size; struct objc_ivar_list *ivars; struct objc_method_list **methodLists; struct objc_cache *cache; struct objc_protocol_list *protocols; }; Why we use the "**methodLists" double pointer. Edited int sqlite3_get_table( sqlite3 *db, const char zSql, char **pazResult, int *pnRow, int *pnColumn, char *pzErrmsg ); In above scenario what will be meaning of triple pointer char **pazResult?

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  • SQL Server 2005 stored procedure error

    - by user1670625
    I have created a stored procedure of insert command for employee details in SQL Server 2005 in which one of the parameters is an image for which I have used varbinary as the datatype in the table.. But when I am adding that parameter in the stored procedure I am getting the following error- Implicit conversion from data type varchar to varbinary is not allowed. Use the CONVERT function to run this query. Stored procedure: ( @Employee_ID nvarchar(10)='', @Password nvarchar(10)='', @Security_Question nvarchar(50)='', @Answer nvarchar(50)='', @First_Name nvarchar(20)='', @Middle_Name nvarchar(20)='', @Last_Name nvarchar(20)='', @Employee_Type nvarchar(15)='', @Department nvarchar(15)='', @Photo varbinary(50)='' ) insert into Registration ( Employee_ID, Password, Security_Question, Answer, First_Name, Middle_Name, Last_Name, Employee_Type, Department, Photo ) values ( @Employee_ID, @Password, @Security_Question, @Answer, @First_Name, @Middle_Name, @Last_Name, @Employee_Type, @Department, @Photo ) Table structure: Column Name Data Type Allow Nulls Employee_ID nvarchar(10) Unchecked Password nvarchar(10) Checked Security_Question nvarchar(50) Checked Answer nvarchar(50) Checked First_Name nvarchar(20) Checked Middle_Name nvarchar(20) Checked Last_Name nvarchar(20) Checked Employee_Type nvarchar(15) Checked Department nvarchar(15) Checked Photo varbinary(50) Checked I am not getting what to do..can anyone give me some suggestion or solution? Thanks in advance.

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  • Why we used double pointer in objective-C or C language?

    - by Rajendra Bhole
    Hi, I confused when i want to take single pointer and when should i take double pointer? In following structure what exactly did? struct objc_class { Class isa; Class super_class; const char *name; long version; long info; long instance_size; struct objc_ivar_list *ivars; struct objc_method_list **methodLists; struct objc_cache *cache; struct objc_protocol_list *protocols; }; Why we use the "**methodLists" double pointer?

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  • Double data entry system using Infopath 2007 how to compare 2 infopath documents for differences ?

    - by bugBurger
    How to compare 2 infopath documents craeted using double data entry system for differences ? We have a small project contains few infopath forms. Client is using double data entry system to reduce the errors. We are maintaining entry number in infopath form to seperate each entry. Note: I know we can compare xml data files of 2 documents. (xml data file has field names like field1,field2 and so on..while on form that field1 represent some meaninngful text) But the question is we want to compare it Visually side by side. Any difference should highlight the field.

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  • Why am I losing precision when populating an NSDecimalNumber with a double?

    - by Mike
    Here is a simple code that shows what I think is a bug when dealing with double numbers... double wtf = 36.76662445068359375000; id xxx = [NSDecimalNumber numberWithDouble: wtf]; NSString *myBug = [xxx stringValue]; NSLog(@"%.20f", wtf); NSLog(@"%@", myBug); NSLog(@"-------\n"); the terminal will show two different numbers 36.76662445068359375000 and 36.76662445068359168 Is this a bug or am I missing something? if the second number is being rounded, it is a very strange rounding btw...

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  • Enable Disable JQuery Drag-able

    - by jafar201
    Hi all I am working on a print form that will enable Admin user Change the lay out of the print form so i select JQuery Dragable for the job and its working fine but their is one problem when Enable or Disable the first Element in HTML that is dragable take the Disable Style when Dragable is Disabled the other element keep there original look I am using IE 8 . I run the code on Fierfox and Chrome and the result was that all the Element change their style to disable style. I need the Elemnet to Keep there original Stayl <%@ Control Language="C#" AutoEventWireup="true" CodeBehind="PrintablePassportDesigner.ascx.cs" Inherits="CSPDPassportPrintingPOC.UserControls.PrintablePassportDesigner" % function EnableDragAndDrop(cBox) { $("#divDoB").draggable({ disabled: cBox.checked }); $("#divNationalNo").draggable({ disabled: cBox.checked }); $("#divSex").draggable({ disabled: cBox.checked }); $("#divPlaceOfBirth").draggable({ disabled: cBox.checked }); $("#divIssueDate").draggable({ disabled: cBox.checked }); $("#divMotherName").draggable({ disabled: cBox.checked }); $("#divExpDate").draggable({ disabled: cBox.checked }); $("#divAuthority").draggable({ disabled: cBox.checked }); $("#divPassportHolderName").draggable({ disabled: cBox.checked }); }

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  • EXCEL - Locking a Cell from User input whilst allowing a Linked combobox?

    - by Christopher Leach
    I have a Protected Worksheet which is a checklist with a series of checkpoints. Each row has Item and Description cells that are locked. Each row has several columns with its contents to be set by a ComboBox and a text input column. Both i have left unlocked. I have Locked the the Item and Description columns and left only the 'Select Unlocked Cells' checked via Sheet Protection. I have one ComboBox on the worksheet that moves around and adjusts its LinkedCell and its Content list using the worksheets SelectionChanged event. When the user selects a cell to bring up the drop down list, the user is able to type into the cell and the Drop Down Box disappears. What is the best way to keep the cell unlocked so it can be selectable(as 'Select Locked Cells" is unchecked) however stop the user from being able to type in the cell and to allow the cells contents to become modifiable only via the ComboBox?

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  • How do I prevent buffer overflow converting a double to char?

    - by Tommy
    I'm converting a double to a char string: char txt[10]; double num; num = 45.344322345 sprintf(txt, "%.1f", num); and using ".1f" to truncate the decimal places, to the tenths digit. i.e. - txt contains 45.3 I usually use precision in sprintf to ensure the char buffer is not overflowed. How can I do that here also truncating the decimal, without using snprintf? (i.e. if num = 345694876345.3 for some reason) Thanks

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  • How can I get a nstableview to send an action when the user double-clicks an editable cell

    - by overcyn
    I am trying to emulate the behavior found in finder and itunes. Single click on a selected object edits it. Double click opens the object. I have set the doubleAction of the tableView but like it says in the documentation. "If the double-clicked cell is editable, this message isn’t sent and the cell is edited instead." I dont want this. Is there a way i can get that message sent even if the cell is editable? I really have no idea how to begin implementing this. Any general pointers would be appreciated.

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  • Is there any way to disable the "double-click to copy" functionality of a .NET label?

    - by DavidCarroll
    This is really annoying. I'm using the label as part of a list item user control, where the user can click it to select the list item and double-click it to rename it. However, if you had a name in the clipboard, double-clicking the label will replace it with the text of the label! I've also check the other labels in the application, and they will also copy to the clipboard on a doubleclick. I have not written any clipboard code in this program, and I am using the standard .NET labels. Is there any way to disable this functionality?

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  • cocoa - I've discovered what I think is a bug with double numbers...

    - by Mike
    Here is a simple code that shows what I think is a bug when dealing with double numbers... double wtf = 36.76662445068359375000; id xxx = [NSDecimalNumber numberWithDouble: wtf]; NSString *myBug = [xxx stringValue]; NSLog(@"%.20f", wtf); NSLog(@"%@", myBug); NSLog(@"-------\n"); the terminal will show two different numbers 36.76662445068359375000 and 36.76662445068359168 Is this a bug or am I missing something? if the second number is being rounded, it is a very strange rounding btw...

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  • Java generic function for performing calculations on integer, on double?

    - by Daniel
    Is this possible? Surely if you passed in a double, any sort of function implementation code which casts an object to an Integer would not be able to work unless the cast 'Integer' was specifically used? I have a function like: public static void increment(Object o){ Integer one = (Integer)o; system.out.println(one++); } I cant see how this could be made generic for a double? I tried public static <E> void increment(E obj){ E one = (E)o; system.out.println(one++); } but it didn't like it?

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