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  • Boolean Code Clarity - which style to use? [closed]

    - by Anonymous
    I was wondering what style others' use when writing conditional statements that include boolean types. Currently I'm caught between using two styles. bool foo; if (foo == true) if (foo) if (foo == false) if (!foo) Obviously the first set is a bit more obvious. However, when combining conditions it could get a bit clunky. if (foo == true || blah == false || abc == true) if (foo || !blah || abc) Switching between one style for short conditionals and the other for long conditionals seems like inconsistent coding so it seems like I'd have to choose between one or the other. What do you prefer or consider better style and why?

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  • SQL vs MySQL: Rules about aggregate operations and GROUP BY

    - by Phazyck
    In this book I'm currently reading while following a course on databases, the following example of an illegal query using an aggregate operator is given: Find the name and age of the oldest sailor. Consider the following attempt to answer this query: SELECT S.name, S.age FROM Sailors.S The intent is for this query to return not only the maximum age but also the name of the sailors having that age. However, this query is illegal in SQL--if the SELECT clause uses an aggregate operation, then it must use only aggregate operations unless the query contains a GROUP BY clause! Some time later while doing an exercise using MySQL, I faced a similar problem, and made a mistake similar to the one mentioned. However, MySQL didn't complain and just spit out some tables which later turned out not be what I needed. Is the query above really illegal in SQL, but legal in MySQL, and if so, why is that? In what situation would one need to make such a query?

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  • boolean type for while loop in bash?

    - by user151841
    I have a cron script on a shared web host that occasionally gets killed. I'd like to make a loop in bash that tries again if it gets killed, because most of the time it will make it. I'm having trouble with the syntax for storing a boolean value :P #!/bin/bash VAR=0; while [ $VAR ]; do if nice -19 mysqldump -uuser -ppassword -h database.hostname.com --skip-opt --all --complete-insert --add-drop-table database_name > ~/file/system/path/filename.sql; then VAR=1; fi done So the script recovers from a killed process okay, but once it's run properly, the new VAR value doesn't kill the while loop. What am I doing wrong?

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  • use boolean with visible, as3

    - by VideoDnd
    Is there a better way to do use a use a boolean with visible? This animation blinks 30 times and stops. It works without error, but takes a moment to load. I would like to learn other ways of using visibility with conditionals. var timz:Timer = new Timer(100,30); timz.addEventListener(TimerEvent.TIMER, doIt); var condition:Number = 5; function doIt(event:TimerEvent):void{ trace("fire!"); if(condition=5){ box.visible = !box.visible; } } timz.start();

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  • Approximate Number of CPU Cycles for Various Operations

    - by colordot
    I am trying to find a reference for approximately how many CPU cycles various operations require. I don't need exact numbers (as this is going to vary between CPUs) but I'd like something relatively credible that gives ballpark figures that I could cite in discussion with friends. As an example, we all know that floating point division takes more CPU cycles than say doing a bitshift. I'd guess that the difference is that the division is around 100 cycles, where as a shift is 1 but I'm looking for something to cite to back that up. Can anyone recommend such a resource?

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  • Checking if a boolean column is true in MySQL/Rails

    - by Pygmalion
    Rails and MySQL: I have a table with several boolean columns representing tags. I want to find all the rows for which a specific one of these columns is 'true' (or I guess in the case of MySQL, '1'). I have the following code in my view. @tag = params[:tag] @supplies = Supply.find(:all, :conditions=>["? IS NOT NULL and ? !=''", @tag, @tag], :order=>'name') The @tag is being passed in from the url. Why is it then that I am instead getting all of my @supplies (i.e. every row) rather than just those that are true for the column for @tag. Thanks!

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  • NHibernate Many-to-many with a boolean flag on the association table

    - by Nigel
    Hi I am doing some work on an application that uses an existing schema that cannot be altered. Whilst writing my NHibernate mappings I encountered a strange many-to-many relationship. The relationship is defined in the standard way as in this question with the addition of a boolean flag on the association table that signifies if the relationship is legal. This seems somewhat redundant but as I say, cannot be changed. Is it possible to define this relationship in Nhibernate without resorting to using a third class to represent the association? Perhaps by applying a filter? Many thanks.

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  • How can I do these operations in C?

    - by Juan Antonio
    Hello, I'm converting some assembly code to C to be able to use it with the current compiler environment I have to work with. I've reached 2 operations I don't know how to translate to C. Anyone know how to do it? In both, offset is an unsigned 32-bit integer and shift is a signed integer value. C_FLAG is a bool. OP1: __asm { __asm mov ecx, shift __asm ror offset, cl } OP2: __asm { __asm bt dword ptr C_FLAG, 0 __asm rcr offset, 1 } Thank you very much for your expertise. P.S.: I'm not the original developer, nor I have seen many x86 assembly code...

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  • Java: stopping long HTTP operations

    - by kilonet
    I'm using Apache Common library for HTTP operations: HttpClient client = getClient(); PutMethod put = new PutMethod(url); FileRequestEntity countingFileRequestEntity = new FileRequestEntity(file, "application/octet-stream"); put.setRequestEntity(countingFileRequestEntity); client.executeMethod(put); put.releaseConnection(); I wonder how can safely interrup long HTTP operation. Running it in new thread and stopping it seems to be wrong way. HttpMethodBase has abort() method, but I can't understand how to use it because client.executeMethod blocks execution until it complets

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  • How to check a bool setting in my iphone app

    - by dusk
    I have a setting in Root.plist with Key = 'latestNews' of type PSToggleSwitchSpecifier and DefaultValue as a boolean that is checked. If I understand that correctly, it should = YES when I pull it in to my code. I'm trying to check that value and set an int var to pass it to my php script. What is happening is that my boolean is either nil or NO and then my int var = 0. What am I doing wrong? int latestFlag; NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults]; BOOL latestNews = [prefs boolForKey:@"latestNews"]; if (latestNews) latestFlag = 1; else latestFlag = 0; NSString *urlstr = [[NSString alloc] initWithFormat:@"http://www.mysite.com/folder/iphone-test.php?latest=%d", latestFlag]; NSURL *url = [[NSURL alloc] initWithString:urlstr]; //these are auto-released NSString *ans = [NSString stringWithContentsOfURL:url]; NSArray *listItems = [ans componentsSeparatedByString:@","]; self.listData = listItems; [urlstr release]; [url release];

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  • How to Optimize Combined Graphical Operations?

    - by Sunny
    Hi, Here is a Scenario, A series of operations that I will call for painting, QPainter p(this); 1). p.fillRect(0,0,320,240, RED_COLOR) 2) p.drawLine(0,0,100,100, BLUE_COLOR) 3) p.fillRect(0,0,320,240, YELLOW_COLOR) Now I want that painter should not draw first FillRect Function. It should not draw line. It should only perform last operation. Is there any way to achive this optimization in Qt. Is this type of drawing/painting optimizations are supported by any library?

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  • How to use Boolean variable in c:if

    - by Patriks
    I am using this code in jsf <c:if test="#{sV.done.booleanValue()}"> <option value="#{sV.id}" selected="selected">#{sV.text}</option> </c:if> <c:if test="#{not sV.done.booleanValue()}"> <option value="#{sV.id}">#{sV.text}</option> </c:if> sv is my class containing data (pojo), done is an Boolean variable, I want to display option tag with selected attribute if sV.done is true. But I couldn't make it. Don't know where I am wrong. Otherwise there can be something worong with c? because c:forEach was not working before some time in my case in same page. it can be the reason? Where I am wrong?

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  • Three boolean values saved in one tinyint

    - by Casper
    Hello, probably a simple question but I seem to be suffering from programmer's block. :) I have three boolean values: A, B, and C. I would like to save the state combination as an unsigned tinyint (max 255) into a database and be able to derive the states from the saved integer. Even though there are only a limited number of combinations, I would like to avoid hard-coding each state combination to a specific value (something like if A=true and B=true has the value 1). I tried to assign values to the variables so (A=1, B=2, C=3) and then adding, but I can't differentiate between A and B being true from i.e. only C being true. I am stumped but pretty sure that it is possible. Thanks

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  • Performing multiple operations if condition is satisfied in ternary operator in linq

    - by user1575914
    I am a beginner in LINQ.I want to perform some conditional operation lik follows, (from emp in Employees let DOB=emp.BirthDate.GetValueOrDefault() let year=DOB.Year let month=DOB.Month let EmpAgeInYearsToday=DateTime.Now.Year-year let EmpAgeInMonthToday=DateTime.Now.Month-month let temp_year=(EmpAgeInYearsToday-1) let ExactNoOfMonths_temp=EmpAgeInMonthToday<0?temp_year:EmpAgeInMonthToday let ExactNoOfMonths=EmpAgeInMonthToday<0?EmpAgeInMonthToday+12&temp_year:EmpAgeInMonthToday select new{emp.EmployeeID,DOB, EmployeeAgeToday=EmpAgeInYearsToday+" Years "+ExactNoOfMonths+" Months ").Dump(); Here, let ExactNoOfMonths=EmpAgeInMonthToday<0?EmpAgeInMonthToday+12&temp_year:EmpAgeInMonthToday This part is not working. How to achieve this? How to perform multiple operations when the condition is satisfied?

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  • WCF: operations with out parameters are not supported

    - by Budda
    I've created a simple WCF service inside of WebApplication project. [ServiceContract(Namespace = "http://my.domain.com/service")] [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] public class MyService { [OperationContract] public string PublishProfile(out string enrollmentId, string registrationCode) { enrollmentId = null; return "Not supported"; } built - everything is compiled successfully After that I've tried to open service in browser, I've got the following error: Operation 'PublishProfile' in contract 'MyService' specifies an 'out' or 'ref' parameter. Operations with 'out' or 'ref' parameters are not supported Can't I use 'out' parameters? What is wrong here? Thanks

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  • How to model file system operations with REST?

    - by massive
    There are obvious counterparts for some of file systems' basic operations (eg. ls and rm), but how would you implement not straightforwardly RESTful actions such as cp or mv? As answers to the question REST services - exposing non-data “actions” suggest, the preferred way of implementing cp would include GETting the resource, DELETing it and PUTting it back again with a new name. But what if I would need to do it efficiently? For instance, if the resource's size would be huge? How would I eliminate the superfluous transmission of resource's payload to client and back to the originating server? Here is an illustration. I have a resource: /videos/my_videos/2-gigabyte-video.avi and I want copy it into a new resource: /videos/johns_videos/copied-2-gigabyte-video.avi How would I implement the copy, move or other file system actions the RESTful way? Or is there even a proper way? Am I doing it all wrong?

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  • Simple Java math operations

    - by user1730056
    I'm making a BMI calculator that doesn't seem to be working. The math operations work if i just do something like w/h, but once i had the brackets, it returns an error. If i change the variables w and h and use a constant number, the operation works. Another problem is that although i'm making result a double, it seems to be rounding to the nearest int. Could someone tell me what I'm doing wrong here? public class ass10 { public static void main(String[] args) { bmi(223,100); } public static bmi(int w, int h){ double result; result = (w/(h*h))*703 System.out.println(result) } }

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  • Using preg_match as boolean AND array

    - by silow
    I have this code where preg_match is used to break up a string into $pmarr array. Index 1 of that array is then being used to set a value $val = $pmarr[1]. $pmarr = array(); if (preg_match($expression, $orig, $pmarr)) { $val = $pmarr[1]; } What I'm wondering about is why the preg_match itself is being used as a boolean. If the expression doesn't match, does the array stay empty and therefore equate to false? Is the above code the same as saying preg_match($expression, $orig, $pmarr); if(isset($pmarr[1]) AND !empty($pmarr[1])){ $val = $pmarr[1]; }

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  • successives operations with C++

    - by Tayeb Ghagha
    How can I perform this code: if a number n is divisible by 3, add 4 to n; if n is not divisible by 3 but by 4, divise n by 2; if n is not divisible by 3, not by 4, make n=n-1. The problem with me is that I don't know how to make this successively. For example: with the number 6, I have to have: 6, 10, 9, 13, 12, 16, 8, 4, 2, 1 et 0 6+4=10; 10-1=9; 9+4=13; 13-1=12; 12+4=16; 16/2=8.....0 This makes 10 operations. So my program has to return: 6---10 Thank you for help

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  • Speed up bitstring/bit operations in Python?

    - by Xavier Ho
    I wrote a prime number generator using Sieve of Eratosthenes and Python 3.1. The code runs correctly and gracefully at 0.32 seconds on ideone.com to generate prime numbers up to 1,000,000. # from bitstring import BitString def prime_numbers(limit=1000000): '''Prime number generator. Yields the series 2, 3, 5, 7, 11, 13, 17, 19, 23, 29 ... using Sieve of Eratosthenes. ''' yield 2 sub_limit = int(limit**0.5) flags = [False, False] + [True] * (limit - 2) # flags = BitString(limit) # Step through all the odd numbers for i in range(3, limit, 2): if flags[i] is False: # if flags[i] is True: continue yield i # Exclude further multiples of the current prime number if i <= sub_limit: for j in range(i*3, limit, i<<1): flags[j] = False # flags[j] = True The problem is, I run out of memory when I try to generate numbers up to 1,000,000,000. flags = [False, False] + [True] * (limit - 2) MemoryError As you can imagine, allocating 1 billion boolean values (1 byte 4 or 8 bytes (see comment) each in Python) is really not feasible, so I looked into bitstring. I figured, using 1 bit for each flag would be much more memory-efficient. However, the program's performance dropped drastically - 24 seconds runtime, for prime number up to 1,000,000. This is probably due to the internal implementation of bitstring. You can comment/uncomment the three lines to see what I changed to use BitString, as the code snippet above. My question is, is there a way to speed up my program, with or without bitstring?

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  • Why can't I set boolean columns with update?

    - by Benjamin Oakes
    I'm making a user administration page. For the system I'm creating, users need to be approved. Sometimes, there will be many users to approve, so I'd like to make that easy. I'm storing this as a boolean column called approved. I remembered the Edit Multiple Individually Railscast and thought it would be a great fit. However, I'm running into problems which I traced back to ActiveRecord::Base#update. update works fine in this example: >> User.all.map(&:username) => ["ben", "fred"] >> h = {"1"=>{'username'=>'benjamin'}, "2"=>{"username"=>'frederick'}} => {"1"=>{"username"=>"benjamin"}, "2"=>{"username"=>"frederick"}} >> User.update(h.keys, h.values) => ... >> User.all.map(&:username) => ["benjamin", "frederick"] But not this one: >> User.all.map(&:approved) => [true, nil] >> h = {"1"=>{'approved'=>'1'}, "2"=>{'approved'=>'1'}} >> User.update(h.keys, h.values) => ... >> User.all.map(&:approved) => [true, nil] Chaging from '1' to true didn't make a difference when I tested. What am I doing wrong?

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  • Writing catch block with cleanup operations in Java ...

    - by kedarmhaswade
    I was not able to find any advise on catch blocks in Java that involve some cleanup operations which themselves could throw exceptions. The classic example is that of stream.close() which we usually call in the finally clause and if that throws an exception, we either ignore it by calling it in a try-catch block or declare it to be rethrown. But in general, how do I handle cases like: public void doIt() throws ApiException { //ApiException is my "higher level" exception try { doLower(); } catch(Exception le) { doCleanup(); //this throws exception too which I can't communicate to caller throw new ApiException(le); } } I could do: catch(Exception le) { try { doCleanup(); } catch(Exception e) { //ignore? //log? } throw new ApiException(le); //I must throw le } But that means I will have to do some log analysis to understand why cleanup failed. If I did: catch(Exception le) { try { doCleanup(); } catch(Exception e) { throw new ApiException(e); } It results in losing the le that got me here in the catch block in the fist place. What are some of the idioms people use here? Declare the lower level exceptions in throws clause? Ignore the exceptions during cleanup operation?

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  • C++ : Avoid lot of boolean variable for multiple verification conditions in trading app

    - by Naveen
    Hi i am a junior dev in trading app... we have a order refresh verification unit. It has to verify order confirmation from exchange. We send a bunch of different request in bulk ( NEW, MODIFY, CANCEL ) to exchange... Verification has to happen for max N times with each T intervals for all orders. if verification successful for all the order before N retry then fine.. otherwise we need to indicate as verification unsuccessfull. i hv done a basic coding done in very urgent like below for( N times ) { for_each ( sent_request_order ) // SENT { 1) get all the refreshed order from DB or shared mem i.e REFRESHED 2) find current sent order in REFRESHED if( not_found ) not refreshed from exchange, continue to next order if( found ) case NEW : //check for new status, mark verification done case MODIFY : //check for modified status.. //if not mark pending, go to next order, //revisit the same after T time case CANCEL : //check for cancelled status.. //if not mark pending, go to next order, //revisit the same after T time } if( all_verified ) exit from verification. wait ( T sec ) } order_verification_pending, order_verification_done, order_visited, order_not_visited, all_verified, all_not_verified ... lot of boolean flags used for indication.. is there any better approach for doing this.... splitting responsibilities across the classes......???? i know this is not a general question.... but still flags are making me tidious to handle...

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  • Long running operations (threads) in a web (asp.net) environment

    - by rrejc
    I have an asp.net (mvc) web site. As the part of the functions I will have to support some long running operations, for example: Initiated from user: User can upload (xml) file to the server. On the server I need to extract file, do some manipulation (insert into the db) etc... This can take from one minute to ten minutes (or even more - depends on file size). Of course I don't want to block the request when the import is running , but I want to redirect user to some progress page where he will have a chance to watch the status, errors or even cancel the import. This operation will not be frequently used, but it may happen that two users at the same time will try to import the data. It would be nice to run the imports in parallel. At the beginning I was thinking to create a new thread in the iis (controller action) and run the import in a new thread. But I am not sure if this is a good idea (to create working threads on a web server). Should I use windows services or any other approach? Initiated from system: - I will have to periodically update lucene index with the new data. - I will have to send mass emails (in the future). Should I implement this as a job in the site and run the job via Quartz.net or should I also create a windows service or something? What are the best practices when it comes to running site "jobs"? Thanks!

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  • Using SQL dB column as a lock for concurrent operations in Entity Framework

    - by Sid
    We have a long running user operation that is handled by a pool of worker processes. Data input and output is from Azure SQL. The master Azure SQL table structure columns are approximated to [UserId, col1, col2, ... , col N, beingProcessed, lastTimeProcessed ] beingProcessed is boolean and lastTimeProcessed is DateTime. The logic in every worker role is: public void WorkerRoleMain() { while(true) { try { dbContext db = new dbContext(); // Read foreach (UserProfile user in db.UserProfile .Where(u => DateTime.UtcNow.Subtract(u.lastTimeProcessed) > TimeSpan.FromHours(24) & u.beingProcessed == false)) { user.beingProcessed = true; // Modify db.SaveChanges(); // Write // Do some long drawn processing here ... ... ... user.lastTimeProcessed = DateTime.UtcNow; user.beingProcessed = false; db.SaveChanges(); } } catch(Exception ex) { LogException(ex); Sleep(TimeSpan.FromMinutes(5)); } } // while () } With multiple workers processing as above (each with their own Entity Framework layer), in essence beingProcessed is being used a lock for MutEx purposes Question: How can I deal with concurrency issues on the beingProcessed "lock" itself based on the above load? I think read-modify-write operation on the beingProcessed needs to be atomic but I'm open to other strategies. Open to other code refinements too.

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