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• How to implement Horner's scheme for multivariate polynomials?

  - by gsreynolds

  Background I need to solve polynomials in multiple variables using Horner's scheme in Fortran90/95. The main reason for doing this is the increased efficiency and accuracy that occurs when using Horner's scheme to evaluate polynomials. I currently have an implementation of Horner's scheme for univariate/single variable polynomials. However, developing a function to evaluate multivariate polynomials using Horner's scheme is proving to be beyond me. An example bivariate polynomial would be: 12x^2y^2+8x^2y+6xy^2+4xy+2x+2y which would factorised to x(x(y(12y+8))+y(6y+4)+2)+2y and then evaluated for particular values of x & y. Research I've done my research and found a number of papers such as: staff.ustc.edu.cn/~xinmao/ISSAC05/pages/bulletins/articles/147/hornercorrected.pdf citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.40.8637&rep=rep1&type=pdf www.is.titech.ac.jp/~kojima/articles/B-433.pdf Problem However, I'm not a mathematician or computer scientist, so I'm having trouble with the mathematics used to convey the algorithms and ideas. As far as I can tell the basic strategy is to turn a multivariate polynomial into separate univariate polynomials and compute it that way. Can anyone help me? If anyone could help me turn the algorithms into pseudo-code that I can implement into Fortran myself, I would be very grateful.

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• What's the best way to resolve this scope problem?

  - by Peter Stewart

  I'm writing a program in python that uses genetic techniques to optimize expressions. Constructing and evaluating the expression tree is the time consumer as it can happen billions of times per run. So I thought I'd learn enough c++ to write it and then incorporate it in python using cython or ctypes. I've done some searching on stackoverflow and learned a lot. This code compiles, but leaves the pointers dangling. I tried 'this_node = new Node(...' . It didn't seem to work. And I'm not at all sure how I'd delete all the references as there would be hundreds. I'd like to use variables that stay in scope, but maybe that's not the c++ way. What is the c++ way? class Node { public: char *cargo; int depth; Node *left; Node *right; } Node make_tree(int depth) { depth--; if(depth <= 0) { Node tthis_node("value",depth,NULL,NULL); return tthis_node; } else { Node this_node("operator" depth, &make_tree(depth), &make_tree(depth)); return this_node; } };

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• Why is this attempt at a binary search crashing?

  - by Ian Campbell

  I am fairly new to the concept of a binary search, and am trying to write a program that does this in Java for personal practice. I understand the concept of this well, but my code is not working. There is a run-time exception happening in my code that just caused Eclipse, and then my computer, to crash... there are no compile-time errors here though. Here is what I have so far: public class BinarySearch { // instance variables int[] arr; int iterations; // constructor public BinarySearch(int[] arr) { this.arr = arr; iterations = 0; } // instance method public int findTarget(int targ, int[] sorted) { int firstIndex = 1; int lastIndex = sorted.length; int middleIndex = (firstIndex + lastIndex) / 2; int result = sorted[middleIndex - 1]; while(result != targ) { if(result > targ) { firstIndex = middleIndex + 1; middleIndex = (firstIndex + lastIndex) / 2; result = sorted[middleIndex - 1]; iterations++; } else { lastIndex = middleIndex + 1; middleIndex = (firstIndex + lastIndex) / 2; result = sorted[middleIndex - 1]; iterations++; } } return result; } // main method public static void main(String[] args) { int[] sortedArr = new int[] { 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29 }; BinarySearch obj = new BinarySearch(sortedArr); int target = sortedArr[8]; int result = obj.findTarget(target, sortedArr); System.out.println("The original target was -- " + target + ".\n" + "The result found was -- " + result + ".\n" + "This took " + obj.iterations + " iterations to find."); } // end of main method } // end of class BinarySearch

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• how to play an audio soundclip when a nib is loaded - welcome screen - xcode

  - by Pavan

  I would like to do the following two things: 1) I would like to play an audio file qhen a nib is loaded 2) After that i would like to switch views when the audio file has finished playing. This will be easy as i just need to call the event that initiates the change of view by using the delegate method -(void) audioPlayerDidFinishPlaying{ //code to change view } I dont know how to to play the audio file when a nib is loaded. Using the AVFoundation framework, I tried doing the following after setting up the audio player and the variables associated with it in the appropriate places i wrote the following: - (void)viewDidLoad { [super viewDidLoad]; NSString *soundFilePath = [[NSBundle mainBundle] pathForResource: @"sound" ofType: @"mp3"]; NSURL *fileURL = [[NSURL alloc] initFileURLWithPath: soundFilePath]; AVAudioPlayer *newPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL: fileURL error:nil]; [fileURL release]; self.player = newPlayer; [newPlayer release]; [player prepareToPlay]; [player setDelegate: self]; [player play]; } Although this does not play the file as the viewdidload method gets called before the nib is shown so the audio is never played or heard. What do i need to do so that i can play the audio file AFTER the nib has loaded and is shown on the screen? can someone please help me as ive been working on this for 3 hours now. Thanks in advance.

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• How to find/extract data from xml with jQuery

  - by darryl

  I'm trying to extract the StateLongName and StateShortName values from the xml below. I know there has to be a simple elegant way to do this with jQuery. <NewDataSet> <Table> <StateLongName>Alabama</StateLongName> <StateShortName>AL</StateShortName> </Table> <Table> <StateLongName>Alaska</StateLongName> <StateShortName>AK</StateShortName> </Table> ...elments removed for brevity </NewDataSet> Here's what I've tried. Load the xml from above into a Javascript variable name xml. Try #1 $(xml).find("TABLE").each(function() { var stateName = $(this).find("StateLongName").innerText; var stateCode = $(this).find("StateShortName").innerText; }); Try #1 doesn't find anything and never goes inside to load the stateName and stateCode variables. Try #2 $(xml).find("StateLongName").each(function() { var stateName = $(this).find("StateLongName").innerText; var stateCode = $(this).find("StateShortName").innerText; }); Try #2 does find matches, however the stateName and stateCode are left undefined. Try #3 $(xml).find("StateLongName").each(function() { var stateName = $($(xml).find('StateLongName').parent()[0].innerHTML)[1].data; var stateCode = $($(xml).find('StateLongName').parent()[0].innerHTML)[5].data; }); Try #3 works but there has to be a better way. Please enlighten me. Thanks for you time!

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• Mysqli connection trying with different users

  - by gerardo

  I'm trying to create a PHP class extending mysqli that is capable of connecting with another user if the connection fails. It is probably easier to explain with code: public function __construct() { $users = new ArrayObject(self::$user); $passwords = new ArrayObject(self::$pass); $itUser = $users->getIterator(); $itPass = $passwords->getIterator(); parent::__construct(self::$host, $itUser->current(), $itPass->current(), self::$prefix.self::$db); while($this->connect_errno && $itUser->valid()){ $itUser->next(); $itPass->next(); $this->change_user($itUser->current(), $itPass->current(), self::$prefix.self::$db); } if($this->connect_errno) throw new Exception("Error", $this->connect_errno); } $user and $pass are static variables containing arrays of users and passwords. If the first user fails to connect, I try with the next one. The problem here is with $this->connect_errno. It says it cannot find Mysqli. Is there any solution to this or should I create a Factory class?

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• OpenMP - running things in parallel and some in sequence within them

  - by Sayan Ghosh

  Hi, I have a scenario like: for (i = 0; i < n; i++) { for (j = 0; j < m; j++) { for (k = 0; k < x; k++) { val = 2*i + j + 4*k if (val != 0) { for(t = 0; t < l; t++) { someFunction((i + t) + someFunction(j + t) + k*t) } } } } } Considering this is block A, Now I have two more similar blocks in my code. I want to put them in parallel, so I used OpenMP pragmas. However I am not able to parallelize it, because I am a tad confused that which variables would be shared and private in this case. If the function call in the inner loop was an operation like sum += x, then I could have added a reduction clause. In general, how would one approach parallelizing a code using OpenMP, when we there is a nested for loop, and then another inner for loop doing the main operation. I tried declaring a parallel region, and then simply putting pragma fors before the blocks, but definitely I am missing a point there! Thanks, Sayan

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• .NET multithreading, volatile and memory model

  - by fedor-serdukov

  Assume that we have the following code: class Program { static volatile bool flag1; static volatile bool flag2; static volatile int val; static void Main(string[] args) { for (int i = 0; i < 10000 * 10000; i++) { if (i % 500000 == 0) { Console.WriteLine("{0:#,0}",i); } flag1 = false; flag2 = false; val = 0; Parallel.Invoke(A1, A2); if (val == 0) throw new Exception(string.Format("{0:#,0}: {1}, {2}", i, flag1, flag2)); } } static void A1() { flag2 = true; if (flag1) val = 1; } static void A2() { flag1 = true; if (flag2) val = 2; } } } It's fault! The main quastion is Why... I suppose that CPU reorder operations with flag1 = true; and if(flag2) statement, but variables flag1 and flag2 marked as volatile fields...

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• Is it possible to prevent out-of-order execution by using single volatile

  - by Yan Cheng CHEOK

  By referring article, it is using a pair of volatile to prevent out-of-order execution. I was wondering, is it possible to prevent it using single volatile? void fun_by_thread_1() { this.isNuclearFactory = true; this.factory = new NuclearFactory(); } void fun_by_thread_2() { Factory _factory = this.factory; if (this.isNuclearFactory) { // Do not operate nuclear factory!!! return; } // If out-of-order execution happens, _factory might // be NuclearFactory instance. _factory.operate(); } Factory factory = new FoodFactory(); volatile boolean isNuclearFactory = false; The reason I ask, is because I have a single guard flag (similar to isNuclearFactory flag), to guard against multiple variables (similar to many Factory). I do not wish to mark all the Factory as volatile. Or, shall I fall into the following solution? void fun_by_thread_1() { try { writer.lock(); this.isNuclearFactory = true; this.factory = new NuclearFactory(); } finally { writer.unlock(); } } void fun_by_thread_2() { try { reader.lock(); Factory _factory = this.factory; if (this.isNuclearFactory) { // Do not operate nuclear factory!!! return; } } finally { reader.unlock(); } _factory.operate(); } Factory factory = new FoodFactory(); boolean isNuclearFactory = false; P/S: I know instanceof. Factory is just an example to demonstrate of out-of-order problem.

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• Wrappers of primitive types in arraylist vs arrays

  - by ismail marmoush

  Hi, In "Core java 1" I've read CAUTION: An ArrayList is far less efficient than an int[] array because each value is separately wrapped inside an object. You would only want to use this construct for small collections when programmer convenience is more important than efficiency. But in my software I've already used Arraylist instead of normal arrays due to some requirements, though "The software is supposed to have high performance and after I've read the quoted text I started to panic!" one thing I can change is changing double variables to Double so as to prevent auto boxing and I don't know if that is worth it or not, in next sample algorithm public void multiply(final double val) { final int rows = getSize1(); final int cols = getSize2(); for (int i = 0; i < rows; i++) { for (int j = 0; j < cols; j++) { this.get(i).set(j, this.get(i).get(j) * val); } } } My question is does changing double to Double makes a difference ? or that's a micro optimizing that won't affect anything ? keep in mind I might be using large matrices.2nd Should I consider redesigning the whole program again ?

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• Maven: properties not being substituted

  - by jobrahms

  I'm using a maven plugin for install4j in my project, located here. That plugin lets you pass variables to install4j using the <compilerVariables> section. Here's the relevant section of my pom: <plugin> <groupId>com.google.code.maven-install4j</groupId> <artifactId>maven-install4j-plugin</artifactId> <version>0.1.1</version> <configuration> <executable>${devenv.install4jc}</executable> <configFile>${basedir}/newinstaller/ehd.install4j</configFile> <releaseId>${project.version}</releaseId> <attach>false</attach> <skipOnMissingExecutable>false</skipOnMissingExecutable> <compilerVariables> <property> <name>m2_home</name> <value>${settings.localRepository}</value> </property> </compilerVariables> </configuration> </plugin> The problem is that ${settings.localRepository} is not being substituted with the actual directory when I run the plugin. Here's the command line script that install4j is generating: [INFO] Running the following command for install4j compile: /bin/sh -c /home/zach/install4j/bin/install4jc --release=9.1-SNAPSHOT --destination="/home/zach/projects/java/ehdtrunk/target/install4j" -D m2_home=${settings.localRepository} /home/zach/projects/java/ehdtrunk/newinstaller/ehd.install4j Is this the fault of the plugin? If so, what needs to change to allow the substitution to happen?

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• ADODB.Connection undefined

  - by Wes Groleau

  Reference http://stackoverflow.com/questions/1690622/excel-vba-to-sql-server-without-ssis After I got the above working, I copied all the global variables/constants from the routine, which included Const CS As String = "Driver={SQL Server};" _ & "Server=**;" _ & "Database=**;" _ & "UID=**;" _ & "PWD=**" Dim DB_Conn As ADODB.Connection Dim Command As ADODB.Command Dim DB_Status As Stringinto a similar module in another spreadsheet. I also copied Sub Connect_To_Lockbox() If DB_Status < "Open" Then Set DB_Conn = New Connection DB_Conn.ConnectionString = CS DB_Conn.Open ' problem! DB_Status = "Open" End If End SubI added the same reference (ADO 2.8) The first spreadsheet still works; the seccond at DB_Conn.Open pops up "Run-time error '-214767259 (80004005)': [Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified" Removing the references on both, saving files, re-opening, re-adding the references doesn't help. The one still works and the other gets the error. ?!?

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• Pointing to array element

  - by regular

  What I'm trying to achieve is say i have an array, i want to be able to modify a specific array element throughout my code, by pointing at it. for example in C++ i can do this int main(){ int arr [5]= {1,2,3,4,5}; int *c = &arr[3]; cout << arr[3] <<endl; *c = 0; cout << arr[3]<<endl; } I did some googling and there seems to be a way to do it through 'unsafe', but i don't really want to go that route. I guess i could create a variable to store the indexes, but I'm actually dealing with slightly more complexity (a list within a list. so having two index variables seems to add complexity to the code.) C# has a databinding class, so what I'm currently doing is binding the array element to a textbox (that i have hidden) and modifying that textbox whenever i want to modify the specific array element, but that's also not a good solution (since i have a textbox that's not being used for its intended purpose - a bit misleading).

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• Template compiling errors on iPhone SDK 3.2

  - by Didier Malenfant

  I'm porting over some templated code from Windows and I'm hitting some compiler differences on the iPhone 3.2 SDK. Original code inside a class template's member function is: return BinarySearch<uint32, CSimpleKey<T> >(key); where BinarySearch is a method inherited from another template. This produces the following error: csimplekeytable.h:131: error: no matching function for call to 'BinarySearch(NEngine::uint32&)' The visual studio compiler seems to walk up the template hierarchy fine but gcc needs me to fully qualify where the function comes from (I have verified this by fixing the same issues with template member variables that way). So I now need to change this into: return CSimpleTable<CSimpleKey<T> >::BinarySearch<uint32, CSimpleKey<T> >(key); Which now produces the following error: csimplekeytable.h:132: error: expected primary-expression before ',' token csimplekeytable.h:132: error: expected primary-expression before '>' token After some head scratching, I believe what's going on here is that it's trying to resolve the '<' before BinarySearch as a 'Less Than' operator for some reason. So two questions: - Am I on the right path with my interpretation of the error? - How do I fix it? -D

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• Does this language feature already exists?

  - by Pindatjuh

  I'm currently developing a new language for programming in a continuous environment (compare it to electrical engineering), and I've got some ideas on a certain language construction. Let me explain the feature by explanation and then by definition; x = a | b; Where x is a variable and a and b are other variables (or static values). if(x == a) { // all references to "x" are essentially references to "a". } if(x == b) { // same but with "b" } if(x != a) { // ... } if(x == a | b) { // guaranteed that "x" is '"a" | "b"'; interacting with "x" // will interact with both "a" and "b". } // etc. In the above, all code-blocks are executed, but the "scope" changes in each block how x is interpreted. In the first block, x is guaranteed to be a: thus interacting with x inside that block will interact on a. The second and the third code-block are only equal in this situation (because not b only remains a). The last block guarantees that x is at least a or b. Further more; | is not the "bitwise or operator", but I've called it the "and/or"-operator. It's definition is: "|" = "and" | "or" (On my blog, http://cplang.wordpress.com/2009/12/19/binop-and-or/, is more (mathematical) background information on this operator. It's loosely based on sets.) I do not know if this construction already exists, so that's my question: does this language feature already exists?

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• How to show a form field ONLY if another is selected in JavaScript or jQuery?

  - by Sam

  I have a form, like so: <form action="" method="post"> <select name="pageType"> <option value="main">Main Page</option> <option value="sub">Sub Page</option> <option value="sub-sub">Sub-Sub Page</option> </select> <br /> <label>Choose Sub Sub Name:</label> <input type="text" name="sub-sub-name" /> <br /> <input type="submit" name="submit" value="GO!" /> </form> What I would like to achive is for this text field (and it's label): <label>Choose Sub Sub Name:</label> <input type="text" name="sub-sub-name" /> to only appear if the 3rd option (sub sub page) is selected from the drop down and not show up otherwise. How can this be done with either javascript or the jquery framework? EDIT by the way, it would be nice if this can be achieved without the page needing to refresh and losing previously submitted form data. I know form data can still be kept using variables that store the values even on page refresh, but I was hoping for that effect that I see on a lot of sites where the additional text area (or other form element) just appears without page refresh.

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• java generics and the addAll method

  - by neesh

  What is the correct type of argument to the addAll(..) method in Java collections? If I do something like this: Collection<HashMap<String, Object[]>> addAll = new ArrayList<HashMap<String, Object[]>>(); // add some hashmaps to the list.. currentList.addAll(newElements); //currentList is of type: List<? extends Map<String, Object[]>> I understand I need to initialize both variables. However, I get a compilation error (from eclipse): Multiple markers at this line - The method addAll(Collection<? extends capture#1-of ? extends Map<String,Object[]>>) in the type List<capture#1-of ? extends Map<String,Object[]>> is not applicable for the arguments (List<capture#2-of ? extends Map<String,Object[]>>) - The method addAll(Collection<? extends capture#1-of ? extends Map<String,Object[]>>) in the type List<capture#1-of ? extends Map<String,Object[]>> is not applicable for the arguments (Collection<HashMap<String,Object[]>>) what am I doing wrong?

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• In C++, what is the scope resolution ("order of precedence") for shadowed variable names?

  - by Emile Cormier

  In C++, what is the scope resolution ("order of precedence") for shadowed variable names? I can't seem to find a concise answer online. For example: #include <iostream> int shadowed = 1; struct Foo { Foo() : shadowed(2) {} void bar(int shadowed = 3) { std::cout << shadowed << std::endl; // What does this output? { int shadowed = 4; std::cout << shadowed << std::endl; // What does this output? } } int shadowed; }; int main() { Foo().bar(); } I can't think of any other scopes where a variable might conflict. Please let me know if I missed one. What is the order of priority for all four shadow variables when inside the bar member function?

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• Trying to work with a multi-value array in LotusScript and sort of stuck

  - by rrumaner

  I have to find a way to store a series of variables - MonthYear (the key) and a counter. The purpose of this is to track the number of documents processed by Month & Year. I was thinking of a list but I am not sure how to save the data so that it is readable and able to be shown in a table at a later date. I thought about using a multi-dimensional array - someArray(1,0 to 1) and ReDim'ing it each time I start a new MonthYear and then save it back to a field on the document but am not sure how that is going to play out. Does anyone have an idea of how I can accomplish this? The first dimension will be the MonthYear (key) and the second will be a counter that is updated every time a new document is processed. The key will be based on a field on the document being processed. How can I make sure I am updating the right key/counter combination? How can I retrieve the existing counter from the field on the document, update the counter and then replace the value? I thought about just adding a new element (ReDim) every time a document is processed and than somehow adding up all the counters for each key and storing that in an array, but that just seems real messy. There has to be a good way to do this. Any and all ideas will be greatly appreciated

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• C++: select argmax over vector of classes w.r.t. arbitrary expression

  - by karpathy

  Hello, I have trouble describing my problem so I'll give an example: I have a class description that has a couple of variables in it, for example: class A{ float a, b, c, d; } Now, I maintain a vector<A> that contains many of these classes. What I need to do very very often is to find the object inside this vector that satisfies that one of it's parameters is maximal w.r.t to the others. i.e code looks something like: int maxi=-1; float maxa=-1000; for(int i=0;i<vec.size();i++){ res= vec[i].a; if(res > maxa) { maxa= res; maxi=i; } } return vec[maxi]; However, sometimes I need to find class with maximal a, sometimes with maximal b, sometimes the class with maximal 0.8*a + 0.2*b, sometimes I want a maximal a*VAR + b, where VAR is some variable that is assigned in front, etc. In other words, I need to evaluate an expression for every class, and take the max. I find myself copy-pasting this everywhere, and only changing the single line that defines res. What makes it even more complicated is that even the name of the vector changes. Sometimes it's vec, sometimes it can be something else. I have many vectors that contain A's. This could be changed if this makes the problem too hard. Is there some nice way to avoid this insanity in C++? What's the neatest way to handle this? Thank you!

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• implement SIMD in C++

  - by Hristo

  I'm working on a bit of code and I'm trying to optimize it as much as possible, basically get it running under a certain time limit. The following makes the call... static affinity_partitioner ap; parallel_for(blocked_range<size_t>(0, T), LoopBody(score), ap); ... and the following is what is executed. void operator()(const blocked_range<size_t> &r) const { int temp; int i; int j; size_t k; size_t begin = r.begin(); size_t end = r.end(); for(k = begin; k != end; ++k) { // for each trainee temp = 0; for(i = 0; i < N; ++i) { // for each sample int trr = trRating[k][i]; int ei = E[i]; for(j = 0; j < ei; ++j) { // for each expert temp += delta(i, trr, exRating[j][i]); } } myscore[k] = temp; } } I'm using Intel's TBB to optimize this. But I've also been reading about SIMD and SSE2 and things along that nature. So my question is, how do I store the variables (i,j,k) in registers so that they can be accessed faster by the CPU? I think the answer has to do with implementing SSE2 or some variation of it, but I have no idea how to do that. Any ideas? Thanks, Hristo

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• Newbie C# Question about float/int/text type formatting

  - by user563501

  Hey everybody, I'm a total C# newb with a light (first year CS) background in Python. I wrote a console program in Python for doing marathon pace running calculations and I'm trying to figure out the syntax for this in C# using Visual Studio 2010. Here's a chunk of what I've got so far: string total_seconds = ((float.Parse(textBox_Hours.Text) * 60 * 60) + (float.Parse(textBox_Minutes.Text) * 60) + float.Parse(textBox_Seconds.Text)).ToString(); float secs_per_unit = ((float)(total_seconds) / (float)(textBox_Distance.Text)); float mins_per_unit = (secs_per_unit / 60); string pace_mins = (int)mins_per_unit.ToString(); string pace_secs = (float.Parse(mins_per_unit) - int.Parse(mins_per_unit) * 60).ToString(); textBox_Final_Mins.Text = pace_mins; textBox_Final_Secs.Text = pace_mins; Imagine you have a running pace of 8 minutes and 30 seconds per mile. secs_per_unit would be 510, mins_per_unit would be 8.5. pace_mins would simply be 8 and pace_secs would be 30. In Python I'd just convert variables from a float to a string to get 8 instead of 8.5, for example; hopefully the rest of the code gives you an idea of what I've been doing. Any input would be appreciated.

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• InvalidCastException when getting Text from a Label referenced by dynamicaly built String, Fix?

  - by Chris

  NET Version: 3.5 Ok, I recieve an error (System.InvalidCastException was unhandled. Message="Unable to cast object of type 'System.Windows.Forms.Control[]' to type 'System.Windows.Forms.Label'.") when trying to get Text from a Label referenced by a dynamicly built string. Here's my situation; I have an array of 250 labels named l1 - l250. What I want to do is loop through them using this while statement: int c = 1; while (c < 251) { string k = "l" + c.ToString(); //dynamic name of Control(Label) object ka = Controls.Find(k, true); string ct = ((Label)ka).Text; //<<Error Occurs Here build = build + ct; c++; } and get the text value of each to build a string named build. I don't get any build errors, just this while debuging. While debuging I can go down to view my local variables. When looking through these, I can view the contents of object ka; it does contain the correct Text value of the correct Label I want to "access". I just don't understand how to get there. The text value is listed under "[0]" which is the only subcatagory for "ka".

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• ArrayList<String> NullPointerException

  - by Carlucho

  Am trying to solve a labyrinth by DFS, using adj List to represent the vertices and edges of the graph. In total there are 12 nodes (3 rows[A,B,C] * 4 cols[0,..,3]). My program starts by saving all the vertex labels (A0,..C3), so far so good, then checks the adjacent nodes, also no problems, if movement is possible, it proceeds to create the edge, here its where al goes wrong. adjList[i].add(vList[j].label); I used the debugger and found that vList[j].label is not null it contains a correct string (ie. "B1"). The only variables which show null are in adjList[i], which leads me to believe i have implemented it wrongly. this is how i did it. public class GraphList { private ArrayList<String>[] adjList; ... public GraphList(int vertexcount) { adjList = (ArrayList<String>[]) new ArrayList[vertexCount]; ... } ... public void addEdge(int i, int j) { adjList[i].add(vList[j].label); //NULLPOINTEREXCEPTION HERE } ... } I will really appreaciate if anyone can point me on the right track regrading to what its going wrong... Thanks!

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• How to have multiple instances of jQuery plugin on single page?

  - by James Skidmore

  I'm writing a simple jQuery plugin, but I'm having trouble being able to use multiple instances on a page. For instance, here is a sample plugin to illustrate my point: (function($) { $.fn.samplePlugin = function(options) { if (typeof foo != 'undefined') { alert('Already defined!'); } else { var foo = 'bar'; } }; })(jQuery); And then if I do this: $(document).ready(function(){ $('#myDiv').samplePlugin({}); // does nothing $('#myDiv2').samplePlugion({}); // alerts "Already defined!" }); This is obviously an over-simplified example to get across the point. So my question is, how do I have two separate instances of the plugin? I'd like to be able to use it across multiple instances on the same page. I'm guessing that part of the problem might be with defining the variables in a global scope. How can I define them unique to that instance of the plugin then? Thank you for your guidance!

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