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• The idea of functionN in Scala / Functionaljava

  - by Luke Murphy

  From brain driven development It turns out, that every Function you’ll ever define in Scala, will become an instance of an Implementation which will feature a certain Function Trait. There is a whole bunch of that Function Traits, ranging from Function1 up to Function22. Since Functions are Objects in Scala and Scala is a statically typed language, it has to provide an appropriate type for every Function which comes with a different number of arguments. If you define a Function with two arguments, the compiler picks Function2 as the underlying type. Also, from Michael Froh's blog You need to make FunctionN classes for each number of parameters that you want? Yes, but you define the classes once and then you use them forever, or ideally they're already defined in a library (e.g. Functional Java defines classes F, F2, ..., F8, and the Scala standard library defines classes Function1, ..., Function22) So we have a list of function traits (Scala), and a list of interfaces (Functional-java) to enable us to have first class funtions. I am trying to understand exactly why this is the case. I know, in Java for example, when I write a method say, public int add(int a, int b){ return a + b; } That I cannot go ahead and write add(3,4,5); ( error would be something like : method add cannot be applied to give types ) We simply have to define an interface/trait for functions with different parameters, because of static typing?

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• SQL Server Date Comparison Functions

  - by HighAltitudeCoder

  A few months ago, I found myself working with a repetitive cursor that looped until the data had been manipulated enough times that it was finally correct.  The cursor was heavily dependent upon dates, every time requiring the earlier of two (or several) dates in one stored procedure, while requiring the later of two dates in another stored procedure. In short what I needed was a function that would allow me to perform the following evaluation: WHERE MAX(Date1, Date2) < @SomeDate The problem is, the MAX() function in SQL Server does not perform this functionality.  So, I set out to put these functions together.  They are titled: EarlierOf() and LaterOf(). /**********************************************************                               EarlierOf.sql   **********************************************************/ /**********************************************************   Return the later of two DATETIME variables.   Parameter 1: DATETIME1 Parameter 2: DATETIME2   Works for a variety of DATETIME or NULL values. Even though comparisons with NULL are actually indeterminate, we know conceptually that NULL is not earlier or later than any other date provided.   SYNTAX: SELECT dbo.EarlierOf('1/1/2000','12/1/2009') SELECT dbo.EarlierOf('2009-12-01 00:00:00.000','2009-12-01 00:00:00.521') SELECT dbo.EarlierOf('11/15/2000',NULL) SELECT dbo.EarlierOf(NULL,'1/15/2004') SELECT dbo.EarlierOf(NULL,NULL)   **********************************************************/ USE AdventureWorks GO   IF EXISTS       (SELECT *       FROM sysobjects       WHERE name = 'EarlierOf'       AND xtype = 'FN'       ) BEGIN             DROP FUNCTION EarlierOf END GO   CREATE FUNCTION EarlierOf (       @Date1                              DATETIME,       @Date2                              DATETIME )   RETURNS DATETIME   AS BEGIN       DECLARE @ReturnDate     DATETIME         IF (@Date1 IS NULL AND @Date2 IS NULL)       BEGIN             SET @ReturnDate = NULL             GOTO EndOfFunction       END         ELSE IF (@Date1 IS NULL AND @Date2 IS NOT NULL)       BEGIN             SET @ReturnDate = @Date2             GOTO EndOfFunction       END         ELSE IF (@Date1 IS NOT NULL AND @Date2 IS NULL)       BEGIN             SET @ReturnDate = @Date1             GOTO EndOfFunction       END         ELSE       BEGIN             SET @ReturnDate = @Date1             IF @Date2 < @Date1                   SET @ReturnDate = @Date2             GOTO EndOfFunction       END         EndOfFunction:       RETURN @ReturnDate   END -- End Function GO   ---- Set Permissions --GRANT SELECT ON EarlierOf TO UserRole1 --GRANT SELECT ON EarlierOf TO UserRole2 --GO                                                                                             The inverse of this function is only slightly different. /**********************************************************                               LaterOf.sql   **********************************************************/ /**********************************************************   Return the later of two DATETIME variables.   Parameter 1: DATETIME1 Parameter 2: DATETIME2   Works for a variety of DATETIME or NULL values. Even though comparisons with NULL are actually indeterminate, we know conceptually that NULL is not earlier or later than any other date provided.   SYNTAX: SELECT dbo.LaterOf('1/1/2000','12/1/2009') SELECT dbo.LaterOf('2009-12-01 00:00:00.000','2009-12-01 00:00:00.521') SELECT dbo.LaterOf('11/15/2000',NULL) SELECT dbo.LaterOf(NULL,'1/15/2004') SELECT dbo.LaterOf(NULL,NULL)   **********************************************************/ USE AdventureWorks GO   IF EXISTS       (SELECT *       FROM sysobjects       WHERE name = 'LaterOf'       AND xtype = 'FN'       ) BEGIN             DROP FUNCTION LaterOf END GO   CREATE FUNCTION LaterOf (       @Date1                              DATETIME,       @Date2                              DATETIME )   RETURNS DATETIME   AS BEGIN       DECLARE @ReturnDate     DATETIME         IF (@Date1 IS NULL AND @Date2 IS NULL)       BEGIN             SET @ReturnDate = NULL             GOTO EndOfFunction       END         ELSE IF (@Date1 IS NULL AND @Date2 IS NOT NULL)       BEGIN             SET @ReturnDate = @Date2             GOTO EndOfFunction       END         ELSE IF (@Date1 IS NOT NULL AND @Date2 IS NULL)       BEGIN             SET @ReturnDate = @Date1             GOTO EndOfFunction       END         ELSE       BEGIN             SET @ReturnDate = @Date1             IF @Date2 > @Date1                   SET @ReturnDate = @Date2             GOTO EndOfFunction       END         EndOfFunction:       RETURN @ReturnDate   END -- End Function GO   ---- Set Permissions --GRANT SELECT ON LaterOf TO UserRole1 --GRANT SELECT ON LaterOf TO UserRole2 --GO                                                                                             The interesting thing about this function is its simplicity and the built-in NULL handling functionality.  Its interesting, because it seems like something should already exist in SQL Server that does this.  From a different vantage point, if you create this functionality and it is easy to use (ideally, intuitively self-explanatory), you have made a successful contribution. Interesting is good.  Self-explanatory, or intuitive is FAR better.  Happy coding! Graeme

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• SQL SERVER – Number-Crunching with SQL Server – Exceed the Functionality of Excel

  - by Pinal Dave

  Imagine this. Your users have developed an Excel spreadsheet that extracts data from your SQL Server database, manipulates that data through the use of Excel formulas and, possibly, some VBA code which is then used to calculate P&L, hedging requirements or even risk numbers. Management comes to you and tells you that they need to get rid of the spreadsheet and that the results of the spreadsheet calculations need to be persisted on the database. SQL Server has a very small set of functions for analyzing data. Excel has hundreds of functions for analyzing data, with many of them focused on specific financial and statistical calculations. Is it even remotely possible that you can use SQL Server to replace the complex calculations being done in a spreadsheet? Westclintech has developed a library of functions that match or exceed the functionality of Excel’s functions and contains many functions that are not available in EXCEL. Their XLeratorDB library of functions contains over 700 functions that can be incorporated into T-SQL statements. XLeratorDB takes advantage of the SQL CLR architecture introduced in SQL Server 2005. SQL CLR permits managed code to be compiled into the database and run alongside built-in SQL Server functions like COUNT or SUM. The Westclintech developers have taken advantage of this architecture to bring robust analytical functions to the database. In our hypothetical spreadsheet, let’s assume that our users are using the YIELD function and that the data are extracted from a table in our database called BONDS. Here’s what the spreadsheet might look like. We go to column G and see that it contains the following formula. Obviously, SQL Server does not offer a native YIELD function. However, with XLeratorDB we can replicate this calculation in SQL Server with the following statement: SELECT *, wct.YIELD(CAST(GETDATE() AS date),Maturity,Rate,Price,100,Frequency,Basis) AS YIELD FROM BONDS This produces the following result. This illustrates one of the best features about XLeratorDB; it is so easy to use. Since I knew that the spreadsheet was using the YIELD function I could use the same function with the same calling structure to do the calculation in SQL Server. I didn’t need to know anything at all about the mechanics of calculating the yield on a bond. It was pretty close to cut and paste. In fact, that’s one way to construct the SQL. Just copy the function call from the cell in the spreadsheet and paste it into SMS and change the cell references to column names. I built the SQL for this query by starting with this. SELECT * ,YIELD(TODAY(),B2,C2,D2,100,E2,F2) FROM BONDS I then changed the cell references to column names. SELECT * --,YIELD(TODAY(),B2,C2,D2,100,E2,F2) ,YIELD(TODAY(),Maturity,Rate,Price,100,Frequency,Basis) FROM BONDS Finally, I replicated the TODAY() function using GETDATE() and added the schema name to the function name. SELECT * --,YIELD(TODAY(),B2,C2,D2,100,E2,F2) --,YIELD(TODAY(),Maturity,Rate,Price,100,Frequency,Basis) ,wct.YIELD(GETDATE(),Maturity,Rate,Price,100,Frequency,Basis) FROM BONDS Then I am able to execute the statement returning the results seen above. The XLeratorDB libraries are heavy on financial, statistical, and mathematical functions. Where there is an analog to an Excel function, the XLeratorDB function uses the same naming conventions and calling structure as the Excel function, but there are also hundreds of additional functions for SQL Server that are not found in Excel. You can find the functions by opening Object Explorer in SQL Server Management Studio (SSMS) and expanding the Programmability folder under the database where the functions have been installed. The  Functions folder expands to show 3 sub-folders: Table-valued Functions; Scalar-valued functions, Aggregate Functions, and System Functions. You can expand any of the first three folders to see the XLeratorDB functions. Since the wct.YIELD function is a scalar function, we will open the Scalar-valued Functions folder, scroll down to the wct.YIELD function and and click the plus sign (+) to display the input parameters. The functions are also Intellisense-enabled, with the input parameters displayed directly in the query tab. The Westclintech website contains documentation for all the functions including examples that can be copied directly into a query window and executed. There are also more one hundred articles on the site which go into more detail about how some of the functions work and demonstrate some of the extensive business processes that can be done in SQL Server using XLeratorDB functions and some T-SQL. XLeratorDB is organized into libraries: finance, statistics; math; strings; engineering; and financial options. There is also a windowing library for SQL Server 2005, 2008, and 2012 which provides functions for calculating things like running and moving averages (which were introduced in SQL Server 2012), FIFO inventory calculations, financial ratios and more, without having to use triangular joins. To get started you can download the XLeratorDB 15-day free trial from the Westclintech web site. It is a fully-functioning, unrestricted version of the software. If you need more than 15 days to evaluate the software, you can simply download another 15-day free trial. XLeratorDB is an easy and cost-effective way to start adding sophisticated data analysis to your SQL Server database without having to know anything more than T-SQL. Get XLeratorDB Today and Now! Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL Tagged: Excel

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• Does query plan optimizer works well with joined/filtered table-valued functions?

  - by smoothdeveloper

  In SQLSERVER 2005, I'm using table-valued function as a convenient way to perform arbitrary aggregation on subset data from large table (passing date range or such parameters). I'm using theses inside larger queries as joined computations and I'm wondering if the query plan optimizer work well with them in every condition or if I'm better to unnest such computation in my larger queries. Does query plan optimizer unnest table-valued functions if it make sense? If it doesn't, what do you recommend to avoid code duplication that would occur by manually unnesting them? If it does, how do you identify that from the execution plan? code sample: create table dbo.customers ( [key] uniqueidentifier , constraint pk_dbo_customers primary key ([key]) ) go /* assume large amount of data */ create table dbo.point_of_sales ( [key] uniqueidentifier , customer_key uniqueidentifier , constraint pk_dbo_point_of_sales primary key ([key]) ) go create table dbo.product_ranges ( [key] uniqueidentifier , constraint pk_dbo_product_ranges primary key ([key]) ) go create table dbo.products ( [key] uniqueidentifier , product_range_key uniqueidentifier , release_date datetime , constraint pk_dbo_products primary key ([key]) , constraint fk_dbo_products_product_range_key foreign key (product_range_key) references dbo.product_ranges ([key]) ) go . /* assume large amount of data */ create table dbo.sales_history ( [key] uniqueidentifier , product_key uniqueidentifier , point_of_sale_key uniqueidentifier , accounting_date datetime , amount money , quantity int , constraint pk_dbo_sales_history primary key ([key]) , constraint fk_dbo_sales_history_product_key foreign key (product_key) references dbo.products ([key]) , constraint fk_dbo_sales_history_point_of_sale_key foreign key (point_of_sale_key) references dbo.point_of_sales ([key]) ) go create function dbo.f_sales_history_..snip.._date_range ( @accountingdatelowerbound datetime, @accountingdateupperbound datetime ) returns table as return ( select pos.customer_key , sh.product_key , sum(sh.amount) amount , sum(sh.quantity) quantity from dbo.point_of_sales pos inner join dbo.sales_history sh on sh.point_of_sale_key = pos.[key] where sh.accounting_date between @accountingdatelowerbound and @accountingdateupperbound group by pos.customer_key , sh.product_key ) go -- TODO: insert some data -- this is a table containing a selection of product ranges declare @selectedproductranges table([key] uniqueidentifier) -- this is a table containing a selection of customers declare @selectedcustomers table([key] uniqueidentifier) declare @low datetime , @up datetime -- TODO: set top query parameters . select saleshistory.customer_key , saleshistory.product_key , saleshistory.amount , saleshistory.quantity from dbo.products p inner join @selectedproductranges productrangeselection on p.product_range_key = productrangeselection.[key] inner join @selectedcustomers customerselection on 1 = 1 inner join dbo.f_sales_history_..snip.._date_range(@low, @up) saleshistory on saleshistory.product_key = p.[key] and saleshistory.customer_key = customerselection.[key] I hope the sample makes sense. Much thanks for your help!

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• Implement two functions with the same name but different, non-covariant return types due to multiple abstract base classes

  - by user1508167

  If I have two abstract classes defining a pure virtual function with the same name, but different, non-covariant return types, how can I derive from these and define an implementation for both their functions? #include <iostream> class ITestA { public: virtual ~ITestA() {}; virtual float test() =0; }; class ITestB { public: virtual ~ITestB() {}; virtual bool test() =0; }; class C : public ITestA, public ITestB { public: /* Somehow implement ITestA::test and ITestB::test */ }; int main() { ITestA *a = new C(); std::cout << a->test() << std::endl; // should print a float, like "3.14" ITestB *b = dynamic_cast<ITestB *>(a); if (b) { std::cout << b->test() << std::endl; // should print "1" or "0" } delete(a); return 0; } As long as I don't call C::test() directly there's nothing ambiguous, so I think that it should work somehow and I guess I just didn't find the right notation yet. Or is this impossible, if so: Why?

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• F#: Advantages of converting top-level functions to member methods?

  - by J Cooper

  Earlier I requested some feedback on my first F# project. Before closing the question because the scope was too large, someone was kind enough to look it over and leave some feedback. One of the things they mentioned was pointing out that I had a number of regular functions that could be converted to be methods on my datatypes. Dutifully I went through changing things like let getDecisions hand = let (/=/) card1 card2 = matchValue card1 = matchValue card2 let canSplit() = let isPair() = match hand.Cards with | card1 :: card2 :: [] when card1 /=/ card2 -> true | _ -> false not (hasState Splitting hand) && isPair() let decisions = [Hit; Stand] let split = if canSplit() then [Split] else [] let doubleDown = if hasState Initial hand then [DoubleDown] else [] decisions @ split @ doubleDown to this: type Hand // ...stuff... member hand.GetDecisions = let (/=/) (c1 : Card) (c2 : Card) = c1.MatchValue = c2.MatchValue let canSplit() = let isPair() = match hand.Cards with | card1 :: card2 :: [] when card1 /=/ card2 -> true | _ -> false not (hand.HasState Splitting) && isPair() let decisions = [Hit; Stand] let split = if canSplit() then [Split] else [] let doubleDown = if hand.HasState Initial then [DoubleDown] else [] decisions @ split @ doubleDown Now, I don't doubt I'm an idiot, but other than (I'm guessing) making C# interop easier, what did that gain me? Specifically, I found a couple *dis*advantages, not counting the extra work of conversion (which I won't count, since I could have done it this way in the first place, I suppose, although that would have made using F# Interactive more of a pain). For one thing, I'm now no longer able to work with function "pipelining" easily. I had to go and change some |> chained |> calls to (some |> chained).Calls etc. Also, it seemed to make my type system dumber--whereas with my original version, my program needed no type annotations, after converting largely to member methods, I got a bunch of errors about lookups being indeterminate at that point, and I had to go and add type annotations (an example of this is in the (/=/) above). I hope I haven't come off too dubious, as I appreciate the advice I received, and writing idiomatic code is important to me. I'm just curious why the idiom is the way it is :) Thanks!

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• How can arguments to variadic functions be passed by reference in PHP?

  - by outis

  Assuming it's possible, how would one pass arguments by reference to a variadic function without generating a warning in PHP? We can no longer use the '&' operator in a function call, otherwise I'd accept that (even though it would be error prone, should a coder forget it). What inspired this is are old MySQLi wrapper classes that I unearthed (these days, I'd just use PDO). The only difference between the wrappers and the MySQLi classes is the wrappers throw exceptions rather than returning FALSE. class DBException extends RuntimeException {} ... class MySQLi_throwing extends mysqli { ... function prepare($query) { $stmt = parent::prepare($query); if (!$stmt) { throw new DBException($this->error, $this->errno); } return new MySQLi_stmt_throwing($this, $query, $stmt); } } // I don't remember why I switched from extension to composition, but // it shouldn't matter for this question. class MySQLi_stmt_throwing /* extends MySQLi_stmt */ { protected $_link, $_query, $_delegate; public function __construct($link, $query, $prepared) { //parent::__construct($link, $query); $this->_link = $link; $this->_query = $query; $this->_delegate = $prepared; } function bind_param($name, &$var) { return $this->_delegate->bind_param($name, $var); } function __call($name, $args) { //$rslt = call_user_func_array(array($this, 'parent::' . $name), $args); $rslt = call_user_func_array(array($this->_delegate, $name), $args); if (False === $rslt) { throw new DBException($this->_link->error, $this->errno); } return $rslt; } } The difficulty lies in calling methods such as bind_result on the wrapper. Constant-arity functions (e.g. bind_param) can be explicitly defined, allowing for pass-by-reference. bind_result, however, needs all arguments to be pass-by-reference. If you call bind_result on an instance of MySQLi_stmt_throwing as-is, the arguments are passed by value and the binding won't take. try { $id = Null; $stmt = $db->prepare('SELECT id FROM tbl WHERE ...'); $stmt->execute() $stmt->bind_result($id); // $id is still null at this point ... } catch (DBException $exc) { ... } Since the above classes are no longer in use, this question is merely a matter of curiosity. Alternate approaches to the wrapper classes are not relevant. Defining a method with a bunch of arguments taking Null default values is not correct (what if you define 20 arguments, but the function is called with 21?). Answers don't even need to be written in terms of MySQL_stmt_throwing; it exists simply to provide a concrete example.

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• Is it possible to view the "source" for a ksh function?

  - by stevec

  Our ksh environment defines several functions, which can be listed using then "functions" ksh function. Is it possible to see the definition (ie source code) for these functions? This seems like an obvious question, but I've tried all manner of parameters to the "functions" and "function" functions with no luck. Thanks, Steve

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• What is lambda expression.

  - by stackuser1

  What is lambda expression, any tutorial or link is avilable?

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• Using System.DateTime in a C# Lambda expression gives an exception

  - by Samantha J

  I tried to implement a suggestion that came up in another question: Stackoverflow question Snippet here: public static class StatusExtensions { public static IHtmlString StatusBox<TModel>( this HtmlHelper<TModel> helper, Expression<Func<TModel, RowInfo>> ex ) { var createdEx = Expression.Lambda<Func<TModel, DateTime>>( Expression.Property(ex.Body, "Created"), ex.Parameters ); var modifiedEx = Expression.Lambda<Func<TModel, DateTime>>( Expression.Property(ex.Body, "Modified"), ex.Parameters ); var a = "a" + helper.HiddenFor(createdEx) + helper.HiddenFor(modifiedEx); return new HtmlString( "Some things here ..." + helper.HiddenFor(createdEx) + helper.HiddenFor(modifiedEx) ); } } When implemented I am getting the following exception which I don't really understand. The exception points to the line starting with "var createdEx =" System.ArgumentException was unhandled by user code Message=Expression of type 'System.Nullable`1[System.DateTime]' cannot be used for return type 'System.DateTime' Source=System.Core StackTrace: Can anyone help me out and suggest what I could do to resolve the exception?

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• Summation using Lambda C# 3.0

  - by Newbie

  I have a small thing. public int GetSum(List<int> x) { foreach (int i in x) sum += i; return sum; } where x is a List of integers defined as List<int> l = new List<int>(); l.Add(4); l.Add(2); l.Add(5); l.Add(8); l.Add(6); and has been passed as GetSum(l) Is it possible to rewrite the above foreach loop using a lambda? Reason: I started looking into the lambda stuffs since yesterday and is interested to learn .. however simple it may be. Thanks.

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• "Cannot use fixed local inside lambda expression"

  - by JulianR

  I have an XNA 3.0 project that compiled just fine in VS2008, but that gives compile errors in VS2010 (with XNA 4.0 CTP). The error: Cannot use fixed local 'depthPtr' inside an anonymous method, lambda expression, or query expression depthPtr is a fixed float* into an array, that is used inside a Parallel.For lambda expression from System.Threading. As I said, this compiled and ran just fine on VS2008, but it does not on VS2010, even when targeting .NET 3.5. Has this changed in .NET 4.0, and even so, shouldn't it still compile when I choose .NET 3.5 as the target framework? Searching for the term "Cannot use fixed local" yields exactly one (useless) result, both in Google and Bing. If this has changed, what is the reason for this? I can imagine capturing a fixed pointer-type in a closure could get a bit weird, is that why? So I'm guessing this is bad practice? And before anyone asks: no, the use of pointers is not absolutely critical here. I would still like to know though :)

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• Change the for loop with lambda(C#3.0)

  - by Newbie

  Is it possible to do the same using Lambda for (int i = 0; i < objEntityCode.Count; i++) { options.Attributes[i] = new EntityCodeKey(); options.Attributes[i].EntityCode = objEntityCode[i].EntityCodes; options.Attributes[i].OrganizationCode = Constants.ORGANIZATION_CODE; } I mean to say to rewrite the statement using lambda. I tried with Enumerable.Range(0,objEntityCode.Count-1).Foreach(i=> { options.Attributes[i] = new EntityCodeKey(); options.Attributes[i].EntityCode = objEntityCode[i].EntityCodes; options.Attributes[i].OrganizationCode = Constants.ORGANIZATION_CODE; }); but not working I am using C#3.0

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• T-SQL Tuesday #24 : Dude, where's the rest of my procedure?

  - by AaronBertrand

  This month's T-SQL Tuesday is being hosted by Brad Schulz ( blog ) and the topic is one that should attract a lot of submissions: Procedures and Functions. Last week, I talked about the case against INFORMATION_SCHEMA views - I provided several examples where I feel the INFORMATION_SCHEMA views fall short of the catalog views, and expressed my belief that you are better off programming consistently against the catalog views all the time, instead of only when the INFORMATION_SCHEMA views fail. Having...(read more)

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• Looking for terminology for the relation of a subject and a predicate

  - by kostja

  While writing some predicates for collection filtering I have stumbled over the choice of the right words for the relation of the subject and the predicate (English is a foreign language for me). What I ended up writing was "Subjects matching this predicate..." This seems to be incorrect, since predicates are functions and not regular expressions. But saying "Subjects for which this predicate returns true..." sounds awkward to me as well.. So what would be the correct term?

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• Creating a property setter delegate

  - by Jim C

  I have created methods for converting a property lambda to a delegate: public static Delegate MakeGetter<T>(Expression<Func<T>> propertyLambda) { var result = Expression.Lambda(propertyLambda.Body).Compile(); return result; } public static Delegate MakeSetter<T>(Expression<Action<T>> propertyLambda) { var result = Expression.Lambda(propertyLambda.Body).Compile(); return result; } These work: Delegate getter = MakeGetter(() => SomeClass.SomeProperty); object o = getter.DynamicInvoke(); Delegate getter = MakeGetter(() => someObject.SomeProperty); object o = getter.DynamicInvoke(); but these won't compile: Delegate setter = MakeSetter(() => SomeClass.SomeProperty); setter.DynamicInvoke(new object[]{propValue}); Delegate setter = MakeSetter(() => someObject.SomeProperty); setter.DynamicInvoke(new object[]{propValue}); The MakeSetter lines fail with "The type arguments cannot be inferred from the usage. Try specifying the type arguments explicitly." Is what I'm trying to do possible? Thanks in advance.

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• I'm new to C++. Please Help me with the Linked List (What functions to add)?

  - by Igal

  DEAR All; Hi, I'm just beginner to C++; Please help me to understand: What functions should be in the Linked list class ? I think there should be overloaded operators << and ; Please help me to improve the code (style, errors, etc,) Thanks for advance. Igal. Please review the small code for the integer List (enclosed MyNODE.h and ListDriver1.cpp); MyNODE.h // This is my first attempt to write linked list. Igal Spector, June 2010. #include <iostream.h> #include <assert.h> //Forward Declaration of the classes: class ListNode; class TheLinkedlist; // Definition of the node (WITH IMPLEMENTATION !!!, without test drive): class ListNode{ friend class TheLinkedlist; public: // constructor: ListNode(const int& value, ListNode *next= 0); // note: no destructor, as this handled by TheLinkedList class. // accessor: return data in the node. // int Show() const {return theData;} private: int theData; //the Data ListNode* theNext; //points to the next node in the list. }; //Implementations: //constructor: inline ListNode::ListNode(const int &value,ListNode *next) :theData(value),theNext(next){} //end of ListNode class, now for the LL class: class TheLinkedlist { public: //constructors: TheLinkedlist(); virtual ~TheLinkedlist(); // Accessors: void InsertAtFront(const &); void AppendAtBack(const &); // void InOrderInsert(const &); bool IsEmpty()const;//predicate function void Print() const; private: ListNode * Head; //pointer to first node ListNode * Tail; //pointer to last node. }; //Implementation: //Default constructor inline TheLinkedlist::TheLinkedlist():Head(0),Tail(0) {} //Destructor inline TheLinkedlist::~TheLinkedlist(){ if(!IsEmpty()){ //list is not empty cout<<"\n\tDestroying Nodes"<<endl; ListNode *currentPointer=Head, *tempPtr; while(currentPointer != 0){ //Delete remaining Nodes. tempPtr=currentPointer; cout<<"The node: "<<tempPtr->theData <<" is Destroyed."<<endl<<endl; currentPointer=currentPointer->theNext; delete tempPtr; } Head=Tail = 0; //don't forget this, as it may be checked one day. } } //Insert the Node to the beginning of the list: void TheLinkedlist::InsertAtFront(const int& value){ ListNode *newPtr = new ListNode(value,Head); assert(newPtr!=0); if(IsEmpty()) //list is empty Head = Tail = newPtr; else { //list is NOT empty newPtr->theNext = Head; Head = newPtr; } } //Insert the Node to the beginning of the list: void TheLinkedlist::AppendAtBack(const int& value){ ListNode *newPtr = new ListNode(value, NULL); assert(newPtr!=0); if(IsEmpty()) //list is empty Head = Tail = newPtr; else { //list is NOT empty Tail->theNext = newPtr; Tail = newPtr; } } //is the list empty? inline bool TheLinkedlist::IsEmpty() const { return (Head == 0); } // Display the contents of the list void TheLinkedlist::Print()const{ if ( IsEmpty() ){ cout << "\n\t The list is empty!!"<<endl; return; } ListNode *tempPTR = Head; cout<<"\n\t The List is: "; while ( tempPTR != 0 ){ cout<< tempPTR->theData <<" "; tempPTR = tempPTR->theNext; } cout<<endl<<endl; } ////////////////////////////////////// The test Driver: //Driver test for integer Linked List. #include <iostream.h> #include "MyNODE.h" // main Driver int main(){ cout<< "\n\t This is the test for integer LinkedList."<<endl; const int arraySize=11, ARRAY[arraySize]={44,77,88,99,11,2,22,204,50,58,12}; cout << "\n\tThe array is: "; //print the numbers. for (int i=0;i<arraySize; i++) cout<<ARRAY[i]<<", "; TheLinkedlist list; //declare the list for(int index=0;index<arraySize;index++) list.AppendAtBack( ARRAY[index] );//create the list cout<<endl<<endl; list.Print(); //print the list return 0; //end of the program. }

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• Port to use CentOS init.d functions

  - by jcalfee314

  What are good equivalent centos commands using functions in /etc/init.d/functions such as daemon to perform the following tasks? STARTCMD='start-stop-daemon --start --exec /usr/sbin/swapspace --quiet --pidfile /var/run/swapspace.pid -- -d -p' STOPCMD='start-stop-daemon --stop --oknodo --quiet --pidfile /var/run/swapspace.pid' It looks like daemon will work for the start command and killproc is used for the stop command. . /etc/init.d/functions pushd /usr/sbin daemon --pidfile /var/run/swapspace.pid /usr/sbin/swapspace . /etc/init.d/functions killproc -p $(cat /var/run/swapspace.pid) Would the --oknodo be needed in the CentOS env (the swap file is really only boot-time)? "oknodo - Return exit status 0 instead of 1 if no actions are (would be) taken." I don't see quiet in daemon or killproc, I can't imagine that it would matter though. The original start-stop-daemon for swapspace seems to have both -p and --pidfile (the same command). That must be an error. Did I miss anything? Any idea why daemon not create the pid file?

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• SQL SERVER – Introduction to PERCENTILE_CONT() – Analytic Functions Introduced in SQL Server 2012

  - by pinaldave

  SQL Server 2012 introduces new analytical function PERCENTILE_CONT(). The book online gives following definition of this function: Computes a specific percentile for sorted values in an entire rowset or within distinct partitions of a rowset in Microsoft SQL Server 2012 Release Candidate 0 (RC 0). For a given percentile value P, PERCENTILE_DISC sorts the values of the expression in the ORDER BY clause and returns the value with the smallest CUME_DIST value (with respect to the same sort specification) that is greater than or equal to P. If you are clear with understanding of the function – no need to read further. If you got lost here is the same in simple words – it is lot like finding median with percentile value. Now let’s have fun following query: USE AdventureWorks GO SELECT SalesOrderID, OrderQty, ProductID, PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY ProductID) OVER (PARTITION BY SalesOrderID) AS MedianCont FROM Sales.SalesOrderDetail WHERE SalesOrderID IN (43670, 43669, 43667, 43663) ORDER BY SalesOrderID DESC GO The above query will give us the following result: You can see that I have used PERCENTILE_COUNT(0.5) in query, which is similar to finding median. Let me explain above diagram with little more explanation. The defination of median is as following: In case of Even Number of elements = In ordered list add the two digits from the middle and devide by 2 In case of Odd Numbers of elements = In ordered list select the digits from the middle I hope this example gives clear idea how PERCENTILE_CONT() works. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• System Variables, Stored Procedures or Functions for Meta Data

  - by BuckWoody

  Whenever you want to know something about SQL Server’s configuration, whether that’s the Instance itself or a database, you have a few options. If you want to know “dynamic” data, such as how much memory or CPU is consumed or what a particular query is doing, you should be using the Dynamic Management Views (DMVs) that you can read about here: http://msdn.microsoft.com/en-us/library/ms188754.aspx  But if you’re looking for how much memory is installed on the server, the version of the Instance, the drive letters of the backups and so on, you have other choices. The first of these are system variables. You access these with a SELECT statement, and they are useful when you need a discrete value for use, say in another query or to put into a table. You can read more about those here: http://msdn.microsoft.com/en-us/library/ms173823.aspx You also have a few stored procedures you can use. These often bring back a lot more data, pre-formatted for the screen. You access these with the EXECUTE syntax. It is a bit more difficult to take the data they return and get a single value or place the results in another table, but it is possible. You can read more about those here: http://msdn.microsoft.com/en-us/library/ms187961.aspx Yet another option is to use a system function, which you access with a SELECT statement, which also brings back a discrete value that you can use in a test or to place in another table. You can read about those here: http://msdn.microsoft.com/en-us/library/ms187812.aspx  By the way, many of these constructs simply query from tables in the master or msdb databases for the Instance or the system tables in a user database. You can get much of the information there as well, and there are even system views in each database to show you the meta-data dealing with structure – more on that here: http://msdn.microsoft.com/en-us/library/ms186778.aspx  Some of these choices are the only way to get at a certain piece of data. But others overlap – you can use one or the other, they both come back with the same data. So, like many Microsoft products, you have multiple ways to do the same thing. And that’s OK – just research what each is used for and how it’s intended to be used, and you’ll be able to select (pun intended) the right choice. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Looking At The Brother IntelliFax 1270 Printer Needed For Basic Office Functions

  When most people think of fax machines, they think of unclear documents filled with smudges and letters that are blurred. The Brother Intellifax 1270 printer and fax machine, however, dispels all neg... [Author: Ben Pate - Computers and Internet - March 21, 2010]

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• Gathering all data in single iteration vs using functions for readable code

  - by user828584

  Say I have an array of runners with which I need to find the tallest runner, the fastest runner, and the lightest runner. It seems like the most readable solution would be: runners = getRunners(); tallestRunner = getTallestRunner(runners); fastestRunner = getFastestRunner(runners); lightestRunner = getLightestRunner(runners); ..where each function iterates over the runners and keeps track of the largest height, greatest speed, and lowest weight. Iterating over the array three times, however, doesn't seem like a very good idea. It would instead be better to do: int greatestHeght, greatestSpeed, leastWeight; Runner tallestRunner, fastestRunner, lightestRunner; for(runner in runners){ if(runner.height > greatestHeight) { greatestHeight = runner.height; tallestRunner = runner; } if(runner.speed > ... } While this isn't too unreadable, it can get messy when there is more logic for each piece of information being extracted in the iteration. What's the middle ground here? How can I use only a single iteration while still keeping the code divided into logical units?

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• My PowerShell functions do not appear to be used

  - by Frank

  Hi there, I have a ps1 script in which I define 2 functions as such: function Invoke-Sql([string]$query) { Invoke-Sqlcmd -ServerInstance $Server -Database $DB -User $User -Password $Password -Query $query } function Get-Queued { Invoke-Sql "Select * From Comment where AwaitsModeration = 1" } I then call the ps1 file by typing it in (it's in a folder in the path, and autocompletion works) However, I cannot start using the functions. I am confused, because when I copy / paste the functions into the console, all is fine and they work. I also have a function defined in my profile, and it works. Where am I thinking wrong, why doesn't it work what I'm trying to do?

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• Is it possible to make a MS-SQL Scalar function do this?

  - by Hokken

  I have a 3rd party application that can call a MS-SQL scalar function to return some summary information from a table. I was able to return the summary values with a table-valued function, but the application won't utilize table-valued functions, so I'm kind of stuck. Here's a sample from the table: trackingNumber, projTaskAward, expenditureType, amount 1122, 12345-67-89, Supplies, 100 1122, 12345-67-89, Supplies, 150 1122, 12345-67-89, Supplies, 250 1122, 12345-67-89, Misc, 50 1122, 12345-67-89, Misc, 100 1122, 98765-43-21, General, 200 1122, 98765-43-21, Conference, 500 1122, 98765-43-21, Misc, 300 1122, 98765-43-21, Misc, 100 1122, 98765-43-21, Misc, 100 I want to summarize the amounts by projTaskAward & expenditureType, based on the trackingNumber. Here is the output I'm looking for: Proj/Task/Award: 12345-67-89 Expenditure Type: Supplies Total: 500 Proj/Task/Award: 12345-67-89 Expenditure Type: Misc Total: 150 Proj/Task/Award: 98765-43-21 Expenditure Type: General Total: 200 Proj/Task/Award: 98765-43-21 Expenditure Type: Conference Total: 500 Proj/Task/Award: 98765-43-21 Expenditure Type: Misc Total: 500 I'd appreciate any help anyone can give in steering me in the right direction.

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• SQL SERVER – Using RAND() in User Defined Functions (UDF)

  - by pinaldave

  Here is the question I received in email. “Pinal, I am writing a function where we need to generate random password. While writing T-SQL I faced following issue. Everytime I tried to use RAND() function in my User Defined Function I am getting following error: Msg 443, Level 16, State 1, Procedure RandFn, Line 7 Invalid use of a side-effecting operator ‘rand’ within a function. Here is the simplified T-SQL code of the function which I am using: CREATE FUNCTION RandFn() RETURNS INT AS BEGIN DECLARE @rndValue INT SET @rndValue = RAND() RETURN @rndValue END GO I must use UDF so is there any workaround to use RAND function in UDF.” Here is the workaround how RAND() can be used in UDF. The scope of the blog post is not to discuss the advantages or disadvantages of the function or random function here but just to show how RAND() function can be used in UDF. RAND() function is directly not allowed to use in the UDF so we have to find alternate way to use the same function. This can be achieved by creating a VIEW which is using RAND() function and use the same VIEW in the UDF. Here is the step by step instructions. Create a VIEW using RAND function. CREATE VIEW rndView AS SELECT RAND() rndResult GO Create a UDF using the same VIEW. CREATE FUNCTION RandFn() RETURNS DECIMAL(18,18) AS BEGIN DECLARE @rndValue DECIMAL(18,18) SELECT @rndValue = rndResult FROM rndView RETURN @rndValue END GO Now execute the UDF and it will just work fine and return random result. SELECT dbo.RandFn() GO In T-SQL world, I have noticed that there are more than one solution to every problem. Is there any better solution to this question? Please post that question as a comment and I will include it with due credit. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: technology

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