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• Multiple actions upon a case statement in Haskell

  - by Schroedinger

  One last question for the evening, I'm building the main input function of my Haskell program and I have to check for the args that are brought in so I use args <- getArgs case length args of 0 -> putStrLn "No Arguments, exiting" otherwise -> { other methods here} Is there an intelligent way of setting up other methods, or is it in my best interest to write a function that the other case is thrown to within the main? Or is there an even better solution to the issue of cases. I've just got to take in one name.

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• Fun with Lambdas

  - by Roman A. Taycher

  Not having them used them all that much I'm not quite sure all that lambdas/blocks can be used for (other than map/collect/do/lightweight local function syntax). If some people could post some interesting but somewhat understandable examples (with explanation). preferred languages for examples: python, smalltalk, haskell

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• SQL Server: collect values in an aggregation temporarily and reuse in the same query

  - by Erwin Brandstetter

  How do I accumulate values in t-SQL? AFAIK there is no ARRAY type. I want to reuse the values like demonstrated in this PostgreSQL example using array_agg(). SELECT a[1] || a[i] AS foo ,a[2] || a[5] AS bar -- assuming we have >= 5 rows for simplicity FROM ( SELECT array_agg(text_col ORDER BY text_col) AS a ,count(*)::int4 AS i FROM tbl WHERE id between 10 AND 100 ) x How would I best solve this with t-SQL? Best I could come up with are two CTE and subselects: ;WITH x AS ( SELECT row_number() OVER (ORDER BY name) AS rn ,name AS a FROM #t WHERE id between 10 AND 100 ), i AS ( SELECT count(*) AS i FROM x ) SELECT (SELECT a FROM x WHERE rn = 1) + (SELECT a FROM x WHERE rn = i) AS foo ,(SELECT a FROM x WHERE rn = 2) + (SELECT a FROM x WHERE rn = 5) AS bar FROM i Test setup: CREATE TABLE #t( id INT PRIMARY KEY ,name NVARCHAR(100)) INSERT INTO #t VALUES (3 , 'John') ,(5 , 'Mary') ,(8 , 'Michael') ,(13, 'Steve') ,(21, 'Jack') ,(34, 'Pete') ,(57, 'Ami') ,(88, 'Bob') Is there a simpler way?

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• Named arguments in Mathematica.

  - by dreeves

  What's the best/canonical way to define a function with optional named arguments? To make it concrete, let's create a function foo with named arguments a, b, and c, which default to 1, 2, and 3, respectively. For comparison, here's a version of foo with positional arguments: foo[a_:1, b_:2, c_:3] := bar[a,b,c] Here is sample input and output for the named-arguments version of foo: foo[] --> bar[1,2,3] foo[b->7] --> bar[1,7,3] foo[a->6, b->7, c->8] --> bar[6,7,8] It should of course also be easy to have positional arguments before the named arguments.

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• Is there a way in PHP to check if a directory is a symlink?

  - by tixrus

  The title says it all. I have symlinks to certain directories because the directories' names have non English characters that I got fed up trying to get apache's rewrite rules to match. There's a bounty on that question http://stackoverflow.com/questions/2916194/trouble-with-utf-8-chars-apache2-rewrite-rulesif anyone wants to go for it, and from the looks of things a lot of people would like to see a general solution to this problem, but meanwhile I made a plain ascii symlink to each of these offending directories. Now the rewrite rules are back to just alpha and _ and - and my security concerns are less and it loads the resources I want. But I still need the actual target directory name for display purposes. I googled "PHP directory info, PHP symlink" but didn't find anything. I need to do something like this: if (is_symlink($myResDirName)) { $realDirName = follow_symlink($myResDirName); }

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• How to explain method calls?

  - by forki23

  Hi, let's consider a small method: int MyFunction(string foo, int bar) { ... } and some calls: MyFunction("",0) int x = MyFunction(foo1,bar1) How would you explain this to a non-technical persons? Has anybody a nice metaphor? I tried to explain method calling (or function application) several times, but I failed. Seems I can't find the right words here. Regards, forki

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• Displaying a single rank in MySQL table

  - by MichaelInno

  I have a table called 'highscores' that looks like this. id udid name score 1 1111 Mike 200 2 3333 Joe 300 3 4444 Billy 50 4 0000 Loser 10 5 DDDD Face 400 Given a specific udid, I want to return the rank of that row by their score value. i.e. if udid given = 0000, I should return 5. Any idea how to write this query for a MySQL database?

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• What is lifetime of lambda-derived implicit functors in C++ ?

  - by Fyodor Soikin

  The question is simple: what is lifetime of that functor object that is automatically generated for me by the C++ compiler when I write a lambda-expression? I did a quick search, but couldn't find a satisfactory answer. In particular, if I pass the lambda somewhere, and it gets remembered there, and then I go out of scope, what's going to happen once my lambda is called later and tries to access my stack-allocated, but no longer alive, captured variables? Or does the compiler prevent such situation in some way? Or what?

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• Dealing with multiple Javascript IF statements.

  - by Joey

  Is it possible to put multiple IF statements in Javascript? If so, I'm having a fair amount of trouble with the statement below. I was wondering if you can put another IF statement in between if (data == 'valid') AND else? I want to add another if data =='concept') between the two. if (data == 'valid') { $("#file").slideUp(function () { $("#file").before('<div class="approvedMessage">WIN WIN WIN!</div>'); setTimeout(ApprovedProof, 5000); }); function ApprovedProof() { $("#file").slideDown(); $('.approvedMessage').fadeOut(); } } else { $("#file").slideUp(function () { $("#file").before('<div class="deniedMessage">NO NO NO!</div>'); setTimeout(DeniedProof, 5000); }); function DeniedProof() { $("#file").slideDown(); $('.deniedMessage').fadeOut(); } }

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• Help on understanding JS

  - by Anonymous

  I have thos piece of code: Math&&Math.random?Math.floor(Math.random()*10000000000000):Date.getTime(); And as far as i know && is logic operator for AND, so im trying to convert this into PHP and this is where i got: intval(floor(time()/10800000)%10+(rand()?floor(rand()*10000000000000):time())) The problem is that i can't understand the first part Math&& Can anyone help with this one cause i always get negative result, when i should get positive (probably the logic rand-time is not working in my php example)

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• Python: re-initialize a function's default value for subsequent calls to the function.

  - by Peter Stewart

  I have a function that calls itself to increment and decrement a stack. I need to call it a number of times, and I'd like it to work the same way in subsequent calls but, as expected, it doesn't re-use the default value. I've read that this is a newbie trap and I've seen suggested solutions, but I haven't been able to make any solution work. It would be nice to be able to "fun.reset" def a(x, stack = [None]): print x,' ', stack if x > 5: temp = stack.pop() if x <=5: stack.append(1) if stack == []: return a(x + 1) print a(0) print a(2) #second call print a(3) #third call I expected this to work, but it doesn't. print a(0, [None]) print a(2, [None]) #second call print a(3, [None]) #third call Can I reset the function to it's initial state? Any help would be appreciated.

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• What is a RECURSIVE Function in PHP?

  - by Imran

  Can anyone please explain a recursive function to me in PHP (without using Fibonacci) in layman language and using examples? i was looking at an example but the Fibonacci totally lost me! Thank you in advance ;-) Also how often do you use them in web development?

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• Testing for existence using SELECT WHERE HAVING and NOT HAVING in a grouped subset

  - by IanC

  I have data on which I need to count +1 if a particular condition exists or another condition doesn't exist. I'm using SQL Server 2008. I shred the following simplified sample XML into a temp table and validate it: <product type="1"> <param type="1"> <item mode="0" weight="1" /> </param> <param type="2"> <item mode="1" weight="1" /> <item mode="0" weight="0.1" /> </param> <param type="3"> <item mode="1" weight="0.75" /> <item mode="1" weight="0.25" /> </param> </product> The validation in concern is the following rule: For each product type, for each param type, mode may be 0 & (1 || 2). In other words, there may be a 0(s), but then 1s or 2s are required, or there may be only 1(s) or 2(s). There cannot be only 0s, and there cannot be 1s and 2s. The only part I haven't figured out is how to detect if there are only 0s. This seems like a "not having" problem. The validation code (for this part): WITH t1 AS ( SELECT SUM(t.ParamWeight) AS S, COUNT(1) AS C, t.ProductTypeID, t.ParamTypeID, t.Mode FROM @t AS t GROUP BY t.ProductTypeID, t.ParamTypeID, t.Mode ), ... UNION ALL SELECT TOP (1) 1 -- only mode 0 & (1 || 2) is allowed FROM t1 WHERE t1.Mode IN (1, 2) GROUP BY t1.ProductTypeID, t1.ParamTypeID HAVING COUNT(1) > 1 UNION ALL ... ) SELECT @C = COUNT(1) FROM t2 This will show if any mode 1s & 2s are mixed, but not if the group contains only a 0. I'm sure there is a simple solution, but it's evading me right now. EDIT: I thought of a "cheat" that works perfectly. I added the following to the above: SELECT TOP (1) 1 -- only mode 0 & (null || 1 || 2) is allowed FROM t1 GROUP BY t1.ProductTypeID, t1.ParamTypeID HAVING SUM(t1.Mode) = 0 However, I'd still like to know how to do this without cheating.

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• Compiler/Linking Error: Freedup

  - by nym

  I've been trying to compile a program for hardlinking duplicate files called freedup. I did try to email the author/maintainer of the program, but it's been a long time and I haven't heard anything back from him. I'm trying to compile the program from a cygwin environment using the latest stable versions of gcc (3.4.4-999) and make (3.81-2). I've tried deleting all the object files and running make, but I always get the following error: freedup.o: In function 'main': /home/[user]/freedup-1.5/freedup.c:1791: undefined reference to '_hashed' collect2: ld returned 1 exit status make: * * * [freedup] Error 1 I did take a look at the source code and saw that the "hashed" function is an inline function (which I didn't think had to be declared outside of the source file... but that's just what I gathered from some preliminary googling). If anyone would be kind enough to try compiling this program in a windows environment and has any luck, I'd really appreciate it. Thanks The direct link for the source files is: http://freedup.org/freedup-1.5-3-src.tgz

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• WPF: Can I use VisualStateManager to change alignment?

  - by kennethkryger

  Hi, I've got this "object-stack" - Window --- Grid (VerticalAlignment = Stretch) ----- Border (VerticalAlignment = Stretch OR Top) The Border a primitive UserControl right now to keep things simple for me. I'd like to be able to use the VisualStateManager to toggle the VerticalAlignment-property of the Border, so that the "Normal-state" equals VerticalAlignment.Top and "Expanded-state" equals VerticalAlignment.Stretch. Is this possible? Also, I'd like to use an easing function, when swithing between the two states.

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• python report generator from a pdf file

  - by joven

  I have a PDF copy of a file for creating a report. Based on this form, we will generate a report. Is there any way that I can fill out the needed fields on the PDF form using python? How?

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• Code equivalence between Javascript and PHP

  - by xdevel2000

  I'm trying to learn PHP and I wish to know if there are some function equivalence constructs: In JS I can do: var t = function() {}; t(); myObj.DoStuff = function() {} // here I add a method at run-time myObj.DoStuff(); myObj["DoStuff"](); var j = myObj.DoStuff; j(); and so other things with function evaluation. In Js objects are associative arrays so every properties is accessible with the subscript notation... Can I add a method at run-time to a class template so next its object instances can have it? In JS I can do that via a prototype function property.

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• C++ vs. C++/CLI: Const qualification of virtual function parameters

  - by James McNellis

  [All of the following was tested using Visual Studio 2008 SP1] In C++, const qualification of parameter types does not affect the type of a function (8.3.5/3: "Any cv-qualifier modifying a parameter type is deleted") So, for example, in the following class hierarchy, Derived::Foo overrides Base::Foo: struct Base { virtual void Foo(const int i) { } }; struct Derived : Base { virtual void Foo(int i) { } }; Consider a similar hierarchy in C++/CLI: ref class Base abstract { public: virtual void Foo(const int) = 0; }; ref class Derived : public Base { public: virtual void Foo(int i) override { } }; If I then create an instance of Derived: int main(array<System::String ^> ^args) { Derived^ d = gcnew Derived; } it compiles without errors or warnings. When I run it, it throws the following exception and then terminates: An unhandled exception of type 'System.TypeLoadException' occurred in ClrVirtualTest.exe Additional information: Method 'Foo' in type 'Derived'...does not have an implementation. That exception seems to indicate that the const qualification of the parameter does affect the type of the function in C++/CLI (or, at least it affects overriding in some way). However, if I comment out the line containing the definition of Derived::Foo, the compiler reports the following error (on the line in main where the instance of Derived is instantiated): error C2259: 'Derived': cannot instantiate abstract class If I add the const qualifier to the parameter of Derived::Foo or remove the const qualifier from the parameter of Base::Foo, it compiles and runs with no errors. I would think that if the const qualification of the parameter affects the type of the function, I should get this error if the const qualification of the parameter in the derived class virtual function does not match the const qualification of the parameter in the base class virtual function. If I change the type of Derived::Foo's parameter from an int to a double, I get the following warning (in addition to the aforementioned error, C2259): warning C4490: 'override': incorrect use of override specifier; 'Derived::Foo' does not match a base ref class method So, my question is, effectively, does the const qualification of function parameters affect the type of the function in C++/CLI? If so, why does this compile and why are there no errors or warnings? If not, why is an exception thrown?

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• Haskell FlatMap

  - by mvid

  I am a beginner interested in Haskell, and I have been trying to implement the flatmap (=) on my own to better understand it. Currently I have flatmap :: (t -> a) -> [t] -> [a] flatmap _ [] = [] flatmap f (x:xs) = f x : flatmap f xs which implements the "map" part but not the "flat". Most of the modifications I make result in the disheartening and fairly informationless Occurs check: cannot construct the infinite type: a = [a] When generalising the type(s) for `flatmap' error. What am I missing?

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• Is it possible to call a JavaScript function using an array of values as arguments ?

  - by Moshe Levine

  I'm looking for another way of doing the following: function call_any_function(func, parameters){ // func => any given function if(parameters.length==0){ func(); } if(parameters.length==1){ func(parameters[0]); } if(parameters.length==2){ func(parameters[0], parameters[1]); } if(parameters.length==3){ func(parameters[0], parameters[1], parameters[2]); } if(parameters.length==4){ func(parameters[0], parameters[1], parameters[2], parameters[3]); } // ... and so on }; It seems basic but I couldn't find an answer. Any ideas?

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• postgresql syntax while exists loop

  - by veilig

  I'm working at function from Joe Celkos book - Trees and Hierarchies in SQL for Smarties I'm trying to delete a subtree from an adjacency list but part my function is not working yet. WHILE EXISTS –– mark leaf nodes (SELECT * FROM OrgChart WHERE boss_emp_nbr = -99999 AND emp_nbr > -99999) LOOP –– get list of next level subordinates DELETE FROM WorkingTable; INSERT INTO WorkingTable SELECT emp_nbr FROM OrgChart WHERE boss_emp_nbr = -99999; –– mark next level of subordinates UPDATE OrgChart SET emp_nbr = -99999 WHERE boss_emp_nbr IN (SELECT emp_nbr FROM WorkingTable); END LOOP; my question: is the WHILE EXISTS correct for use w/ postgresql? I appear to be stumbling and getting caught in an infinite loop in this part. Perhaps there is a more correct syntax I am unaware of.

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• Get number of posts in a topic PHP

  - by Wayne

  How do I get to display the number of posts on a topic like a forum. I used this... (how very noobish): function numberofposts($n) { $sql = "SELECT * FROM posts WHERE topic_id = '" . $n . "'"; $result = mysql_query($sql) or die(mysql_error()); $count = mysql_num_rows($result); echo number_format($count); } The while loop of listing topics: <div class="topics"> <div class="topic-name"> <p><?php echo $row['topic_title']; ?></p> </div> <div class="topic-posts"> <p><?php echo numberofposts($row['topic_id']); ?></p> </div> </div> Although it is a bad method of doing this... All I need is to know what would be the best method, don't just point me out to a website, do it here, because I'm trying to learn much. Okay? :D Thanks.

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• PIG doesn't read my custom InputFormat

  - by Simon Guo

  I have a custom MyInputFormat that suppose to deal with record boundary problem for multi-lined inputs. But when I put the MyInputFormat into my UDF load function. As follow: public class EccUDFLogLoader extends LoadFunc { @Override public InputFormat getInputFormat() { System.out.println("I am in getInputFormat function"); return new MyInputFormat(); } } public class MyInputFormat extends TextInputFormat { public RecordReader createRecordReader(InputSplit inputSplit, JobConf jobConf) throws IOException { System.out.prinln("I am in createRecordReader"); //MyRecordReader suppose to handle record boundary return new MyRecordReader((FileSplit)inputSplit, jobConf); } } For each mapper, it print out I am in getInputFormat function but not I am in createRecordReader. I am wondering if anyone can provide a hint on how to hoop up my costome MyInputFormat to PIG's UDF loader? Much Thanks. I am using PIG on Amazon EMR.

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• JavaScript function, which reads connections between objects

  - by Nikita Sumeiko

  I have a JavaScript literal: var members = { "mother": { "name" : "Mary", "age" : "48", "connection": { "brother" : "sun" } }, "father": { "name" : "Bill", "age" : "50" }, "brother": { "name" : "Alex", "age" : "28" } } Than I have a function, which should read connections from the literal above. It looks like this: function findRelations(members){ var wires = new Array(); var count = 0; for (n = 0; n < members.length; n++){ alert(members.length); // this alert is undefined if (members[n].connection){ for (i = 0; i < members[n].connection[0].length; i++){ var mw = new Array(); var destination = 0; for (m = 0; m < members.length; m ++){ if (members[m] == members[n].connection[0]){ destination = m; mw = [n, destination]; wires [count] = mw; count++; } } } } } return wires; } However, when I run this function, I get nothing. And the first alert, which is placed inside the function shows 'undefined' at all. findRelations(members); alert("Found " + wires.length + " connections"); I guess that's because of JavaScript literal. Could you suggest how to change a function or perhaps to change litteral to JSON array to get it work?! And at the end to get 'm' and 'n' values as numbers.

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• Need for prefixing a function with (void)...

  - by puffadder

  Hi All, I recently came across a rather unusual coding convention wherein the call for a function returning "void" is prefixed with (void). e.g. (void) MyFunction(); Is it any different from the function call like: MyFunction(); Has it got any advantage or is it yet another needless but there coding convention of some sort?

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