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  • What's the use of writing tests matching configuration-like code line by line?

    - by Pascal Van Hecke
    Hi, I have been wondering about the usefulness of writing tests that match code one-by-one. Just an example: in Rails, you can define 7 restful routes in one line in routes.rb using: resources :products BDD/TDD proscribes you test first and then write code. In order to test the full effect of this line, devs come up with macros e.g. for shoulda: http://kconrails.com/2010/01/27/route-testing-with-shoulda-in-ruby-on-rails/ class RoutingTest < ActionController::TestCase # simple should_map_resources :products end I'm not trying to pick on the guy that wrote the macros, this is just an example of a pattern that I see all over Rails. I'm just wondering what the use of it is... in the end you're just duplicating code and the only thing you test is that Rails works. You could as well write a tool that transforms your test macros into actual code... When I ask around, people answer me that: "the tests should document your code, so yes it makes sense to write them, even if it's just one line corresponding to one line" What are your thoughts?

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  • Enumeration trouble: redeclared as different kind of symbol

    - by Matt
    Hello all. I am writing a program that is supposed to help me learn about enumeration data types in C++. The current trouble is that the compiler doesn't like my enum usage when trying to use the new data type as I would other data types. I am getting the error "redeclared as different kind of symbol" when compiling my trangleShape function. Take a look at the relevant code. Any insight is appreciated! Thanks! (All functions are their own .cpp files.) header file #ifndef HEADER_H_INCLUDED #define HEADER_H_INCLUDED #include <iostream> #include <iomanip> using namespace std; enum triangleType {noTriangle, scalene, isoceles, equilateral}; //prototypes void extern input(float&, float&, float&); triangleType extern triangleShape(float, float, float); /*void extern output (float, float, float);*/ void extern myLabel(const char *, const char *); #endif // HEADER_H_INCLUDED main function //8.1 main // this progam... #include "header.h" int main() { float sideLength1, sideLength2, sideLength3; char response; do //main loop { input (sideLength1, sideLength2, sideLength3); triangleShape (sideLength1, sideLength2, sideLength3); //output (sideLength1, sideLength2, sideLength3); cout << "\nAny more triangles to analyze? (y,n) "; cin >> response; } while (response == 'Y' || response == 'y'); myLabel ("8.1", "2/11/2011"); return 0; } triangleShape shape # include "header.h" triangleType triangleShape(sideLenght1, sideLength2, sideLength3) { triangleType triangle; return triangle; }

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  • MySQL query puzzle - finding what WOULD have been the most recent date

    - by Hank
    I've looked all over and haven't yet found an intelligent way to handle this, though I feel sure one is possible: One table of historical data has quarterly information: CREATE TABLE Quarterly ( unique_ID INT UNSIGNED NOT NULL, date_posted DATE NOT NULL, datasource TINYINT UNSIGNED NOT NULL, data FLOAT NOT NULL, PRIMARY KEY (unique_ID)); Another table of historical data (which is very large) contains daily information: CREATE TABLE Daily ( unique_ID INT UNSIGNED NOT NULL, date_posted DATE NOT NULL, datasource TINYINT UNSIGNED NOT NULL, data FLOAT NOT NULL, qtr_ID INT UNSIGNED, PRIMARY KEY (unique_ID)); The qtr_ID field is not part of the feed of daily data that populated the database - instead, I need to retroactively populate the qtr_ID field in the Daily table with the Quarterly.unique_ID row ID, using what would have been the most recent quarterly data on that Daily.date_posted for that data source. For example, if the quarterly data is 101 2009-03-31 1 4.5 102 2009-06-30 1 4.4 103 2009-03-31 2 7.6 104 2009-06-30 2 7.7 105 2009-09-30 1 4.7 and the daily data is 1001 2009-07-14 1 3.5 ?? 1002 2009-07-15 1 3.4 && 1003 2009-07-14 2 2.3 ^^ then we would want the ?? qtr_ID field to be assigned '102' as the most recent quarter for that data source on that date, and && would also be '102', and ^^ would be '104'. The challenges include that both tables (particularly the daily table) are actually very large, they can't be normalized to get rid of the repetitive dates or otherwise optimized, and for certain daily entries there is no preceding quarterly entry. I have tried a variety of joins, using datediff (where the challenge is finding the minimum value of datediff greater than zero), and other attempts but nothing is working for me - usually my syntax is breaking somewhere. Any ideas welcome - I'll execute any basic ideas or concepts and report back.

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  • Splitting a C++ class into files now won't compile.

    - by vgm64
    Hi. I am teaching myself to write classes in C++ but can't seem to get the compilation to go through. If you can help me figure out not just how, but why, it would be greatly appreciated. Thank you in advance! Here are my three files: make_pmt.C #include <iostream> #include "pmt.h" using namespace std; int main() { CPMT *pmt = new CPMT; pmt->SetVoltage(900); pmt->SetGain(2e6); double voltage = pmt->GetVoltage(); double gain= pmt->GetGain(); cout << "The voltage is " << voltage << " and the gain is " << gain << "." <<endl; return 0; } pmt.C #include "pmt.h" using namespace std; class CPMT { double gain, voltage; public: double GetGain() {return gain;} double GetVoltage() {return voltage;} void SetGain(double g) {gain=g;} void SetVoltage(double v) {voltage=v;} }; pmt.h #ifndef PMT_H #define PMT_H 1 using namespace std; class CPMT { double gain, voltage; public: double GetGain(); double GetVoltage(); void SetGain(double g); void SetVoltage(double v); }; #endif And for reference, I get a linker error (right?): Undefined symbols: "CPMT::GetVoltage()", referenced from: _main in ccoYuMbH.o "CPMT::GetGain()", referenced from: _main in ccoYuMbH.o "CPMT::SetVoltage(double)", referenced from: _main in ccoYuMbH.o "CPMT::SetGain(double)", referenced from: _main in ccoYuMbH.o ld: symbol(s) not found collect2: ld returned 1 exit status

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  • What to pass parameters to start an workflow through WCF

    - by Rubens Farias
    It's possible to define some start values to an workflow using WorkflowInstance.CreateWorkflow, like this: using(WorkflowRuntime runtime = new WorkflowRuntime()) { Dictionary<string, object> parameters = new Dictionary<string, object>(); parameters.Add("First", "something"); parameters.Add("Second", 42); WorkflowInstance instance = runtime.CreateWorkflow(typeof(MyStateMachineWorkflow), parameters); instance.Start(); waitHandle.WaitOne(); } This way, a MyStateMachineWorkflow instance is created and First and Second public properties gets that dictionary values. But I'm using WCF; so far, I managed to create a Start method which accepts that two arguments and I set that required fields by using bind on my ReceiveActivity: using (WorkflowServiceHost host = new WorkflowServiceHost(typeof(MyStateMachineWorkflow))) { host.Open(); ChannelFactory<IMyStateMachineWorkflow> factory = new ChannelFactory<IMyStateMachineWorkflow>("MyStateMachineWorkflow"); IMyStateMachineWorkflow proxy = factory.CreateChannel(); // set this values through binding on my ReceiveActivity proxy.Start("something", 42); } While this works, that create an anomaly: that method should be called only and exactly once. How can I start an workflow instance through WCF passing those arguments? On my tests, I just actually interact with my workflow through wire after I call that proxy method. Is there other way?

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  • HQL query problem

    - by yigit
    Hi all, I'm using this hql query for my filters. Query perfectly working except width (string) part. Here is the query, public IList<ColorGroup> GetDistinctColorGroups(int typeID, int finishID, string width) { string queryStr = "Select distinct c from ColorGroup c inner join c.Products p " + "where p.ShowOnline = 1 "; if (typeID > 0) queryStr += " and p.ProductType.ID = " + typeID; if (finishID > 0) queryStr += " and p.FinishGroup.ID = " + finishID; if (width != "") queryStr += " and p.Size.Width = " + width; IList<ColorGroup> colors = NHibernateSession.CreateQuery(queryStr).List<ColorGroup>(); return colors; } ProductType and Size have same mappings and relations. This is the error; NHibernate.QueryException: illegal syntax near collection: Size [Select distinct c from .Domain.ColorGroup c inner join c.Products p where p.ShowOnline = 1 and p.ProductType.ID = 1 and p.FinishGroup.ID = 5 and p.Size.Width = 4] Any ideas ?

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  • Is it possible in Perl to require a subroutine call is made?

    - by MitchelWB
    I don't know enough about Perl to even know what I'm asking for exactly, but I'm writing a series of subroutines to be available for many individual scripts that all process different incoming flat files. The process is far from perfect, but it's what I've got to deal with and I'm trying to build myself a small library of subs that make it easier for me to manage it all. Each script handles a different incoming flat file with it's own formatting, sorting, grouping and outputting requirements. One common aspect is that we have small text files that house counters that are used to name the output files so that we have no duplicate file names. Because the processing of the data is different for each file, I need to open the file to get my counter value, because this is a common operation, I'd like to put it in a sub to retrieve the counter. But then need to write specific code to process the data. And would like a second sub that allows me to update the counter with the counter once I've processed the data. Is there a way to make the second sub call a requirement if the first one is called? Ideally if it could even be an error that would prevent the script from running at all much like a syntax error. EDIT: Here is a little [ugly and simplified] psuedo-code to give a better feel for what the current process is: require "importLibrary.plx"; #open data source file open DataIn, $filename; #call getCounterInfo from importLibrary.plx to get the counter value from counter file $counter = &getCounterInfo($counterFileName); while (<DataIn>) { #Process data based on unique formatting and requirements #output to task files based on requirements and name files using the $counter #increment $counter } #update counter file with new value of $counter &updateCounterInfo($counter);

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  • An error saying unidentifed function "push", "pop", and"display" occurs, what should i add to fix i

    - by Alesha Aris
    #include<stdio.h> #include<iostream.h> #include<conio.h> #include<stdlib.h>(TOP) #include<fstream.h> #define MAX 5 int top = -1; int stack_arr[MAX]; main() { int choice; while(1) { printf("1.Push\n"); printf("2.Pop\n"); printf("3.Display\n"); printf("4.Quit\n"); printf("Enter your choice : "); scanf("%d",&choice); switch(choice) { case 1 : push(); break; case 2: pop(); break; case 3: display(); break; case 4: exit(1); default: printf("Wrong choice\n"); }/*End of switch*/ }/*End of while*/ }/*End of main()*/ push() { int pushed_item; if(top == (MAX-1)) printf("Stack Overflow\n"); else { printf("Enter the item to be pushed in stack : "); scanf("%d",&pushed_item); top=top+1; stack_arr[top] = pushed_item; } }/*End of push()*/ pop() { if(top == -1) printf("Stack Underflow\n"); else { printf("Popped element is : %d\n",stack_arr[top]); top=top-1; } }/*End of pop()*/ display() { int i; if(top == -1) printf("Stack is empty\n"); else { printf("Stack elements :\n"); for(i = top; i >=0; i--) printf("%d\n", stack_arr[i] ); } }/*End of display()*/

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  • Multiple usage of MenuItems declared once (WPF)

    - by Alex Kofman
    Is it possible in WPF to define some menu structure and than use it in multiple contexts? For example I'd like to use a set of menu items from resources in ContextMenu, Window's menu and ToolBar (ToolBar with icons only, without headers). So items order, commands, icons, separators must be defined just once. I look for something like this: Declaration in resources: <MenuItem Command="MyCommands.CloneObject" CommandParameter="{Binding SelectedObject}" Header="Clone"> <MenuItem.Icon> <Image Source="Images\Clone.png" Height="16" Width="16"></Image> </MenuItem.Icon> </MenuItem> <MenuItem Command="MyCommands.RemoveCommand" CommandParameter="{Binding SelectedObject}" Header="Remove"> <MenuItem.Icon> <Image Source="Images\Remove.png" Height="16" Width="16"></Image> </MenuItem.Icon> </MenuItem> <Separator/> <MenuItem Command="MCommands.CreateChild" CommandParameter="{Binding SelectedObject}" Header="Create child"> <MenuItem.Icon> <Image Source="Images\Child.png" Height="16" Width="16"></Image> </MenuItem.Icon> </MenuItem> Usage: <ToolBar MenuItems(?)="{Reference to set of items}" ShowText(?)="false" /> and <ContextMenu MenuItems(?)="{Reference to set of items}" />

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  • How do I implement a collection in Scala 2.8?

    - by Simon Reinhardt
    In trying to write an API I'm struggling with Scala's collections in 2.8(.0-beta1). Basically what I need is to write something that: adds functionality to immutable sets of a certain type where all methods like filter and map return a collection of the same type without having to override everything (which is why I went for 2.8 in the first place) where all collections you gain through those methods are constructed with the same parameters the original collection had (similar to how SortedSet hands through an ordering via implicits) which is still a trait in itself, independent of any set implementations. Additionally I want to define a default implementation, for example based on a HashSet. The companion object of the trait might use this default implementation. I'm not sure yet if I need the full power of builder factories to map my collection type to other collection types. I read the paper on the redesign of the collections API but it seems like things have changed a bit since then and I'm missing some details in there. I've also digged through the collections source code but I'm not sure it's very consistent yet. Ideally what I'd like to see is either a hands-on tutorial that tells me step-by-step just the bits that I need or an extensive description of all the details so I can judge myself which bits I need. I liked the chapter on object equality in "Programming in Scala". :-) But I appreciate any pointers to documentation or examples that help me understand the new collections design better.

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  • C++ Initialize array in constructor EXC_BAD_ACCESS

    - by user890395
    I'm creating a simple constructor and initializing an array: // Construtor Cinema::Cinema(){ // Initalize reservations for(int i = 0; i < 18; i++){ for(int j = 0; j < 12; j++){ setReservation(i, j, 0); } } // Set default name setMovieName("N/A"); // Set default price setPrice(8); } The setReservation function: void Cinema::setReservation(int row, int column, int reservation){ this->reservations[row][column] = reservation; } The setMovieName function: void Cinema::setMovieName(std::string movieName){ this->movieName = movieName; } For some odd reason when I run the program, the setMovieName function gives the following error: "Program Received Signal: EXC_BAD_ACCESS" If I take out the for-loop that initializes the array of reservations, the problem goes away and the movie name is set without any problems. Any idea what I'm doing wrong? This is the Cinema.h file: #ifndef Cinema_h #define Cinema_h class Cinema{ private: int reservations[17][11]; std::string movieName; float price; public: // Construtor Cinema(); // getters/setters int getReservation(int row, int column); int getNumReservations(); std::string getMovieName(); float getPrice(); void setReservation(int row, int column, int reservation); void setMovieName(std::string movieName); void setPrice(float price); }; #endif

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  • Change a finder method w/ parameters to an association

    - by Sai Emrys
    How do I turn this into a has_one association? (Possibly has_one + a named scope for size.) class User < ActiveRecord::Base has_many :assets, :foreign_key => 'creator_id' def avatar_asset size = :thumb # The LIKE is because it might be a .jpg, .png, or .gif. # More efficient methods that can handle that are OK. ;) self.assets.find :first, :conditions => ["thumbnail = '#{size}' and filename LIKE ?", self.login + "_#{size}.%"] end end EDIT: Cuing from AnalogHole on Freenode #rubyonrails, we can do this: has_many :assets, :foreign_key => 'creator_id' do def avatar size = :thumb find :first, :conditions => ["thumbnail = ? and filename LIKE ?", size.to_s, proxy_owner.login + "_#{size}.%"] end end ... which is fairly cool, and makes syntax a bit better at least. However, this still doesn't behave as well as I would like. Particularly, it doesn't allow for further nice find chaining (such that it doesn't execute this find until it's gotten all its conditions). More importantly, it doesn't allow for use in an :include. Ideally I want to do something like this: PostsController def show post = Post.get_cache(params[:id]) { Post.find(params[:id], :include => {:comments => {:users => {:avatar_asset => :thumb}} } ... end ... so that I can cache the assets together with the post. Or cache them at all, really - e.g. get_cache(user_id){User.find(user_id, :include => :avatar_assets)} would be a good first pass. This doesn't actually work (self == User), but is correct in spirit: has_many :avatar_assets, :foreign_key => 'creator_id', :class_name => 'Asset', :conditions => ["filename LIKE ?", self.login + "_%"] (Also posted on Refactor My Code.)

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  • Dynamic evaluation of a table column within an insert before trigger

    - by Tim Garver
    HI All, I have 3 tables, main, types and linked. main has an id column and 32 type columns. types has id, type linked has id, main_id, type_id I want to create an insert before trigger on the main table. It needs to compare its 32 type columns to the values in the types table if the main table column has an 'X' for its value and insert the main_id and types_id into the linked table. i have done a lot of searching, and it looks like a prepared statement would be the way to go, but i wanted to ask the experts. The issue, is i dont want to write 32 IF statements, and even if i did, i need to query the types table to get the ID for that type, seems like a huge waist of resources. Ideally i want to do this inside of my trigger: BEGIN DECLARE @types results_set -- (not sure if this is a valid type); -- (iam sure my loop syntax is all wrong here)... SET @types = (select * from types) for i=0;i<types.records;i++ { IF NEW.[i.type] = 'X' THEN insert into linked (main_id,type_id) values (new.ID, i.id); END IF; } END; Anyway, This is what i was hoping to do, maybe there is a way to dynamically set the field name inside of a results loop, but i cant find a good example of this. Thanks in advance Tim

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  • Stored Procedure Parameters Not Available After Declared

    - by SidC
    Hi All, Pasted below is a stored procedure written in SQL Server 2005. My intent is to call this sproc from my ASP.NEt web application through the use of a wizard control. I am new to SQL Server and especially to stored procedures. I'm unsure why my parameters are not available to the web application and not visible in SSMS treeview as a parameter under my sproc name. Can you help me correct the sproc below so that the parameters are correctly instantiated and available for use in my web application? Thanks, Sid Stored Procedure syntax: USE [Diel_inventory] GO /****** Object: StoredProcedure [dbo].[AddQuote] Script Date: 05/09/2010 00:31:10 ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO ALTER procedure [dbo].[AddQuote] as Declare @CustID int, @CompanyName nvarchar(50), @Address nvarchar(50), @City nvarchar(50), @State nvarchar(2), @ZipCode nvarchar(5), @Phone nvarchar(12), @FAX nvarchar(12), @Email nvarchar(50), @ContactName nvarchar(50), @QuoteID int, @QuoteDate datetime, @NeedbyDate datetime, @QuoteAmt decimal, @ID int, @QuoteDetailPartID int, @PartNumber float, @Quantity int begin Insert into dbo.Customers (CompanyName, Address, City, State, ZipCode, OfficePhone, OfficeFAX, Email, PrimaryContactName) Values (@CompanyName, @Address, @City, @State, @ZipCode, @Phone, @FAX, @Email, @ContactName) set @CustID = scope_identity() Insert into dbo.Quotes (fkCustomerID,NeedbyDate,QuoteAmt) Values(@CustID,@NeedbyDate,@QuoteAmt) set @QuoteID = scope_identity() Insert into dbo.QuoteDetail (ID) values(@ID) set @ID=scope_identity() Insert into dbo.QuoteDetailParts (QuoteDetailPartID, QuoteDetailID, PartNumber, Quantity) values (@ID, @QuoteDetailPartID, @PartNumber, @Quantity) END

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  • MSMQ - Message Queue Abstraction and Pattern

    - by Maxim Gershkovich
    Hi All, Let me define the problem first and why a messagequeue has been chosen. I have a datalayer that will be transactional and EXTREMELY insert heavy and rather then attempt to deal with these issues when they occur I am hoping to implement my application from the ground up with this in mind. I have decided to tackle this problem by using the Microsoft Message Queue and perform inserts as time permits asynchronously. However I quickly ran into a problem. Certain inserts that I perform may need to be recalled (ie: retrieved) immediately (imagine this is for POS system and what happens if you need to recall the last transaction - one that still hasn’t been inserted). The way I decided to tackle this problem is by abstracting the MessageQueue and combining it in my data access layer thereby creating the illusion of a single set of data being returned to the user of the datalayer (I have considered the other issues that occur in such a scenario (ie: essentially dirty reads and such) and have concluded for my purposes I can control these issues). However this is where things get a little nasty... I’ve worked out how to get the messages back and such (trivial enough problem) but where I am stuck is; how do I create a generic (or at least somewhat generic) way of querying my message queue? One where I can minimize the duplication between the SQL queries and MessageQueue queries. I have considered using LINQ (but have very limited understanding of the technology) and have also attempted an implementation with Predicates which so far is pretty smelly. Are there any patterns for such a problem that I can utilize? Am I going about this the wrong way? Does anyone have an of their own ideas about how I can tackle this problem? Does anyone even understand what I am talking about? :-) Any and ALL input would be highly appreciated and seriously considered… Thanks again.

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  • C# Multiple constraints

    - by John
    I have an application with lots of generics and IoC. I have an interface like this: public interface IRepository<TType, TKeyType> : IRepo Then I have a bunch of tests for my different implementations of IRepository. Many of the objects have dependencies on other objects so for the purpose of testing I want to just grab one that is valid. I can define a separate method for each of them: public static EmailType GetEmailType() { return ContainerManager.Container.Resolve<IEmailTypeRepository>().GetList().FirstOrDefault(); } But I want to make this generic so it can by used to get any object from the repository it works with. I defined this: public static R GetItem<T, R>() where T : IRepository<R, int> { return ContainerManager.Container.Resolve<T>().GetList().FirstOrDefault(); } This works fine for the implementations that use an integer for the key. But I also have repositories that use string. So, I do this now: public static R GetItem<T, R, W>() where T : IRepository<R, W> This works fine. But I'd like to restrict 'W' to either int or string. Is there a way to do that? The shortest question is, can I constrain a generic parameter to one of multiple types?

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  • Concept: Is mongo right for applying schemas?

    - by Jan
    I am currently in charge of checking wether it is valuable for one of our upcoming products to be developed on mongo. Without going too much into detail, I'll try to explain, what the app does. The app simply has "entities". These entities are technical stuff, like cell phones, TVs, Laptops, tablet pcs, and so forth. Of course, a cell phone has other attributes than a Tablet PCs and a Laptop has even other attributes, like RAM, CPU, display size and so on. Now I want to have something that we wanna call a scheme: We define that we need to have saved the display size, amount of ram size of flash devices, processor type, processor speed and so on for tablet pcs. For cell phone we might save display size, GSM, Edge, 3g, 4g, processor, ram, touch screen technology, bla bla bla. I think you got it :) What I want to realize is, that each "category" has a schema and when one of the system's users enters a new product (let's say the new iphone 4), the app constructs the form to be filled out with the appropriate attributes. So far it sounds nice and should not be a problem with mongo. But now the tough for which I could not find a clean solution.... An attribute modeled in mongo looks like: { _id: 1234456, name: "Attribute name", type: 0, "description" } But what to do, if i need this attribute in several languages, like: { en: {name: "Attribute name", type: 0, "description"}, de: {name: "Name des Attributs, type: 0, "Beschreibung"} } I also need to ensure that the german attribute gets updated as soon as the english gets updated, for instance when type changes from 0 to 1. Any ideas on that?

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  • Beginner SQL section: avoiding repeated expression

    - by polygenelubricants
    I'm entirely new at SQL, but let's say that on the StackExchange Data Explorer, I just want to list the top 15 users by reputation, and I wrote something like this: SELECT TOP 15 DisplayName, Id, Reputation, Reputation/1000 As RepInK FROM Users WHERE RepInK > 10 ORDER BY Reputation DESC Currently this gives an Error: Invalid column name 'RepInK', which makes sense, I think, because RepInK is not a column in Users. I can easily fix this by saying WHERE Reputation/1000 > 10, essentially repeating the formula. So the questions are: Can I actually use the RepInK "column" in the WHERE clause? Do I perhaps need to create a virtual table/view with this column, and then do a SELECT/WHERE query on it? Can I name an expression, e.g. Reputation/1000, so I only have to repeat the names in a few places instead of the formula? What do you call this? A substitution macro? A function? A stored procedure? Is there an SQL quicksheet, glossary of terms, language specification, anything I can use to quickly pick up the syntax and semantics of the language? I understand that there are different "flavors"?

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  • Modules vs. Classes and their influence on descendants of ActiveRecord::Base

    - by Chris
    Here's a Ruby OO head scratcher for ya, brought about by this Rails scenario: class Product < ActiveRecord::Base has_many(:prices) # define private helper methods end module PrintProduct attr_accessor(:isbn) # override methods in ActiveRecord::Base end class Book < Product include PrintProduct end Product is the base class of all products. Books are kept in the products table via STI. The PrintProduct module brings some common behavior and state to descendants of Product. Book is used inside fields_for blocks in views. This works for me, but I found some odd behavior: After form submission, inside my controller, if I call a method on a book that is defined in PrintProduct, and that method calls a helper method defined in Product, which in turn calls the prices method defined by has_many, I'll get an error complaining that Book#prices is not found. Why is that? Book is a direct descendant of Product! More interesting is the following.. As I developed this hierarchy PrintProduct started to become more of an abstract ActiveRecord::Base, so I thought it prudent to redefine everything as such: class Product < ActiveRecord::Base end class PrintProduct < Product end class Book < PrintProduct end All method definitions, etc. are the same. In this case, however, my web form won't load because the attributes defined by attr_accessor (which are "virtual attributes" referenced by the form but not persisted in the DB) aren't found. I'll get an error saying that there is no method Book#isbn. Why is that?? I can't see a reason why the attr_accessor attributes are not found inside my form's fields_for block when PrintProduct is a class, but they are found when PrintProduct is a Module. Any insight would be appreciated. I'm dying to know why these errors are occurring!

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  • C++ compiler unable to find function (namespace related)

    - by CS student
    I'm working in Visual Studio 2008 on a C++ programming assignment. We were supplied with files that define the following namespace hierarchy (the names are just for the sake of this post, I know "namespace XYZ-NAMESPACE" is redundant): (MAIN-NAMESPACE){ a bunch of functions/classes I need to implement... (EXCEPTIONS-NAMESPACE){ a bunch of exceptions } (POINTER-COLLECTIONS-NAMESPACE){ Set and LinkedList classes, plus iterators } } The MAIN-NAMESPACE contents are split between a bunch of files, and for some reason which I don't understand the operator<< for both Set and LinkedList is entirely outside of the MAIN-NAMESPACE (but within Set and LinkedList's header file). Here's the Set version: template<typename T> std::ostream& operator<<(std::ostream& os, const MAIN-NAMESPACE::POINTER-COLLECTIONS-NAMESPACE::Set<T>& set) Now here's the problem: I have the following data structure: Set A Set B Set C double num It's defined to be in a class within MAIN-NAMESPACE. When I create an instance of the class, and try to print one of the sets, it tells me that: error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'const MAIN-NAMESPACE::POINTER-COLLECTIONS-NAMESPACE::Set' (or there is no acceptable conversion) However, if I just write a main() function, and create Set A, fill it up, and use the operator- it works. Any idea what is the problem? (note: I tried any combination of using and include I could think of).

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  • Linking Apache to Tomcat with multiple domains.

    - by Royce Thigpen
    Okay, so I've been working for a while on this, and have been searching, but so far I have not found any answers that actually answer what I want to know. I'm a little bit at the end of my rope with this one, but I'm hoping I can figure this out sometime soon. So I have Apache 2 installed and serving up standard webpages, but I also have that linked to a Tomcat instance for one of my domains currently supported. However, I want to add another domain to the server via Apache that points to a separate code base from the one I already have. I have been coming at this from several different angles, and I have determined that I just don't know enough about setting up these servers to really do what I want to do. Little information on my server: Currently running a single Tomcat5.5 instance with Apache 2, using mod_jk to connect them together. I have a worker in workers.properties that points it's "host" field to "localhost" with the correct port my Tomcat instance, so that all works. In my Tomcat server.xml file, I have a host defined as "localhost" that points at my webapp that I am currently serving up, with that host set as the defaultHost as well. One thought I had was that I could add a new worker with a different host than "localhost" (i.e. host2) and then define a new host in my server.xml file called "host2" to match it, but after reading around some on the internet, It seems the "host" of the worker must point to a server, and not a hostname in the Tomcat instance, is this correct? Again, a simple rundown of what I want: Setup in apache/tomcat combo such that www.domain1.com points at "webapp1" and www.domain2.com points at "webapp2".

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  • How can variadic char template arguments from user defined literals be converted back into numeric types?

    - by Pubby
    This question is being asked because of this one. C++11 allows you to define literals like this for numeric literals: template<char...> OutputType operator "" _suffix(); Which means that 503_suffix would become <'5','0','3'> This is nice, although it isn't very useful in the form it's in. How can I transform this back into a numeric type? This would turn <'5','0','3'> into a constexpr 503. Additionally, it must also work on floating point literals. <'5','.','3> would turn into int 5 or float 5.3 A partial solution was found in the previous question, but it doesn't work on non-integers: template <typename t> constexpr t pow(t base, int exp) { return (exp > 0) ? base * pow(base, exp-1) : 1; }; template <char...> struct literal; template <> struct literal<> { static const unsigned int to_int = 0; }; template <char c, char ...cv> struct literal<c, cv...> { static const unsigned int to_int = (c - '0') * pow(10, sizeof...(cv)) + literal<cv...>::to_int; }; // use: literal<...>::to_int // literal<'1','.','5'>::to_int doesn't work // literal<'1','.','5'>::to_float not implemented

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  • Omit return type in C++0x

    - by Clinton
    I've recently found myself using the following macro with gcc 4.5 in C++0x mode: #define RETURN(x) -> decltype(x) { return x; } And writing functions like this: template <class T> auto f(T&& x) RETURN (( g(h(std::forward<T>(x))) )) I've been doing this to avoid the inconvenience having to effectively write the function body twice, and having keep changes in the body and the return type in sync (which in my opinion is a disaster waiting to happen). The problem is that this technique only works on one line functions. So when I have something like this (convoluted example): template <class T> auto f(T&& x) -> ... { auto y1 = f(x); auto y2 = h(y1, g1(x)); auto y3 = h(y1, g2(x)); if (y1) { ++y3; } return h2(y2, y3); } Then I have to put something horrible in the return type. Furthermore, whenever I update the function, I'll need to change the return type, and if I don't change it correctly, I'll get a compile error if I'm lucky, or a runtime bug in the worse case. Having to copy and paste changes to two locations and keep them in sync I feel is not good practice. And I can't think of a situation where I'd want an implicit cast on return instead of an explicit cast. Surely there is a way to ask the compiler to deduce this information. What is the point of the compiler keeping it a secret? I thought C++0x was designed so such duplication would not be required.

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  • my dialog box did not show up whene i compile it using sdk 7.1,

    - by zirek
    hello and welcom everyone .. i'd like to build a win32 application using sdk 7.1, i create the dialog box using visual c++ 2012 resource editor, i copy resource.rc and resource.h to my folder and i write this simple main.cpp file: #include <windowsx.h> #include <Windows.h> #include <tchar.h> #include "resource.h" #define my_PROCESS_MESSAGE(hWnd, message, fn) \ case(message): \ return( \ SetDlgMsgResult(hWnd, uMsg, \ HANDLE_##message((hWnd), (wParam), (lParam), (fn)) )) \ LRESULT CALLBACK DlgProc(HWND, UINT, WPARAM, LPARAM); BOOL Cls_OnInitDialog(HWND hwnd, HWND hwndFocus, LPARAM lParam); void Cls_OnCommand(HWND hwnd, int id, HWND hwndCtl, UINT codeNotify); int WINAPI _tWinMain( HINSTANCE hInstance, HINSTANCE, LPTSTR, int iCmdLine ) { DialogBoxParam( hInstance, MAKEINTRESOURCE(IDD_INJECTOR), NULL, (DLGPROC) DlgProc, NULL ); return FALSE; } LRESULT CALLBACK DlgProc( HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam ) { switch (uMsg) { my_PROCESS_MESSAGE(hwnd, WM_INITDIALOG, Cls_OnInitDialog); my_PROCESS_MESSAGE(hwnd, WM_COMMAND, Cls_OnCommand); default: break; } return DefWindowProc(hwnd, uMsg, wParam, lParam); } BOOL Cls_OnInitDialog(HWND hwnd, HWND hwndFocus, LPARAM lParam) { return TRUE; } void Cls_OnCommand(HWND hwnd, int id, HWND hwndCtl, UINT codeNotify) { switch(id) { case IDCANCEL: EndDialog(hwnd, id); break; default: break; } } then i use the following command line to compile my code, wich i found on this forum cl main.cpp /link /SUBSYSTEM:WINDOWS user32.lib my problem is that my dialog box did not show up, and when i use procexp, to see what happen, i found that that my application is created then closed in the same time, and what make me wondering is that its working fine on visual c++ 2012. my sdk 7.1, installed correctly, i testing it against a basic window without any resource file any ideas, ill be really thankful Best, Zirek

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  • @selector and return value

    - by user320926
    The idea it's very easy, i have an http download class, this class must support the http authentication but it's basically a background thread so i would like to avoid to prompt directly to the screen, i would like to use a delegate method to require from outside of the class, like a viewController. But i don't know if is possible or if i have to use a different syntax. This class use this delegate protocol: //Updater.h @protocol Updater <NSObject> -(NSDictionary *)authRequired; @optional -(void)statusUpdate:(NSString *)newStatus; -(void)downloadProgress:(int)percentage; @end @interface Updater : NSThread { ... } This is the call to the delegate method: //Updater.m // This check always fails :( if ([self.delegate respondsToSelector:@selector(authRequired:)]) { auth = [delegate authRequired]; } This is the implementation of the delegate method //rootViewController.m -(NSDictionary *)authRequired; { // TODO: some kind of popup or modal view NSMutableDictionary *ret=[[NSMutableDictionary alloc] init]; [ret setObject:@"utente" forKey:@"user"]; [ret setObject:@"password" forKey:@"pass"]; return ret; }

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