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• SQL SERVER – Puzzle to Win Print Book – Functions FIRST_VALUE and LAST_VALUE with OVER clause and ORDER BY

  - by pinaldave

  Some time an interesting feature and smart audience makes total difference at places. From last two days, I have been writing on SQL Server 2012 feature FIRST_VALUE and LAST_VALUE. Please read following post before I continue today as this question is based on the same. Introduction to FIRST_VALUE and LAST_VALUE Introduction to FIRST_VALUE and LAST_VALUE with OVER clause As a comment of the second post I received excellent question from Nilesh Molankar. He asks what will happen if we change few things in the T-SQL. I really like this question as this kind of questions will make us sharp and help us perform in critical situation in need. We recently publish SQL Server Interview Questions book. I promise that in future version of this book, we will for sure include this question. Instead of repeating his question, I am going to ask something very similar to his question. Let us first run following query (read yesterday’s blog post for more detail): USE AdventureWorks GO SELECT s.SalesOrderID,s.SalesOrderDetailID,s.OrderQty, FIRST_VALUE(SalesOrderDetailID) OVER (PARTITION BY SalesOrderID ORDER BY SalesOrderDetailID ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) FstValue, LAST_VALUE(SalesOrderDetailID) OVER (PARTITION BY SalesOrderID ORDER BY SalesOrderDetailID ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) LstValue FROM Sales.SalesOrderDetail s WHERE SalesOrderID IN (43670, 43669, 43667, 43663) ORDER BY s.SalesOrderID,s.SalesOrderDetailID,s.OrderQty GO Here is the resultset of the above query. Now let us change the ORDER BY clause of OVER clause in above query and see what is the new result. USE AdventureWorks GO SELECT s.SalesOrderID,s.SalesOrderDetailID,s.OrderQty, FIRST_VALUE(SalesOrderDetailID) OVER (PARTITION BY SalesOrderID ORDER BY OrderQty ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) FstValue, LAST_VALUE(SalesOrderDetailID) OVER (PARTITION BY SalesOrderID ORDER BY OrderQty ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) LstValue FROM Sales.SalesOrderDetail s WHERE SalesOrderID IN (43670, 43669, 43667, 43663) ORDER BY s.SalesOrderID,s.SalesOrderDetailID,s.OrderQty GO Now let us see the result and ready for interesting question: Puzzle You can see that row number 2, 3, 4, and 5 has same SalesOrderID = 43667. The FIRST_VALUE is 78 and LAST_VALUE is 77. Now if these function was working on maximum and minimum value they should have given answer as 77 and 80 respectively instead of 78 and 77. Also the value of FIRST_VALUE is greater than LAST_VALUE 77. Why? Explain in detail. Hint Let me give you a simple hint. Just for simplicity I have changed the order of columns selected in the SELECT and ORDER BY (at the end). This will not change resultset but just order of the columns as well order of the rows. However, the data remains the same. USE AdventureWorks GO SELECT s.OrderQty,s.SalesOrderID,s.SalesOrderDetailID, FIRST_VALUE(SalesOrderDetailID) OVER (PARTITION BY SalesOrderID ORDER BY OrderQty ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) FstValue, LAST_VALUE(SalesOrderDetailID) OVER (PARTITION BY SalesOrderID ORDER BY OrderQty ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) LstValue FROM Sales.SalesOrderDetail s WHERE SalesOrderID IN (43670, 43669, 43667, 43663) ORDER BY s.OrderQty,s.SalesOrderID,s.SalesOrderDetailID GO Above query returns following result: Now I am very sure all of you have figured out the solution. Here is the second hint – pay attention to row 2, 3, 4, and 10. Hint2 T-SQL Enhancements: FIRST_VALUE() and LAST_VALUE() MSDN: FIRST_VALUE and LAST_VALUE Rules Leave a comment with your detailed answer by Nov 15′s blog post. Open world-wide (where Amazon ships books) If you blog about puzzle’s solution and if you win, you win additional surprise gift as well. Prizes Print copy of my new book SQL Server Interview Questions Amazon|Flipkart If you already have this book, you can opt for any of my other books SQL Wait Stats [Amazon|Flipkart|Kindle] and SQL Programming [Amazon|Flipkart|Kindle]. 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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• Visual Studio Little Wonders: Quick Launch / Quick Access

  - by James Michael Hare

  Once again, in this series of posts I look at features of Visual Studio that may seem trivial, but can help improve your efficiency as a developer. The index of all my past little wonders posts can be found here. Well, my friends, this post will be a bit short because I’m in the middle of a bit of a move at the moment.  But, that said, I didn’t want to let the blog go completely silent this week, so I decided to add another Little Wonder to the list for the Visual Studio IDE. How often have you wanted to change an option or execute a command in Visual Studio, but can’t remember where the darn thing is in the menu, settings, etc.?  If so, Quick Launch in VS2012 (or Quick Access in VS2010 with the Productivity Power Tools extension) is just for you! Quick Launch / Quick Access – find a command or option quickly For those of you using Visual Studio 2012, Quick Launch is built right into the IDE at the top of the title bar, near the minimize, maximize, and close buttons: But do not despair if you are using Visual Studio 2010, you can get Quick Access from the Productivity Power Tools extension.  To do this, you can go to the extension manager: And then go to the gallery and search for Productivity Power Tools and install it.  If you don’t have VS2012 yet, then the Productivity Power Tools is the next best thing.  This extension updates VS2010 with features such as Quick Access, the Solution Navigator, searchable Add Reference Dialog, better tab wells, etc.  I highly recommend it! But back to the topic at hand!  In VS2012 Quick Launch is built into the IDE and can be accessed by clicking in the Quick Launch area of the title bar, or by pressing CTRL+Q.  If you have VS2010 with the PPT installed, though, it is called Quick Access and is accessible through View –> Quick Access: Regardless of which IDE you are using, the feature behaves mostly the same.  It allows you to search all of Visual Studio’s commands and options for a particular topic.  For example, let’s say you want to change from tabs to tabs expanded to spaces, but don’t remember where that option is buried.  You can bring up Quick Launch / Quick Access and type in “tabs”: And it brings up a list of all options on tabs, you can then choose the one appropriate to you and click on it and it will take you right there! A lot easier than diving through the options tree to find what you are looking for!  It also works on menu commands, for example if you can’t remember how to open the Output window: It shows you the menu items that will get you to the Output window, and (if applicable) the keyboard shortcuts.  Again, clicking on one of these will perform the action for you as well. There are also some tasks you can perform directly from Quick Launch / Quick Access.  For example, perhaps you are one of those people who like to have the line numbers in your editor (I do), so let’s bring up Quick Launch / Quick Access and type “line numbers”: And let’s select Turn Line Numbers On, and now our editor looks like: And Voila!  We have line numbers in VS2010.  You can do this in VS2012 too, but it takes you to the option settings instead of directly turning them off and on.  There are bound to be differences between the way the two editors organize settings and commands, but you get the point. So, as you can see, the Quick Launch / Quick Access feature in Visual Studio makes it easy to jump right to the options, commands, or tasks you are interested in without all the digging. Summary An IDE as powerful as Visual Studio has so many options and commands that it can be confusing to remember how to find and invoke them.  Quick Launch (Quick Access in VS2010 with Productivity Power Tools extension) is a quick and handy way to jump to any of these options, commands, or tasks quickly without having to remember in what menu or screen they are buried!  Technorati Tags: C#,CSharp,.NET,Little Wonders,Visual Studio,Quick Access,Quick Launch

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• Twice as long and half as long

  - by PointsToShare

  We are in a project and we hit some snags. What’s a snag? An activity that takes longer than expected. Actually it takes longer than the time assigned to it by an over pressed PM who accepts an impossible time table and tries his best to make it possible, but I digress (again!).  So we have snags and we also have the opposite. Let’s call these “cinches”. The question is: how does a combination of snags and cinches affect the project timeline? Well, there is no simple answer. It depends on the projects dependencies as we see in the PERT chart. If all the snags are in the critical path and all the cinches are elsewhere then the cinches don’t help at all. In fact any snag in the critical path will delay the project.  Conversely, a cinch in the critical path will expedite it. A snag outside the critical path might be serious enough to even change the critical path. Thus without the PERT chart, we cannot really tell. Still there is a principle involved – Time and speed are non-linear! Twice as long adds a full unit, half as long only takes ½ unit away. Let’s just investigate a simple project. It consists of two activities – S and C - each estimated to take a week. Alas, S is a snag and really needs twice the time allotted and – a sigh of relief – C is a cinch and will take half the time allotted, so everything is Hun-key-dory, or is it?  Even here the PERT chart is important. We have 2 cases: 1: S depends on C (or vice versa) as in when the two activities are assigned to one employee. Here the estimated time was 1 + 1 and the actual time was 2 + ½ and we are ½ week late or 25% late. 2: S and C are done in parallel. Here the estimated time was 1, but the actual time is 2 – we are a whole week or 100% late. Let’s change the equation a little. S need 1.5 and C needs .5 so in case 1, we have the loss fully compensated by the gain, but in case 2 we are still behind. There are cases where this really makes no difference. This is when the critical path is not affected and we have enough slack in the other paths to counteract the difference between its snags and cinches – Let’s call this difference DSC. So if the slack is greater than DSC the project will not suffer. Conclusion: There is no general rule about snags and cinches. We need to examine each case within its project, still as we saw in the 4 examples above; the snag is generally more powerful than the cinch. Long live Murphy! That’s All Folks

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• Type checking and recursive types (Writing the Y combinator in Haskell/Ocaml)

  - by beta

  When explaining the Y combinator in the context of Haskell, it's usually noted that the straight-forward implementation won't type-check in Haskell because of its recursive type. For example, from Rosettacode [1]: The obvious definition of the Y combinator in Haskell canot be used because it contains an infinite recursive type (a = a -> b). Defining a data type (Mu) allows this recursion to be broken. newtype Mu a = Roll { unroll :: Mu a -> a } fix :: (a -> a) -> a fix = \f -> (\x -> f (unroll x x)) $ Roll (\x -> f (unroll x x)) And indeed, the “obvious” definition does not type check: ?> let fix f g = (\x -> \a -> f (x x) a) (\x -> \a -> f (x x) a) g <interactive>:10:33: Occurs check: cannot construct the infinite type: t2 = t2 -> t0 -> t1 Expected type: t2 -> t0 -> t1 Actual type: (t2 -> t0 -> t1) -> t0 -> t1 In the first argument of `x', namely `x' In the first argument of `f', namely `(x x)' In the expression: f (x x) a <interactive>:10:57: Occurs check: cannot construct the infinite type: t2 = t2 -> t0 -> t1 In the first argument of `x', namely `x' In the first argument of `f', namely `(x x)' In the expression: f (x x) a (0.01 secs, 1033328 bytes) The same limitation exists in Ocaml: utop # let fix f g = (fun x a -> f (x x) a) (fun x a -> f (x x) a) g;; Error: This expression has type 'a -> 'b but an expression was expected of type 'a The type variable 'a occurs inside 'a -> 'b However, in Ocaml, one can allow recursive types by passing in the -rectypes switch: -rectypes Allow arbitrary recursive types during type-checking. By default, only recursive types where the recursion goes through an object type are supported. By using -rectypes, everything works: utop # let fix f g = (fun x a -> f (x x) a) (fun x a -> f (x x) a) g;; val fix : (('a -> 'b) -> 'a -> 'b) -> 'a -> 'b = <fun> utop # let fact_improver partial n = if n = 0 then 1 else n*partial (n-1);; val fact_improver : (int -> int) -> int -> int = <fun> utop # (fix fact_improver) 5;; - : int = 120 Being curious about type systems and type inference, this raises some questions I'm still not able to answer. First, how does the type checker come up with the type t2 = t2 -> t0 -> t1? Having come up with that type, I guess the problem is that the type (t2) refers to itself on the right side? Second, and perhaps most interesting, what is the reason for the Haskell/Ocaml type systems to disallow this? I guess there is a good reason since Ocaml also will not allow it by default even if it can deal with recursive types if given the -rectypes switch. If these are really big topics, I'd appreciate pointers to relevant literature. [1] http://rosettacode.org/wiki/Y_combinator#Haskell

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• SQL SERVER – Solution – User Not Able to See Any User Created Object in Tables – Security and Permissions Issue

  - by pinaldave

  There is an old quote “A Picture is Worth a Thousand Words”. I believe this quote immensely. Quite often I get phone calls that something is not working if I can help. My reaction is in most of the cases, I need to know more, send me exact error or a screenshot. Until and unless I see the error or reproduce the scenario myself I prefer not to comment. Yesterday I got a similar phone call from an old friend, where he was not sure what is going on. Here is what he said. “When I try to connect to SQL Server, it lets me connect just fine as well let me open and explore the database. I noticed that I do not see any user created instances but when my colleague attempts to connect to the server, he is able to explore the database as well see all the user created tables and other objects. Can you help me fix it? “ My immediate reaction was he was facing security and permission issue. However, to make the same recommendation I suggested that he send me a screenshot of his own SSMS and his friend’s SSMS. After carefully looking at both the screenshots, I was very confident about the issue and we were able to resolve the issue. Let us reproduce the same scenario and many there is some learning for us. Issue: User not able to see user created objects First let us see the image of my friend’s SSMS screen. (Recreated on my machine) Now let us see my friend’s colleague SSMS screen. (Recreated on my machine) You can see that my friend could not see the user tables but his colleague was able to do the same for sure. Now I believed it was a permissions issue. Further to this I asked him to send me another image where I can see the various permissions of the user in the database. My friends screen My friends colleagues screen This indeed proved that my friend did not have access to the AdventureWorks database and because of the same he was not able to access the database. He did have public access which means he will have similar rights as guest access. However, their SQL Server had followed my earlier advise on having limited access for guest access, which means he was not able to see any user created objects. My next question was to validate what kind of access my friend’s colleague had. He replied that the colleague is the admin of the server. I suggested that if my friend was suppose to have admin access to the database, he should request of having admin access to his colleague. My friend promptly asked for the same to his colleague and on following screen he added him as an admin. You can do the same using following T-SQL script as well. USE [AdventureWorks2012] GO ALTER ROLE [db_owner] ADD MEMBER [testguest] GO Once my friend was admin he was able to access all the user objects just like he was expecting. Please note, this complete exercise was done on a development server. One should not play around with security on live or production server. Security is such an issue, which should be left with only senior administrator of the server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Security, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• When should I use a Process Model versus a Use Case?

  - by Dave Burke

  This Blog entry is a follow on to https://blogs.oracle.com/oum/entry/oum_is_business_process_and and addresses a question I sometimes get asked…..i.e. “when I am gathering requirements on a Project, should I use a Process Modeling approach, or should I use a Use Case approach?” Not surprisingly, the short answer is “it depends”! Let’s take a scenario where you are working on a Sales Force Automation project. We’ll call the process that is being implemented “Lead-to-Order”. I would typically think of this type of project as being “Process Centric”. In other words, the focus will be on orchestrating a series of human and system related tasks that ultimately deliver value to the business in a cost effective way. Put in even simpler terms……implement an automated pre-sales system. For this type of (Process Centric) project, requirements would typically be gathered through a series of Workshops where the focal point will be on creating, or confirming, the Future-State (To-Be) business process. If pre-defined “best-practice” business process models exist, then of course they could and should be used during the Workshops, but even in their absence, the focus of the Workshops will be to define the optimum series of Tasks, their connections, sequence, and dependencies that will ultimately reflect a business process that meets the needs of the business. Now let’s take another scenario. Assume you are working on a Content Management project that involves automating the creation and management of content for User Manuals, Web Sites, Social Media publications etc. Would you call this type of project “Process Centric”?.......well you could, but it might also fall into the category of complex configuration, plus some custom extensions to a standard software application (COTS). For this type of project it would certainly be worth considering using a Use Case approach in order to 1) understand the requirements, and 2) to capture the functional requirements of the custom extensions. At this point you might be asking “why couldn’t I use a Process Modeling approach for my Content Management project?” Well, of course you could, but you just need to think about which approach is the most effective. Start by analyzing the types of Tasks that will eventually be automated by the system, for example: Best Suited To? Task Name Process Model Use Case Notes Manage outbound calls Ö A series of linked human and system tasks for calling and following up with prospects Manage content revision Ö Updating the content on a website Update User Preferences Ö Updating a users display preferences Assign Lead Ö Reviewing a lead, then assigning it to a sales person Convert Lead to Quote Ö Updating the status of a lead, and then converting it to a sales order As you can see, it’s not an exact science, and either approach is viable for the Tasks listed above. However, where you have a series of interconnected Tasks or Activities, than when combined, deliver value to the business, then that would be a good indicator to lead with a Process Modeling approach. On the other hand, when the Tasks or Activities in question are more isolated and/or do not cross traditional departmental boundaries, then a Use Case approach might be worth considering. Now let’s take one final scenario….. As you captured the To-Be Process flows for the Sales Force automation project, you discover a “Gap” in terms of what the client requires, and what the standard COTS application can provide. Let’s assume that the only way forward is to develop a Custom Extension. This would now be a perfect opportunity to document the functional requirements (behind the Gap) using a Use Case approach. After all, we will be developing some new software, and one of the most effective ways to begin the Software Development Lifecycle is to follow a Use Case approach. As always, your comments are most welcome.

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• Calling Matlab's MLApp.MLAppClass.FEval from F#

  - by Matthew

  Matlab provides a COM interface that supports remote execution of arbitrary functions (and code snippets). In particular, it has an Feval method that calls a given Matlab function. The third parameter to this method, pvarArgOut, has COM type VARIANT*, and appears in the Visual Studio F# editor as an argument of type: pvarArgOut: byref<obj> The following code calls interp1, which in Matlab returns a matrix (i.e. 2D double array) result, as is normal for most Matlab functions. let matlab = new MLApp.MLAppClass() let vector_to_array2d (v : vector) = Array2D.init v.Length 1 (fun i j -> v.[i]) let interp1 (xs : vector) (ys : vector) (xi : vector) = let yi : obj = new obj() matlab.Feval("interp1", 1, ref yi, vector_to_array2d xs, vector_to_array2d ys, vector_to_array2d xi) yi :?> float[,] This code compiles fine, but when calling interp1, I get a COM exception: A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in mscorlib.dll A first chance exception of type 'System.Runtime.InteropServices.COMException' occurred in mscorlib.dll An unhandled exception of type 'System.Runtime.InteropServices.COMException' occurred in mscorlib.dll Additional information: Invalid callee. (Exception from HRESULT: 0x80020010 (DISP_E_BADCALLEE)) I get the same error whether initialize yi with a new obj, a new Array2D, or null. How does F# translate VARIANT output arguments?

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• F# Powerpack's Metadata doesn't recognize FSharp.Core as an F# library

  - by Nathan Sanders

  Here's my test code to isolate the problem: open Microsoft.FSharp.Metadata [<EntryPoint>] let main args = let core = FSharpAssembly.FromFile @"C:\Program Files\FSharp-2.0.0.0\\bin\FSharp.Core.dll" let core2 = FSharpAssembly.FSharpLibrary let core3 = System.AppDomain.CurrentDomain.GetAssemblies() |> Seq.find (fun a -> a.FullName.Contains "Core") |> FSharpAssembly.FromAssembly core.Entities |> Seq.iter (printfn "%A") 0 All three lets should give me the same FSharpAssembly. Instead, all 3 throw an exception that FSharp.Core is not an F# assembly (details below, re-formatted for readability). Two more clues: Using the core3 method, I get the same error for the test F# assembly itself I don't get the error at FSI after doing #r "@C:\Program Files...\FSharp.Powerpack.Metadata.dll". Any ideas? I'm using Visual Studio 2008, F# 2.0 and F# Powerpack 2.0.0.0 (May 20, 2010) release on an oldish XP VM, I think it's updated to SP3 though. (I got the error this morning with Powerpack 1.9.9.9, so I upgraded to 2.0.0.0. I thought that if 1.9.9.9 doesn't recognise F#'s 2.0.0.0's assemblies, then maybe bugfixes in Powerpack 2.0.0.0 would help.) Unhandled Exception: System.TypeInitializationException: The type initializer for 'Microsoft.FSharp.Metadata.AssemblyLoader' threw an exception. ---> System.TypeInitializationException: The type initializer for '<StartupCode$FSharp-PowerPack-Metadata>.$Metadata' threw an exception. ---> System.ArgumentException: could not produce an FSharpAssembly object for the assembly 'FSharp.Core' because this is not an F# assembly Parameter name: name at Microsoft.FSharp.Metadata.AssemblyLoader.Add(String name,Assembly assembly) at <StartupCode$FSharp-PowerPack-Metadata>.$Metadata..cctor() --- End of inner exception stack trace --- at Microsoft.FSharp.Metadata.AssemblyLoader..cctor() --- End of inner exception stack trace --- at Microsoft.FSharp.Metadata.AssemblyLoader.Get(Assembly assembly) at Microsoft.FSharp.Metadata.FSharpAssembly.FromAssembly(Assembly assembly) at Program.main(String[] args) in C:\Documents an...\FSMetadataTest\Program.fs:line 11 Press any key to continue . . .

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• Mutation Problem - Clojure

  - by Silanglaya Valerio

  having trouble changing an element of my function represented as a list. code for random function: (defn makerandomtree-10 [pc maxdepth maxwidth fpx ppx] (if-let [output (if (and (< (rand) fpx) (> maxdepth 0)) (let [head (nth operations (rand-int (count operations))) children (doall (loop[function (list) width maxwidth] (if (pos? width) (recur (concat function (list (makerandomtree-10 pc (dec maxdepth) (+ 2 (rand-int (- maxwidth 1))) fpx ppx))) (dec width)) function)))] (concat (list head) children)) (if (and (< (rand) ppx) (>= pc 0)) (nth parameters (rand-int (count parameters))) (rand-int 100)))] output )) I will provide also a mutation function, which is still not good enough. I need to be able to eval my statement, so the following is still insufficient. (defn mutate-5 "chooses a node changes that" [function pc maxwidth pchange] (if (< (rand) pchange) (let [output (makerandomtree-10 pc 3 maxwidth 0.5 0.6)] (if (seq? output) output (list output))) ;mutate the children of root ;declare an empty accumulator list, with root as its head (let [head (list (first function)) children (loop [acc(list) walker (next function)] (println "----------") (println walker) (println "-----ACC-----") (println acc) (if (not walker) acc (if (or (seq? (first function)) (contains? (set operations) (first function))) (recur (concat acc (mutate-5 walker pc maxwidth pchange)) (next walker)) (if (< (rand) pchange) (if (some (set parameters) walker) (recur (concat acc (list (nth parameters (rand-int (count parameters))))) (if (seq? walker) (next walker) nil)) (recur (concat acc (list (rand-int 100))) (if (seq? walker) (next walker) nil))) (recur acc (if (seq? walker) (next walker) nil)))) ))] (concat head (list children))))) (side note: do you have any links/books for learning clojure?)

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• Max Value of a Multiway Tree in OCaml

  - by Trigork

  I'm an IT Student and kind of a newbie to OCaml Recently, studying for an exam I found this exercise. Given: type 'a tree = Tree of 'a * 'a tree list Define a function mtree : 'a tree -'a, that returns the greatest value of all the nodes in a multiway tree, following the usual order relation in OCaml (<=) I've come to do something like this below, which, of course, is not working. let rec mtree (Tree (r, sub)) = let max_node (Tree(a, l1)) (Tree(b, l2)) = if a >= b then (Tree(a, l1)) else (Tree(b, l2)) in List.fold_left max_node r sub;; After reading an answer to this I'm posting the fixed code. let rec mtree (Tree(r,sub)) = let max_node (Tree(a, l1)) (Tree(b, l2)) = if a >= b then a else b in List.fold_left (max_node) r (List.map mtree sub);; The idea is the same, fold the list comparing the nodes making use of my local function to do so and travel through the tree by calling the function itself over the nodes lists of the consecutive levels. Is still not working, though. Now complains about max_node in the fold_left part. Error: This expression has type 'a tree -> 'a tree -> 'a but an expression was expected of type 'a tree -> 'a tree -> 'a tree And here I'm definitely lost because I can't see why does it expects to return an 'a tree

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• Reading Xml with XmlReader in C#

  - by Gloria Huang

  I'm trying to read the following Xml document as fast as I can and let additional classes manage the reading of each sub block. <ApplicationPool><Accounts><Account><NameOfKin></NameOfKin><StatementsAvailable><Statement></Statement></StatementsAvailable></Account></Accounts></ApplicationPool> I can't seem to format the above nicely :( However, I'm trying to use the XmlReader object to read each Account and subsequently the "StatementsAvailable". Do you suggest using XmlReader.Read and check each element and handle it? I've thought of seperating my classes to handle each node properly. So theres an AccountBase class that accepts a XmlReader instance that reads the NameOfKin and several other properties about the account. Then I was wanting to interate through the Statements and let another class fill itself out about the Statement (and subsequently add it to an IList). Thus far I have the "per class" part done by doing XmlReader.ReadElementString() but I can't workout how to tell the pointer to move to the StatementsAvailable element and let me iterate through them and let another class read each of those proeprties. Sounds easy!

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• How do you pass .net objects values around in F#?

  - by Russell

  I am currently learning F# and functional programming in general (from a C# background) and I have a question about using .net CLR objects during my processing. The best way to describe my problem will be to give an example: let xml = new XmlDocument() |> fun doc -> doc.Load("report.xml"); doc let xsl = new XslCompiledTransform() |> fun doc -> doc.Load("report.xsl"); doc let transformedXml = new MemoryStream() |> fun mem -> xsl.Transform(xml.CreateNavigator(), null, mem); mem This code transforms an XML document with an XSLT document using .net objects. Note XslCompiledTransform.Load works on an object, and returns void. Also the XslCompiledTransform.Transform requires a memorystream object and returns void. The above strategy used is to add the object at the end (the ; mem) to return a value and make functional programming work. When we want to do this one after another we have a function on each line with a return value at the end: let myFunc = new XmlDocument("doc") |> fun a -> a.Load("report.xml"); a |> fun a -> a.AppendChild(new XmlElement("Happy")); a Is there a more correct way (in terms of functional programming) to handle .net objects and objects that were created in a more OO environment? The way I returned the value at the end then had inline functions everywhere feels a bit like a hack and not the correct way to do this. Any help is greatly appreciated!

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• F# Active Pattern List.filter or equivalent

  - by akaphenom

  I have a records of types type tradeLeg = { id : int ; tradeId : int ; legActivity : LegActivityType ; actedOn : DateTime ; estimates : legComponents ; entryType : ShareOrDollarBased ; confirmedPrice: DollarsPerShare option; actuals : legComponents option ; type trade = { id : int ; securityId : int ; ricCode : string ; tradeActivity : TradeType ; enteredOn : DateTime ; closedOn : DateTime ; tradeLegs : tradeLeg list ; } Obviously the tradeLegs are a type off of a trade. A leg may be settled or unsettled (or unsettled but price confirmed) - thus I have defined the active pattern: let (|LegIsSettled|LegIsConfirmed|LegIsUnsettled|) (l: tradeLeg) = if Helper.exists l.actuals then LegIsSettled elif Helper.exists l.confirmedPrice then LegIsConfirmed else LegIsUnsettled and then to determine if a trade is settled (based on all legs matching LegIsSettled pattern: let (|TradeIsSettled|TradeIsUnsettled|) (t: trade) = if List.exists ( fun l -> match l with | LegIsSettled -> false | _ -> true) t.tradeLegs then TradeIsSettled else TradeIsUnsettled I can see some advantages of this use of active patterns, however i would think there is a more efficient way to see if any item of a list either matches (or doesn't) an actie pattern without having to write a lambda expression specifically for it, and using List.exist. Question is two fold: is there a more concise way to express this? is there a way to abstract the functionality / expression (fun l - match l with | LegIsSettled - false | _ - true) Such that let itemMatchesPattern pattern item = match item with | pattern -> true | _ -> false such I could write (as I am reusing this design-pattern): let curriedItemMatchesPattern = itemMatchesPattern LegIsSettled if List.exists curriedItemMatchesPattern t.tradeLegs then TradeIsSettled else TradeIsUnsettled Thoughts?

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• How can I do batch image processing with ImageJ in Java or clojure?

  - by Robert McIntyre

  I want to use ImageJ to do some processing of several thousand images. Is there a way to take any general imageJ plugin and apply it to hundreds of images automatically? For example, say I want to take my thousand images and apply a polar transformation to each--- A polar transformation plugin for ImageJ can be found here: http://rsbweb.nih.gov/ij/plugins/polar-transformer.html Great! Let's use it. From: [http://albert.rierol.net/imagej_programming_tutorials.html#How%20to%20automate%20an%20ImageJ%20dialog] I find that I can apply a plugin using the following: (defn x-polar [imageP] (let [thread (Thread/currentThread) options ""] (.setName thread "Run$_polar-transform") (Macro/setOptions thread options) (IJ/runPlugIn imageP "Polar_Transformer" ""))) This is good because it suppresses the dialog which would otherwise pop up for every image. But running this always brings up a window containing the transformed image, when what I want is to simply return the transformed image. The stupidest way to do what I want is to just close the window that comes up and return the image which it was displaying. Does what I want but is absolutely retarded: (defn x-polar [imageP] (let [thread (Thread/currentThread) options ""] (.setName thread "Run$_polar-transform") (Macro/setOptions thread options) (IJ/runPlugIn imageP "Polar_Transformer" "") (let [return-image (IJ/getImage)] (.hide return-image) return-image))) I'm obviously missing something about how to use imageJ plugins in a programming context. Does anyone know the right way to do this? Thanks, --Robert McIntyre

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• Submit WordPress form password programmatically

  - by songdogtech

  How can I let a user access a WordPress protected page with a URL that will submit the password in the form below? I want to be able to let a user get to a password protected WordPress page without needing to type the password, so when they go to the page, the password is submitted by a POST URL on page load. This not intended to be secure in any respect; I'll need to hardcode the password in the URL and the PHP. It's just for simplicity for the user, and once they're in, the cookie will let them in for 10 more days. I will select the particular user with separate PHP function that determines their IP or WordPress login status. I used Wireshark to find the POST string: post_password=mypassword&Submit=Submit but using this URL mydomain.com/wp-pass.php?post_password=mypassword&Submit=Submit gives me a blank page. This is the form: <form action="http://mydomain.com/wp-pass.php" method="post"> Password: <input name="post_password" type="password" size="20" /> <input type="submit" name="Submit" value="Submit" /></form> This is wp-pass.php: <?php require( dirname(__FILE__) . '/wp-load.php'); if ( get_magic_quotes_gpc() ) $_POST['post_password'] = stripslashes($_POST['post_password']); setcookie('wp-postpass_' . COOKIEHASH, $_POST['post_password'], time() + 864000, COOKIEPATH); wp_safe_redirect(wp_get_referer()); ?> What am I doing wrong? Or is there a better way to let a user into a password protected page automatically?

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• how to access a type defined in one .ml file in another .ml file

  - by user339261

  Hi, I m very new to ocaml and i m facing the problem below, In a.ml a record type t is defined and is also defined transparently in a.mli, i.e. in d interface so that the type definition is available to all other files. a.ml also has a function, func, which returns a list of t. Now in another file, b.ml i m calling func, now obviously ocaml compiler wud nt be able to infer d type of objects stored in d list, for compiler its just a list. so in b.ml, i hav something like dis, let tlist = A.func in let vart = List.hd tlist in printf "%s\n" vart.name (name is a field in record t) Now here i get a compiler error sayin "Unbound record field label name" which makes sense as compiler can't infer d type of vart. my first question: how do I explicitly provide d type of vart as t here? i tried doing "let vart:A.t = " but got the same error. I also tried creating another function to fetch the first element of d list and mentioning return type as A.t, but then i got the "Unbound value A.t". I did this: let firstt = function [] - 0 | x :: _ - A.t x ;; The problem is compiler is unable to recognize A.t (a type) in b.ml but is able to recognize function A.func. If I remove A.t from the b.ml, i don'get any compiler errors. Please help, its urgent work. Thanks in advance! ~Tarun

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• Which languages support *recursive* function literals / anonymous functions?

  - by Hugh Allen

  It seems quite a few mainstream languages support function literals these days. They are also called anonymous functions, but I don't care if they have a name. The important thing is that a function literal is an expression which yields a function which hasn't already been defined elsewhere, so for example in C, &printf doesn't count. EDIT to add: if you have a genuine function literal expression <exp>, you should be able to pass it to a function f(<exp>) or immediately apply it to an argument, ie. <exp>(5). I'm curious which languages let you write function literals which are recursive. Wikipedia's "anonymous recursion" article doesn't give any programming examples. Let's use the recursive factorial function as the example. Here are the ones I know: JavaScript / ECMAScript can do it with callee: function(n){if (n<2) {return 1;} else {return n * arguments.callee(n-1);}} it's easy in languages with letrec, eg Haskell (which calls it let): let fac x = if x<2 then 1 else fac (x-1) * x in fac and there are equivalents in Lisp and Scheme. Note that the binding of fac is local to the expression, so the whole expression is in fact an anonymous function. Are there any others?

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• GoDaddy Subdomain Hosting Issue/Question with Disk Access (C#/ASP.NET 3.5)

  - by Vogel

  This isn't a very complicated scenario really, but as I start to type out the problem I'm realizing how convoluted it can become textually. Let me try and be very clear: First, the set up... I have a C#/ASP.NET web application that is publicly facing on my main domain (www), let's call it www.mysite.com. Nothing fancy, just a front-end that connects to SQL to display records. Then, I have a second C#/ASP.NET web application that is secured using forms authentication running on a subdomain, let's call it admin.mysite.com. This is a very light-weight CMS system to administer the public site. Now, the problem... Both of these sites run fine for basic tasks, however, my problem arises when I try to gain access to the file system for uploading. GoDaddy requires subdomains to run as a virtual directories under the main application in IIS (so the subdomains actually resolve/re-direct to www.mysite.com/admin when you type in admin.mysite.com), but because of this I am unable to write to my website root from the subfolder. Let me explain a little more... The CMS system (running as a virtual directory) gives the admin the ability to upload photos for display on the main site, the target folder of which is www.mysite.com/images - when attempting disk access from the root app, I am able to write to the virtual directory, but cannot do the opposite -- that is, write to the root from the virtual directory, getting security violations. If I can only upload to the /admin/ virtual directory, the entire point is moot because it's a secured folder that the public can't see! The only solution I can think of is to upload the files to the /admin/ virtual directory, then call a URL in the root that moves files from /admin/ back to the root, but that is entirely ghetto. I hope this post makes sense. Anyone else experience anything like this? The bottom line is that it seems virtual directories ONLY have access to themselves, and not their parent directories, no matter what credentials are used. Thanks!

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• Submit WordPress form programmatically

  - by songdogtech

  How can I let a user access a WordPress protected page with a URL that will submit the password in the form below? I want to be able to let a user get to a password protected WordPress page without needing to type the password, so when they go to the page, the password is submitted by a POST URL on page load. This not intended to be secure in any respect; I'll need to hardcode the password in the URL and the PHP. It's just for simplicity for the user, and once they're in, the cookie will let them in for 10 more days. I will select the particular user with separate PHP function that determines their IP or WordPress login status. I used Wireshark to find the POST string: post_password=mypassword&Submit=Submit but using this URL mydomain.com/wp-pass.php?post_password=mypassword&Submit=Submit gives me a blank page. This is the form: <form action="http://mydomain.com/wp-pass.php" method="post"> Password: <input name="post_password" type="password" size="20" /> <input type="submit" name="Submit" value="Submit" /></form> This is wp-pass.php: <?php require( dirname(__FILE__) . '/wp-load.php'); if ( get_magic_quotes_gpc() ) $_POST['post_password'] = stripslashes($_POST['post_password']); setcookie('wp-postpass_' . COOKIEHASH, $_POST['post_password'], time() + 864000, COOKIEPATH); wp_safe_redirect(wp_get_referer()); ?> What am I doing wrong? Or is there a better way to let a user into a password protected page automatically?

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• How can I do batch image processing with ImageJ in clojure?

  - by Robert McIntyre

  I want to use ImageJ to do some processing of several thousand images. Is there a way to take any general imageJ plugin and apply it to hundreds of images automatically? For example, say I want to take my thousand images and apply a polar transformation to each--- A polar transformation plugin for ImageJ can be found here: http://rsbweb.nih.gov/ij/plugins/polar-transformer.html Great! Let's use it. From: [http://albert.rierol.net/imagej_programming_tutorials.html#How%20to%20automate%20an%20ImageJ%20dialog] I find that I can apply a plugin using the following: (defn x-polar [imageP] (let [thread (Thread/currentThread) options ""] (.setName thread "Run$_polar-transform") (Macro/setOptions thread options) (IJ/runPlugIn imageP "Polar_Transformer" ""))) This is good because it suppresses the dialog which would otherwise pop up for every image. But running this always brings up a window containing the transformed image, when what I want is to simply return the transformed image. The stupidest way to do what I want is to just close the window that comes up and return the image which it was displaying. Does what I want but is absolutely retarded: (defn x-polar [imageP] (let [thread (Thread/currentThread) options ""] (.setName thread "Run$_polar-transform") (Macro/setOptions thread options) (IJ/runPlugIn imageP "Polar_Transformer" "") (let [return-image (IJ/getImage)] (.hide return-image) return-image))) I'm obviously missing something about how to use imageJ plugins in a programming context. Does anyone know the right way to do this? Thanks, --Robert McIntyre

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• How to compile ocaml to native code

  - by Indra Ginanjar

  i'm really interested learning ocaml, it fast (they said it could be compiled to native code) and it's functional. So i tried to code something easy like enabling mysql event scheduler. #load "unix.cma";; #directory "+mysql";; #load "mysql.cma";; let db = Mysql.quick_connect ~user:"username" ~password:"userpassword" ~database:"databasename"();; let sql = Printf.sprintf "SET GLOBAL EVENT_SCHEDULER=1;" in (Mysql.exec db sql);; It work fine on ocaml interpreter, but when i was trying to compile it to native (i'm using ubuntu karmic), neither of these command worked ocamlopt -o mysqleventon mysqleventon.ml unix.cmxa mysql.cmxa ocamlopt -o mysqleventon mysqleventon.ml unix.cma mysql.cma i also tried ocamlc -c mysqleventon.ml unix.cma mysql.cma all of them resulting same message File "mysqleventon.ml", line 1, characters 0-1: Error: Syntax error Then i tried to remove the "# load", so the code goes like this let db = Mysql.quick_connect ~user:"username" ~password:"userpassword" ~database:"databasename"();; let sql = Printf.sprintf "SET GLOBAL EVENT_SCHEDULER=1;" in (Mysql.exec db sql);; The ocamlopt resulting message File "mysqleventon.ml", line 1, characters 9-28: Error: Unbound value Mysql.quick_connect I hope someone could tell me, where did i'm doing wrong.

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• How to bind "rest" variables to list of values in macro in Scheme

  - by Slartibartfast

  I want to make a helper macro for writing match-extensions. I have something like this: (define-match-expander my-expander (? (stx) (let* ([dat (cdr (syntax-e stx))] [var1 (car dat))] [var2 (cadr dat)]) ;transformer goes here ))) So I wanted a macro that will do this let binding. I've started with something like this: (define-syntax-rule (define-my-expander (id vars ...) body) (define-match-expander id (? (stx) (match-let ([(vars ...) (cdr (syntax-e stx))]) body)))) but match-let isn't defined in transformation time. First question would be is there any other way of doing this (making this expanders, I mean)? Maybe there is already something similar in plt-scheme that I'm not aware of, or I'm doing it wrong in some way. Regardless of answer on the first question, if I ever want to bound list of variables to list of values inside of a macro, how should I do it? EDIT: In combination with Eli's answer macro now looks like this: (define-syntax-rule (define-my-expander (id vars ...) body) (define-match-expander id (? (stx) (syntax-case stx () [(_ vars ...) body]))))

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• How to set UCS2 in numpy?

  - by mindcorrosive

  I'm trying to build numpy 1.2.1 as a module for a third-party python interpreter (custom-built, py2.4 linux x86_64) so that I can make calls to numpy from within it. Let's call this one interpreter A. The thing is, the system-wide python interpreter (also py2.4, let's call it B) from the vendor is built with --enable-unicode=ucs4, while the custom one is with UCS2. Needless to say, when I try to build a module with B, I get an error when I try to import numpy in A -- it complains about undefined symbol _PyUnicodeUCS4_IsWhiteSpace. I've searched around and apparently there's no way around this but to compile a custom Python interpreter -- which I did (let's call it interpreter C), properly specifying the unicode string length (verifiable through sys.maxunicode). I managed to build numpy with C as well, surprisingly enough, but still the problem persists when I try to import it in interpreter C. Previously, when I built numpy using B, there were no problems when importing it in B, but A would complain. Perhaps there's an option when building numpy to specify the length of Unicode strings to be used, as when configuring Python builds? Or am I doing something else wrong? A few notes: Upgrading to newer versions of python and/or numpy is not an option - interpreter A will stay on this version of the grammar for the foreseeable future. Also, it is not possible to start the interpreter A in standalone mode to build numpy with it, as it needs some other libraries preloaded I know that this whole thing is a mess, but I'd appreciate any help I can get to make this work. If you need more information, please let me know, I'd be happy to oblige. Thanks to everybody for their time in advance.

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• Help me to refactor this F# code to tail recursion

  - by Kev

  I write some code to learning F#. Here is a example: let nextPrime list= let rec loop n= match n with | _ when (list |> List.filter (fun x -> x <= ( n |> double |> sqrt |> int)) |> List.forall (fun x -> n % x <> 0)) -> n | _ -> loop (n+1) loop (List.max list + 1) let rec findPrimes num= match num with | 1 -> [2] | n -> let temp = findPrimes <| n-1 (nextPrime temp ) :: temp //find 10 primes findPrimes 10 |> printfn "%A" I'm very happy that it just works! I'm totally beginner to recursion Recursion is a wonderful thing. I think findPrimes is not efficient. Someone help me to refactor findPrimes to tail recursion if possible? BTW, is there some more efficient way to find first n primes?

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• Syntax error beyond end of program

  - by a_m0d

  I am experimenting with writing a toy compiler in ocaml. Currently, I am trying to implement the offside rule for my lexer. However, I am having some trouble with the ocaml syntax (the compiler errors are extremely un-informative). The code below (33 lines of it) causes an error on line 34, beyond the end of the source code. I am unsure what is causing this error. open Printf let s = (Stack.create():int Stack.t); let rec check x = ( if Stack.is_empty s then Stack.push x s else if Stack.top s < x then ( Stack.push x s; printf "INDENT\n"; ) else if Stack.top s > x then ( printf "DEDENT\n"; Stack.pop s; check x; ) else printf "MATCHED\n"; ); let main () = ( check 0; check 4; check 6; check 8; check 5; ); let _ = Printexc.print main () Ocaml output: File "lexer.ml", line 34, characters 0-0: Error: Syntax error Can someone help me work out what the error is caused by and help me on my way to fixing it?

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