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  • Using different languages in one project

    - by Tarbal
    I recently heard about the use of several different languages in a (big) project, I also read about famous services such as Twitter using Rails as frontend, mixed with some other languages, and Scala I think it was as backend. Is this common practice? Who does that? I'm sure there are disadvantages to this. I think that you will have problems with the different interpreters/compilers and seamlessly connecting the different languages. Is this true? Why is this actually done? For performance?

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  • How do I program hardware?

    - by Arlen Beiler
    What would I need to program a piece of hardware to do something for me? Let's say I have something with 15 relays (or equivalent) and I want to tell it to turn off relay 10. Or better yet, when sensor 10 is activated, toggle relay 10.

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  • Using Unix Process Controll Methods in Ruby

    - by John F. Miller
    Ryan Tomayko touched off quite a fire storm with this post about using Unix process control commands. We should be doing more of this. A lot more of this. I'm talking about fork(2), execve(2), pipe(2), socketpair(2), select(2), kill(2), sigaction(2), and so on and so forth. These are our friends. They want so badly just to help us. I have a bit of code (a delayed_job clone for DataMapper that I think would fit right in with this, but I'm not clear on how to take advantage of the listed commands. Any Ideas on how to improve this code? def start say "*** Starting job worker #{@name}" t = Thread.new do loop do delay = Update.work_off(self) break if $exit sleep delay break if $exit end clear_locks end trap('TERM') { terminate_with t } trap('INT') { terminate_with t } trap('USR1') do say "Wakeup Signal Caught" t.run end end

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  • Known "Z notation" applications ?

    - by Amadeus45
    I was just remembering back my university classes and was wondering to know if anyone out here even used the "Z notation" in a professional environment. I honestly must say that it was the single most boring class that I have ever attended in my life. Maybe because of the teacher, but at the time we really all thought it was a big waste of time. I might have been wrong, which is why I'd like to hear you about it. If you are using it or some derived language (Z++), I'd just like to know how is it useful for you. Just curious to know some commonly-known applications of Z or your application. For those who are not familiar : http://staff.washington.edu/jon/z/z-examples.html

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  • Unix Piping using Fork and Dup

    - by Jacob
    Lets say within my program I want to execute two child processes, one to to execute a "ls -al" command and then pipe that into "wc" command and display the output on the terminal. How can I do this using pipe file descriptors so far the code I have written: An example would be greatly helpful int main(int argc, char *argv[]) { int pipefd[2] pipe(pipefd2); if ((fork()) == 0) { dup2(pipefd2[1],STDOUT_FILENO); close(pipefd2[0]); close(pipefd2[1]); execl("ls", "ls","-al", NULL); exit(EXIT_FAILURE); } if ((fork()) == 0){ dup2(pipefd2[0],STDIN_FILENO); close(pipefd2[0]); close(pipefd2[1]); execl("/usr/bin/wc","wc",NULL); exit(EXIT_FAILURE); } close(pipefd[0]); close(pipefd[1]); close(pipefd2[0]); close(pipefd2[1]); }

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  • side effect gotchas in python/numpy? horror stories and narrow escapes wanted

    - by shabbychef
    I am considering moving from Matlab to Python/numpy for data analysis and numerical simulations. I have used Matlab (and SML-NJ) for years, and am very comfortable in the functional environment without side effects (barring I/O), but am a little reluctant about the side effects in Python. Can people share their favorite gotchas regarding side effects, and if possible, how they got around them? As an example, I was a bit surprised when I tried the following code in Python: lofls = [[]] * 4 #an accident waiting to happen! lofls[0].append(7) #not what I was expecting... print lofls #gives [[7], [7], [7], [7]] #instead, I should have done this (I think) lofls = [[] for x in range(4)] lofls[0].append(7) #only appends to the first list print lofls #gives [[7], [], [], []] thanks in advance

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  • Sending series of images to display like a movie on iPhone

    - by unknownthreat
    Allow me to elaborate more. On the server, we will have a program that will take data from iPhone and process that data and produce series of images. Each time an image is generated, it will be send back to display on iPhone. I have done all of the things above using UDP, OpenGL, and such. It works. The images are transferred to iPhone and can be displayed, but it is slow. The image's resolution is around 320 x 420 and we send the image pixels by pixels. This naive implementation leads to a slow framerate. I can see around 2-3 frames per second. There are also some UDP packets dropped, and this is expected. Are there any sort of compression method available for something like this? Are there any other method that can make this better? NOTE: please don't just write "compression" as an answer, because we are aware that we will need to do it in some ways.

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  • Math/numerical formula every computer programmer should know

    - by aaa
    This is a follow-up question to What should every programmer know and Is mathematics necessary. So the question is, as a computer programmer, what is the most important/useful mathematical or numerical formula that you use? By Formula I mean anything that involves less obvious manipulations, whenever binomial coefficients or bit hacks. I work with multidimensional arrays and various matrix representations. So for me most commonly used formulas are: A(i,j,k,..) = a[i + j*Dim0 + k*Dim0*Dim1 + ... to map indexes to one dimension ( which is basic address calculation which many people do not seem to know). And triangular number T(i) = (i*i + i)/2 which is related to binomial coefficients, used to calculate address in triangular matrixes and many other things. What is your workhorse formula that you think programmer should know?

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  • How to handle activity life cycle involving sockets in Android?

    - by Henrik
    Hello all, I have an Android activity which in turn starts a thread. In the thread I open a persistent TCP socket connection. When the socket connects to the server dynamic data is downloaded. The thread sends messages using Handler-class to the activity when data has been received. Now if the user happens to switch from portrait to landscape mode the activity gets an onDestroy call. At this moment I close the socket and stop the thread. When Android has switched landscape mode it calls onCreate yet again and I have to do a socket re-connect. Also, all of the data the activity received needs to be downloaded once more because the server does not have the ability to know what has been sent before, i.e. there is no "resume" feature. Thus the problem is that there is alot of data which is resent all the time when landscape mode is changed. What are my options here? Should I create a service which handles the socket traffic towards the server thus I always got all the data which the server has sent in the service. Or should I disable landscape mode all together perhaps? Or would my best bet be to rewrite my server which is a VERY BIG job :-) All input is welcome :-) / Henrik

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  • What languages have a while-else type control structure, and how does it work?

    - by Dan
    A long time ago, I thought I saw a proposal to add an else clause to for or while loops in C or C++... or something like that. I don't remember how it was supposed to work -- did the else clause run if the loop exited normally but not via a break statement? Anyway, this is tough to search for, so I thought maybe I could get some CW answers here for various languages. What languages support adding an else clause to something other than an if statement? What is the meaning of that clause? One language per answer please.

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  • Errors when connecting to HTTPS using HTTP::Net routines (Ruby on Rails)

    - by jaycode
    Hi all, the code below explains the problem in detail #this returns error Net::HTTPBadResponse url = URI.parse('https://sitename.com') response = Net::HTTP.start(url.host, url.port) {|http| http.get('/remote/register_device') } #this works url = URI.parse('http://sitename.com') response = Net::HTTP.start(url.host, url.port) {|http| http.get('/remote/register_device') } #this returns error Net::HTTPBadResponse response = Net::HTTP.post_form(URI.parse('https://sitename.com/remote/register_device'), {:text => 'hello world'}) #this returns error Errno::ECONNRESET (Connection reset by peer) response = Net::HTTP.post_form(URI.parse('https://sandbox.itunes.apple.com/verifyReceipt'), {:text => 'hello world'}) #this works response = Net::HTTP.post_form(URI.parse('http://sitename.com/remote/register_device'), {:text => 'hello world'}) So... how do I send POST parameters to https://sitename.com or https://sandbox.itunes.apple.com/verifyReceipt in this example? Further information, I am trying to get this working in Rails: http://developer.apple.com/iphone/library/documentation/NetworkingInternet/Conceptual/StoreKitGuide/VerifyingStoreReceipts/VerifyingStoreReceipts.html#//apple_ref/doc/uid/TP40008267-CH104-SW1

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  • Running Network Application on port Server side give me error how can i solve it?

    - by Phsika
    if i run Server App. Exception occurs: on Dinle.Start() System.Net.SocketException - Only one usage of each socket address (protocol/network address/port) is normally permitted How can i solve this error? Server.cs using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.IO; using System.Net; using System.Net.Sockets; using System.Threading; namespace Server { public partial class Server : Form { Thread kanal; public Server() { InitializeComponent(); try { kanal = new Thread(new ThreadStart(Dinle)); kanal.Start(); kanal.Priority = ThreadPriority.Normal; this.Text = "Kanla Çalisti"; } catch (Exception ex) { this.Text = "kanal çalismadi"; MessageBox.Show("hata:" + ex.ToString()); kanal.Abort(); throw; } } private void Server_Load(object sender, EventArgs e) { Dinle(); } private void btn_Listen_Click(object sender, EventArgs e) { Dinle(); } void Dinle() { // IPAddress localAddr = IPAddress.Parse("localhost"); // TcpListener server = new TcpListener(port); // server = new TcpListener(localAddr, port); //TcpListener Dinle = new TcpListener(localAddr,51124); TcpListener Dinle = new TcpListener(51124); try { while (true) { Dinle.Start(); Exception is occured. Socket Baglanti = Dinle.AcceptSocket(); if (!Baglanti.Connected) { MessageBox.Show("Baglanti Yok"); } else { TcpClient tcpClient = Dinle.AcceptTcpClient(); if (tcpClient.ReceiveBufferSize 0) { byte[] Dizi = new byte[250000]; Baglanti.Receive(Dizi, Dizi.Length, 0); string Yol; saveFileDialog1.Title = "Dosyayi kaydet"; saveFileDialog1.ShowDialog(); Yol = saveFileDialog1.FileName; FileStream Dosya = new FileStream(Yol, FileMode.Create); Dosya.Write(Dizi, 0, Dizi.Length - 20); Dosya.Close(); listBox1.Items.Add("dosya indirildi"); listBox1.Items.Add("Dosya Boyutu=" + Dizi.Length.ToString()); listBox1.Items.Add("Indirilme Tarihi=" + DateTime.Now); listBox1.Items.Add("--------------------------------"); } } } } catch (Exception ex) { MessageBox.Show("hata:" + ex.ToString()); } } } }

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  • Naming Suggestions For A Function Providing Chaining In A Different Way

    - by sid3k
    I've coded an experimental function which makes passed objects chainable by using high order functions. It's name is "chain" for now, and here is a usage example; chain("Hello World") (print) // evaluates print function by passing "Hello World" object. (console.log,"Optional","Parameters") (returnfrom) // returns "Hello World" It looks lispy but behaves very different since it's coded in a C based language, I don't know if there is a name for this idiom and I couldn't any name more suitable than "chain". Any ideas, suggestions?

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  • Difference between 'scope' and 'namespace'?

    - by katriel
    What is the difference, in general, between the concepts of namespaces and scope? To my understanding, both describe the parts of a program in which a variable/object/method/function will be accessible. I understand that 'scope' tends to be a property of the variable (e.g., "This variable has global scope"), while a 'namespace' is a property of the program (e.g., "A Python function creates a local namespace"). Are there other differences? Global scope vs global namespace addresses a slightly narrower question: global namespaces in C++. http://www.alan-g.me.uk/tutor/tutname.htm states, There are a few very subtle differences between the terms but only a Computer Scientist pedant would argue with you, and for our purposes namespace and scope are identical. What are those subtle differences? Under what circumstances or with which kinds of languages do people use each concept?

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  • XML RSS to HTML parser doesn't work

    - by mstr
    I'm using MCX (I don't even know if someone here is familiar with it, pretty unkown derivate of COBOL and Fortran, look it up in google when you don't believe me) Note: I'm using MCX on the MCX-WebServices server as it does neither support apache or ISS, mabye that is one problem. The thing is that I want to use the XML library to read in an XML file and convert it into an output format readable by the user. The XML lib already has all the functions I need for that, yet my program fails. #!usr/bin/mcx $PGRM.ID: index.mcx $PGRM.AT: /mstr SHOWERROR: WRITE XML.LastError --> OUTPUT DO_FLUSH xcit end\ MAIN: IMPORT Extras.XML USE Extras $XML_RSS_FILE: XML.ReadIn "rss.xml" ! $XML_RSS_FILE --> GOTO SHOWERROR $XML_RSS: XML.FormatRSS1 <-- $XML_RSS_FILE ! $XML_RSS --> GOTO SHOWERROR WRITE $XML_RSS --> OUTPUT DO_FLUSH FLUSH xcit end\ Program output: Nothing The rss.xml file 100% exists and is readable Thanks in advance

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  • MPAPI vs MPI.NET vs ?

    - by Olexandr
    I'm working on college project. I have to develop distributed computing system. And i decided to do some research to make this task fun :) I've found MPAPI and MPI.NET libraries. Yes, they are .NET libraries(Mono, in my case). Why .NET ? I'm choosing between Ada, C++ and C# so to i've choosed C# because of lower development time. I have two goals: Simplicity; Performance; Cluster computing. So, what to choose - MPAPI or MPI.NET or something else ?

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  • math library in gcc

    - by Betamoo
    I am writing a program on linux gcc... When I tried to include <math.h> I found that I need to link math library by using command gcc -lm But I am searching for another way to link the math library 'in code', that does not require the user to compile using any options.. Can gcc -lm be done in c code using #pragma or something? EDIT: I have changed -ml to -lm

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  • shell script passing arguments

    - by arav
    From the wrapper shell scripts i am calling the Java program. I want the Unix shell script to pass all the arguments to java program except the EMAIL argument. HOW Can i remove the EMAIL argument and pass the rest of the arguments to the java program. EMAIL argument can come at any position. valArgs() { until [ $# -eq 0 ]; do case $1 in -EMAIL) MAILFLAG=Y shift break ;; esac done } main() { valArgs "$@" $JAVA_HOME/bin/java -d64 -jar WEB-INF/lib/test.jar "$@"

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  • parallelizing code using openmp

    - by anubhav
    Hi, The function below contains nested for loops. There are 3 of them. I have given the whole function below for easy understanding. I want to parallelize the code in the innermost for loop as it takes maximum CPU time. Then i can think about outer 2 for loops. I can see dependencies and internal inline functions in the innermost for loop . Can the innermost for loop be rewritten to enable parallelization using openmp pragmas. Please tell how. I am writing just the loop which i am interested in first and then the full function where this loop exists for referance. Interested in parallelizing the loop mentioned below. //* LOOP WHICH I WANT TO PARALLELIZE *// for (y = 0; y < 4; y++) { refptr = PelYline_11 (ref_pic, abs_y++, abs_x, img_height, img_width); LineSadBlk0 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk0 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk0 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk0 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk1 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk1 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk1 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk1 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk2 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk2 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk2 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk2 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk3 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk3 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk3 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk3 += byte_abs [*refptr++ - *orgptr++]; } The full function where this loop exists is below for referance. /*! *********************************************************************** * \brief * Setup the fast search for an macroblock *********************************************************************** */ void SetupFastFullPelSearch (short ref, int list) // <-- reference frame parameter, list0 or 1 { short pmv[2]; pel_t orig_blocks[256], *orgptr=orig_blocks, *refptr, *tem; // created pointer tem int offset_x, offset_y, x, y, range_partly_outside, ref_x, ref_y, pos, abs_x, abs_y, bindex, blky; int LineSadBlk0, LineSadBlk1, LineSadBlk2, LineSadBlk3; int max_width, max_height; int img_width, img_height; StorablePicture *ref_picture; pel_t *ref_pic; int** block_sad = BlockSAD[list][ref][7]; int search_range = max_search_range[list][ref]; int max_pos = (2*search_range+1) * (2*search_range+1); int list_offset = ((img->MbaffFrameFlag)&&(img->mb_data[img->current_mb_nr].mb_field))? img->current_mb_nr%2 ? 4 : 2 : 0; int apply_weights = ( (active_pps->weighted_pred_flag && (img->type == P_SLICE || img->type == SP_SLICE)) || (active_pps->weighted_bipred_idc && (img->type == B_SLICE))); ref_picture = listX[list+list_offset][ref]; //===== Use weighted Reference for ME ==== if (apply_weights && input->UseWeightedReferenceME) ref_pic = ref_picture->imgY_11_w; else ref_pic = ref_picture->imgY_11; max_width = ref_picture->size_x - 17; max_height = ref_picture->size_y - 17; img_width = ref_picture->size_x; img_height = ref_picture->size_y; //===== get search center: predictor of 16x16 block ===== SetMotionVectorPredictor (pmv, enc_picture->ref_idx, enc_picture->mv, ref, list, 0, 0, 16, 16); search_center_x[list][ref] = pmv[0] / 4; search_center_y[list][ref] = pmv[1] / 4; if (!input->rdopt) { //--- correct center so that (0,0) vector is inside --- search_center_x[list][ref] = max(-search_range, min(search_range, search_center_x[list][ref])); search_center_y[list][ref] = max(-search_range, min(search_range, search_center_y[list][ref])); } search_center_x[list][ref] += img->opix_x; search_center_y[list][ref] += img->opix_y; offset_x = search_center_x[list][ref]; offset_y = search_center_y[list][ref]; //===== copy original block for fast access ===== for (y = img->opix_y; y < img->opix_y+16; y++) for (x = img->opix_x; x < img->opix_x+16; x++) *orgptr++ = imgY_org [y][x]; //===== check if whole search range is inside image ===== if (offset_x >= search_range && offset_x <= max_width - search_range && offset_y >= search_range && offset_y <= max_height - search_range ) { range_partly_outside = 0; PelYline_11 = FastLine16Y_11; } else { range_partly_outside = 1; } //===== determine position of (0,0)-vector ===== if (!input->rdopt) { ref_x = img->opix_x - offset_x; ref_y = img->opix_y - offset_y; for (pos = 0; pos < max_pos; pos++) { if (ref_x == spiral_search_x[pos] && ref_y == spiral_search_y[pos]) { pos_00[list][ref] = pos; break; } } } //===== loop over search range (spiral search): get blockwise SAD ===== **// =====THIS IS THE PART WHERE NESTED FOR STARTS=====** for (pos = 0; pos < max_pos; pos++) // OUTERMOST FOR LOOP { abs_y = offset_y + spiral_search_y[pos]; abs_x = offset_x + spiral_search_x[pos]; if (range_partly_outside) { if (abs_y >= 0 && abs_y <= max_height && abs_x >= 0 && abs_x <= max_width ) { PelYline_11 = FastLine16Y_11; } else { PelYline_11 = UMVLine16Y_11; } } orgptr = orig_blocks; bindex = 0; for (blky = 0; blky < 4; blky++) // SECOND FOR LOOP { LineSadBlk0 = LineSadBlk1 = LineSadBlk2 = LineSadBlk3 = 0; for (y = 0; y < 4; y++) //INNERMOST FOR LOOP WHICH I WANT TO PARALLELIZE { refptr = PelYline_11 (ref_pic, abs_y++, abs_x, img_height, img_width); LineSadBlk0 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk0 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk0 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk0 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk1 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk1 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk1 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk1 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk2 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk2 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk2 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk2 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk3 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk3 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk3 += byte_abs [*refptr++ - *orgptr++]; LineSadBlk3 += byte_abs [*refptr++ - *orgptr++]; } block_sad[bindex++][pos] = LineSadBlk0; block_sad[bindex++][pos] = LineSadBlk1; block_sad[bindex++][pos] = LineSadBlk2; block_sad[bindex++][pos] = LineSadBlk3; } } //===== combine SAD's for larger block types ===== SetupLargerBlocks (list, ref, max_pos); //===== set flag marking that search setup have been done ===== search_setup_done[list][ref] = 1; } #endif // _FAST_FULL_ME_

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  • how to maintain multiple components for multiple client for multiple features?

    - by Dhana
    Basically my project is product based. Once we developed a project and catch the multiple client and deploy the application based on their needs. But We decided to put the new features and project dependent modules are as component. Now my application got many number of customer. Every customer needs a different features based on the component. But we have centralized component for all client . we move the components additional feature to client specific folder and deploy. My problem is , I am unable maintain the components features for multiple client. My component feature code is increased and I am unable to track the client features. Is there any solution for maintaining the multiple component features for multiple client ?

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  • More FP-correct way to create an update sql query

    - by James Black
    I am working on access a database using F# and my initial attempt at creating a function to create the update query is flawed. let BuildUserUpdateQuery (oldUser:UserType) (newUser:UserType) = let buf = new System.Text.StringBuilder("UPDATE users SET "); if (oldUser.FirstName.Equals(newUser.FirstName) = false) then buf.Append("SET first_name='").Append(newUser.FirstName).Append("'" ) |> ignore if (oldUser.LastName.Equals(newUser.LastName) = false) then buf.Append("SET last_name='").Append(newUser.LastName).Append("'" ) |> ignore if (oldUser.UserName.Equals(newUser.UserName) = false) then buf.Append("SET username='").Append(newUser.UserName).Append("'" ) |> ignore buf.Append(" WHERE id=").Append(newUser.Id).ToString() This doesn't properly put a , between any update parts after the first, for example: UPDATE users SET first_name='Firstname', last_name='lastname' WHERE id=... I could put in a mutable variable to keep track when the first part of the set clause is appended, but that seems wrong. I could just create an list of tuples, where each tuple is oldtext, newtext, columnname, so that I could then loop through the list and build up the query, but it seems that I should be passing in a StringBuilder to a recursive function, returning back a boolean which is then passed as a parameter to the recursive function. Does this seem to be the best approach, or is there a better one?

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