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Extending Currying: Partial Functions in Javascript

- by kerry

Last week I posted about function currying in javascript. This week I am taking it a step further by adding the ability to call partial functions. Suppose we have a graphing application that will pull data via Ajax and perform some calculation to update a graph. Using a method with the signature ‘updateGraph(id,value)’. To do this, we have do something like this: 1: for(var i=0;i<objects.length;i++) { 2: Ajax.request('/some/data',{id:objects[i].id},function(json) { 3: updateGraph(json.id, json.value); 4: } 5: } This works fine. But, using this method we need to return the id in the json response from the server. This works fine, but is not that elegant and increase network traffic. Using partial function currying we can bind the id parameter and add the second parameter later (when returning from the asynchronous call). To do this, we will need the updated curry method. I have added support for sending additional parameters at runtime for curried methods. 1: Function.prototype.curry = function(scope) { 2: scope = scope || window 3: var args = []; 4: for (var i=1, len = arguments.length; i < len; ++i) { 5: args.push(arguments[i]); 6: } 7: var m = this; 8: return function() { 9: for (var i=0, len = arguments.length; i < len; ++i) { 10: args.push(arguments[i]); 11: } 12: return m.apply(scope, args); 13: }; 14: } To partially curry this method we will call the curry method with the id parameter, then the request will callback on it with just the value. Any additional parameters are appended to the method call. 1: for(var i=0;i<objects.length;i++) { 2: var id=objects[i].id; 3: Ajax.request('/some/data',{id: id}, updateGraph.curry(id)); 4: } As you can see, partial currying gives is a very useful tool and this simple method should be a part of every developer’s toolbox.

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Calling functions from different classes

- by A Ron Hubbard Clevenger

I'm writing a program and I'm supposed to check and see if a certain object is in the list before I call it. I set up the contains() method which is supposed to use the equals() method of the Comparable interface I implemented on my Golfer class but it doesn't seem to call it (I put print statements in to check). I can't seem to figure out whats wrong with the code, the ArrayUnsortedList class I'm using to go through the list even uses the correct toString() method I defined in my Golfer class but for some reason it won't use the equals() method I implemented. //From "GolfApp.java" public class GolfApp{ ListInterface <Golfer>golfers = new ArraySortedList<Golfer> (20); Golfer golfer; //..*snip*.. if(this.golfers.contains(new Golfer(name,score))) System.out.println("The list already contains this golfer"); else{ this.golfers.add(this.golfer = new Golfer(name,score)); System.out.println("This golfer is already on the list"); } //From "ArrayUnsortedList.java" protected void find(T target){ location = 0; found = false; while (location < numElements){ if (list[location].equals(target)) //Where I think the problem is { found = true; return; } else location++; } } public boolean contains(T element){ find(element); return found; } //From "Golfer.java" public class Golfer implements Comparable<Golfer>{ //..irrelavant code sniped..// public boolean equals(Golfer golfer) { String thisString = score + ":" + name; String otherString = golfer.getScore() + ":" + golfer.getName() ; System.out.println("Golfer.equals() has bee called"); return thisString.equalsIgnoreCase(otherString); } public String toString() { return (score + ":" + name); } My main problem seems to be getting the find function of the ArrayUnsortedList to call my equals function in the find() part of the List but I'm not exactly sure why, like I said when I have it printed out it works with the toString() method I implemented perfectly. I'm almost positive the problem has to do with the find() function in the ArraySortedList not calling my equals() method. I tried using some other functions that relied on the find() method and got the same results.

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Retrieve input and output parameters for SQL stored procs and functions?

- by Darth Continent

For a given SQL stored proc or function, I'm trying to obtain its input and output parameters, where applicable, in a Winforms app I'm creating to browse objects and display their parameters and other attributes. So far I've discovered the SQL system function object_definition, which takes a given sysobjects.id and returns the text of that object; also discovered via search this post which describes extracting the parameters in the context of a app using the ADO.NET method DeriveParameters in conjunction with some caching for better performance; and for good measure found some helpful system stored procs from this earlier post on Hidden Features of SQL Server. I'm leaning towards implementing the DeriveParameters method in my C# app, since parsing the output of object_definition seems messy, and I haven't found a hidden feature in that post so far that would do the trick. Is DeriveParameters applicable to both functions and stored procs for purposes of retreiving their parameters, and if so, could someone please provide an example?

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Is a base class with shared fields and functions good design

- by eych

I've got a BaseDataClass with shared fields and functions Protected Shared dbase as SqlDatabase Protected Shared dbCommand as DBCommand ... //also have a sync object used by the derived classes for Synclock'ing Protected Shared ReadOnly syncObj As Object = New Object() Protected Shared Sub Init() //initializes fields, sets connections Protected Shared Sub CleanAll() //closes connections, disposes, etc. I have several classes that derive from this base class. The derived classes have all Shared functions that can be called directly from the BLL with no instantiation. The functions in these derived classes call the base Init(), call their specific stored procs, call the base CleanAll() and then return the results. So if I have 5 derived classes with 10 functions each, totaling 50 possible function calls, since they are all Shared, the CLR only calls one at a time, right? All calls are queued to wait until each Shared function completes. Is there a better design with having Shared functions in your DAL and still have base class functions? Or since I have a base class, is it better to move towards instance methods within the DAL?

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python function that returns a function from list of functions

- by thkang

I want to make following function: 1)input is a number. 2)functions are indexed, return a function whose index matches given number here's what I came up with: def foo_selector(whatfoo): def foo1(): return def foo2(): return def foo3(): return ... def foo999(): return #something like return foo[whatfoo] the problem is, how can I index the functions (foo#)? I can see functions foo1 to foo999 by dir(). however, dir() returns name of such functions, not the functions themselves. In the example, those foo-functions aren't doing anything. However in my program they perform different tasks and I can't automatically generate them. I write them myself, and have to return them by their name.

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How do I make lambda functions generic in Scala?

- by Electric Coffee

As most of you probably know you can define functions in 2 ways in scala, there's the 'def' method and the lambda method... making the 'def' kind generic is fairly straight forward def someFunc[T](a: T) { // insert body here what I'm having trouble with here is how to make the following generic: val someFunc = (a: Int) => // insert body here of course right now a is an integer, but what would I need to do to make it generic? val someFunc[T] = (a: T) => doesn't work, neither does val someFunc = [T](a: T) => Is it even possible to make them generic, or should I just stick to the 'def' variant?

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Origin of common list-processing function names

- by Heatsink

Some higher-order functions for operating on lists or arrays have been repeatedly adopted or reinvented. The functions map, fold[l|r], and filter are found together in several programming languages, such as Scheme, ML, and Python, that don't seem to have a common ancestor. I'm going with these three names to keep the question focused. To show that the names are not universal, here is a sampling of names for equivalent functionality in other languages. C++ has transform instead of map and remove_if instead of filter (reversing the meaning of the predicate). Lisp has mapcar instead of map, remove-if-not instead of filter, and reduce instead of fold (Some modern Lisp variants have map but this appears to be a derived form.) C# uses Select instead of map and Where instead of filter. C#'s names came from SQL via LINQ, and despite the name changes, their functionality was influenced by Haskell, which was itself influenced by ML. The names map, fold, and filter are widespread, but not universal. This suggests that they were borrowed from an influential source into other contemporary languages. Where did these function names come from?

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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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Virtualizing an Inline network appliance with VirtualBox (or VMWare)

- by Tzury Bar Yochay

My device, which is a Linux based IP in-liner is transparent to the network peripherals, that is, no IP address assigned to any of its interfaces. For the sake of the conversation, let's use ADSL connection as an example, while the device is inspecting the bi-directional traffic, the network is behaving same as if device was not there, attached to the wire (see Physical setup at the attached diagram). I wonder if I can enclosed that "device" within a Windows machine and have it operated virtually so it still seats inline between the ADSL router and the Windows netwroking interface by using virtual NICs, (or whatever their name is in windows), and inspecting the traffic, same as if it was on a separate physical device, the drawing under "Virtual Setup" in the attached diagram show what I am trying to achieve. Reading a bit on the VirtualBox docs, seems like binding the right side is relatively simple, perhaps I should have one network adapter set as Bridge Networking and VirtualBox will connect it to the physical NIC on the host machine, and network packets are exchanged directly, circumventing the host operating system's network stack (WinXP in my case). However, I have no idea how to achieve the left side of my diagram, which requires adding virtual NICs to windows and configure them correctly in a way to make that pipeline possible. I would appreciate any help. by the way, if that is not possible with VirtualBox but with other virtualization solution (e.g. VMWare), I would accept the other as well.

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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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Preserving Language across inline Calculated Members in SSAS

- by Tullo

Problem: I need to retrieve the language of a given cell from the cube. The cell is defined by code-generated MDX, which can have an arbitrary level of indirection as far as calculated members and sets go (defined in the WITH clause). SSAS appears to ignore the Language of the specified members when you declare a calculated member inline in the query. Example: The cube's default locale is 1033 (en-US) The cube contains a Calculated Measure called [Net Pounds] which is defined as [Net Amt], language=2057 (en-GB) The query requests this measure alongside an inline calculated measure which is simply an alias to the [Net Pounds] When used directly, the measure is formatted in the en-GB locale, but when aliased, the measure falls back to using the cube default of en-US. Here's what the query looks like: WITH MEMBER [Measures].[Pounds Indirect] AS [Measures].[Net Pounds] SELECT { [Measures].[Pounds Indirect], [Measures].[Net Pounds] } ON AXIS (0) FROM [Cube] CELL PROPERTIES language, value, formatted_value The query returns the expected two cells, but only uses the [Net Pounds] locale when used directly. Is there an option or switch somewhere in SSAS that will allow locale information to be visible in calculated members? I realise that it is possible to declare the inline calculated member in a particular locale, but this would involve extracting the locale from the tuple first, which (since the cube's member is isolated in the application's query schema) is unknown.

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Parsing XHTML with inline tags

- by user290796

Hi, I'm trying to parse an XHTML document using TBXML on the iPhone (although I would be happy to use either libxml2 or NSXMLParser if it would be easier). I need to extract the content of the body as a series of paragraphs and maintain the inline tags, for example: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"> <head> <title>Title</title> <link rel="stylesheet" href="css/style.css" type="text/css"/> <meta http-equiv="Content-Type" content="application/xhtml+xml; charset=utf-8"/> </head> <body> <div class="body"> <div> <h3>Title</h3> <p>Paragraph with <em>inline</em> tags</p> <img src="image.png" /> </div> </div> </body> </html> I need to extract the paragraph but maintain the <em>inline</em> content with the paragraph, all my testing so far has extracted that as a subelement without me knowing exactly where it fitted in the paragraph. Can anyone suggest a way to do this? Thanks.

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Align div inline

- by Rajeev

How to make the second div inline to the first div.I need the flash swf to appear next to the tds <html> <div style="display: inline"> <table style="table-layout:fixed;width:100%;"> <tr> <td width ="20%"> </td> </tr> <tr> <td width="20%"> 1.Can you view the image? </td> <td width="20%"> 1.Can you upload the image? </td> </tr> </table> </div> <div style="display: inline;"> <object width="100" height="100"> <embed src="image_tr.swf" width="250" height="250"> </embed> </object> </div>

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Inline form fields with labels placed on top

- by rcourtna

I can't believe I'm having to ask this, but I'm at my wit's end. I'm trying to display 2 form fields inline, but with the label for each field on the top. In ascii art: Label 1 Label 2 --------- --------- | | | | --------- --------- Should be pretty simple. <label for=foo>Label 1</label> <input type=text name=foo id=foo /> <label for=bar>Label 2</label> <input type=text name=bar id=bar /> This will get me: --------- --------- Label 1 | | Label 2 | | --------- --------- To get the labels on top of the boxes, I add display=block: <label for=foo style="display:block">Label 1</label> <input type=text name=foo id=foo /> <label for=bar style="display:block">Label 2</label> <input type=text name=bar id=bar /> After I do this, the labels are where I want them, but the form fields are no longer inline: Label 1 --------- | | --------- Label 2 --------- | | --------- I've been unable to find a way to wrap my html so the fields display inline. Can anyone help?

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Bootstrap inline button dropdown within <p> jumbotron

- by C.B.

Currently I have a jumbotron setup with some paragraph text, and I would like to stick a button dropdown inline with the text. Dropdown button <span class="btn-group"> <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown"> Button... <span class="caret"></span> </button> <ul class="dropdown-menu" role="menu"> <li><a href="#">Opt 1</a></li> <li><a href="#">Opt 2</a></li> </ul> </span> Jumbotron <div class="jumbotron"> <h1>Hello!</h1> <p>Welcome</p> <p>Another paragraph  </p> </div>  If the dropdown is within the <p> tag, it does not "dropdown" (but renders). If it is outside of the <p> tag it functions fine, but I would like it to be inline with the text and need the text to be in the <p> tag to get the style. Any ideas? Things to note -- If I replace the <span> tags with <div> tags, it will work fine within the <p> tags, but won't be inline.

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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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What triggered the popularity of lambda functions in modern mainstream programming languages?

- by Giorgio

In the last few years anonymous functions (AKA lambda functions) have become a very popular language construct and almost every major / mainstream programming language has introduced them or is planned to introduce them in an upcoming revision of the standard. Yet, anonymous functions are a very old and very well-known concept in Mathematics and Computer Science (invented by the mathematician Alonzo Church around 1936, and used by the Lisp programming language since 1958, see e.g. here). So why didn't today's mainstream programming languages (many of which originated 15 to 20 years ago) support lambda functions from the very beginning and only introduced them later? And what triggered the massive adoption of anonymous functions in the last few years? Is there some specific event, new requirement or programming technique that started this phenomenon? IMPORTANT NOTE The focus of this question is the introduction of anonymous functions in modern, main-stream (and therefore, maybe with a few exceptions, non functional) languages. Also, note that anonymous functions (blocks) are present in Smalltalk, which is not a functional language, and that normal named functions have been present even in procedural languages like C and Pascal for a long time. Please do not overgeneralize your answers by speaking about "the adoption of the functional paradigm and its benefits", because this is not the topic of the question.

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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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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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Extract inline images from Lotus Notes using Lotus Notes Java API

- by user1660645

I'm having issues to extract inline images that are pasted in the email body if the emails are sent from external email(like gmail for example) into the Lotus notes. The emails which are sent from Lotus Notes itself has no issues and I'm able to retrieve the inline images by using the document.generateXML() method and parsing through ['picture' xml element tag] the stream. My real concern is how to extract from the external emails(like gmail). I would really appreciate for your help and time on this. Thanks in advance!...

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