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• Which isolation level should I use for the following insert-if-not-present transaction?

  - by Steve Guidi

  I've written a linq-to-sql program that essentially performs an ETL task, and I've noticed many places where parallelization will improve its performance. However, I'm concerned about preventing uniquness constraint violations when two threads perform the following task (psuedo code). Record CreateRecord(string recordText) { using (MyDataContext database = GetDatabase()) { Record existingRecord = database.MyTable.FirstOrDefault(record.KeyPredicate()); if(existingRecord == null) { existingRecord = CreateRecord(recordText); database.MyTable.InsertOnSubmit(existingRecord); } database.SubmitChanges(); return existingRecord; } } In general, this code executes a SELECT statement to test for record existance, followed by an INSERT statement if the record doesn't exist. It is encapsulated by an implicit transaction. When two threads run this code for the same instance of recordText, I want to prevent them from simultaneously determining that the record doesn't exist, thereby both attempting to create the same record. An isolation level and explicit transaction will work well, except I'm not certain which isolation level I should use -- Serializable should work, but seems too strict. Is there a better choice?

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• Is the C++ compiler optimizer allowed to break my destructor ability to be called multiple times?

  - by sharptooth

  We once had an interview with a very experienced C++ developer who couldn't answer the following question: is it necessary to call the base class destructor from the derived class destructor in C++? Obviously the answer is no, C++ will call the base class destructor automagically anyway. But what if we attempt to do the call? As I see it the result will depend on whether the base class destructor can be called twice without invoking erroneous behavior. For example in this case: class BaseSafe { public: ~BaseSafe() { } private: int data; }; class DerivedSafe { public: ~DerivedSafe() { BaseSafe::~BaseSafe(); } }; everything will be fine - the BaseSafe destructor can be called twice safely and the program will run allright. But in this case: class BaseUnsafe { public: BaseUnsafe() { buffer = new char[100]; } ~BaseUnsafe () { delete[] buffer; } private: char* buffer; }; class DerivedUnsafe { public: ~DerivedUnsafe () { BaseUnsafe::~BaseUnsafe(); } }; the explicic call will run fine, but then the implicit (automagic) call to the destructor will trigger double-delete and undefined behavior. Looks like it is easy to avoid the UB in the second case. Just set buffer to null pointer after delete[]. But will this help? I mean the destructor is expected to only be run once on a fully constructed object, so the optimizer could decide that setting buffer to null pointer makes no sense and eliminate that code exposing the program to double-delete. Is the compiler allowed to do that?

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• interface variables are final and static by default and methods are public and abstract

  - by sap

  The question is why it's been decided to have variable as final and static and methods as public and abstract by default. Is there any particular reason for making them implicit,variable as final and static and methods as public and abstract. Why they are not allowing static method but allowing static variable? We have interface to have feature of multiple inheritance in Java and to avoid diamond problem. But how it solves diamond problem,since it does not allow static methods. In the following program, both interfaces have method with the same name..but while implementing only one we implement...is this how diamond problem is solved? interface testInt{ int m = 0; void testMethod(); } interface testInt1{ int m = 10; void testMethod(); } public class interfaceCheck implements testInt, testInt1{ public void testMethod(){ System . out . println ( "m is"+ testInt.m ); System . out . println ( "Hi World!" ); } }

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• How to define default values optional fields in play framework forms?

  - by natalinobusa

  I am implementing a web api using the scala 2.0.2 play framework. I would like to extract and validate a number of get parameters. And for this I am using a play "form" which allows me to define optional fields. Problem: For those optional fields, I need to define a default value if the parameter is not passed. The code is intended to parse correctly these three use cases: /test?top=abc (error, abc is not an integer) /test?top=123 (valid, top is 123) /test (valid, top is 42 (default value)) I have come up with the following code: def test = Action { implicit request => case class CData(top:Int) val p = Form( mapping( "top" -> optional(number) )((top) => CData($top.getOrElse(42))) ((cdata:CData) => Some(Some(cdata.top))) ).bindFromRequest() Ok("all done.") } The code works, but it's definitely not elegant. There is a lot of boiler plate going on just to set up a default value for a missing request parameter. Can anyone suggest a cleaner and more coincise solution?

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• How to call a generic method with an anonymous type involving generics?

  - by Alex Black

  I've got this code that works: def testTypeSpecialization = { class Foo[T] def add[T](obj: Foo[T]): Foo[T] = obj def addInt[X <% Foo[Int]](obj: X): X = { add(obj) obj } val foo = addInt(new Foo[Int] { def someMethod: String = "Hello world" }) assert(true) } But, I'd like to write it like this: def testTypeSpecialization = { class Foo[T] def add[X, T <% Foo[X](obj: T): T = obj val foo = add(new Foo[Int] { def someMethod: String = "Hello world" }) assert(true) } This second one fails to compile: no implicit argument matching parameter type (Foo[Int]{ ... }) = Foo[Nothing] was found. Basically: I'd like to create a new anonymous class/instance on the fly (e.g. new Foo[Int] { ... } ), and pass it into an "add" method which will add it to a list, and then return it The key thing here is that the variable from "val foo = " I'd like its type to be the anonymous class, not Foo[Int], since it adds methods (someMethod in this example) Any ideas? I think the 2nd one fails because the type Int is being erased. I can apparently 'hint' the compiler like this: def testTypeSpecialization = { class Foo[T] def add[X, T <% Foo[X]](dummy: X, obj: T): T = obj val foo = add(2, new Foo[Int] { def someMethod: String = "Hello world" }) assert(true) }

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• How to take a collection of bytes and pull typed values out of it?

  - by Pat

  Say I have a collection of bytes var bytes = new byte[] {0, 1, 2, 3, 4, 5, 6, 7}; and I want to pull out a defined value from the bytes as a managed type, e.g. a ushort. What is a simple way to define what types reside at what location in the collection and pull out those values? One (ugly) way is to use System.BitConverter and a Queue or byte[] with an index and simply iterate through, e.g.: int index = 0; ushort first = System.BitConverter.ToUint16(bytes, index); index += 2; // size of a ushort int second = System.BitConverter.ToInt32(bytes, index); index += 4; ... This method gets very, very tedious when you deal with a lot of these structures! I know that there is the System.Runtime.InteropServices.StructLayoutAttribute which allows me to define the locations of types inside a struct or class, but there doesn't seem to be a way to import the collection of bytes into that struct. If I could somehow overlay the struct on the collection of bytes and pull out the values, that would be ideal. E.g. Foo foo = (Foo)bytes; // doesn't work because I'd need to implement the implicit operator ushort first = foo.first; int second = foo.second; ... [StructLayout(LayoutKind.Explicit, Size=FOO_SIZE)] public struct Foo { [FieldOffset(0)] public ushort first; [FieldOffset(2)] public int second; } Any thoughts on how to achieve this?

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• Guru of the Week 2 no match for the operator==

  - by Adam

  From Guru of the Week 2. We have the function: string FindAddr(const list<Employee> l, string name) { for( list<Employee>::const_iterator i = l.begin(); i != l.end(); i++) { if( *i == name ) // here will be compilation error { return (*i).addr; } } return ""; } I added dummy Employee class to that: class Employee { string n; public: string addr; Employee(string name) : n(name) {} Employee() {} string name() const { return n; } operator string() { return n; } }; And got compilation error: error: no match for ‘operator==’ in ‘i.std::_List_iterator<_Tp>::operator* [with _Tp = Employee]() == name’ It works only if add operator== to Employee. But, Herb Sutter wrote that: The Employee class isn't shown, but for this to work it must either have a conversion to string or a conversion ctor taking a string. But Employee has a conversion function and conversion constructor as well. GCC version 4.4.3. Compiled normally, g++ file.cpp without any flags. There should be implicit conversion and it should work, why it doesn't?

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• When to use reinterpret_cast?

  - by HeretoLearn

  I am little confused with the applicability of reinterpret_cast vs static_cast. From what I have read the general rules are to use static cast when the types can be interpreted at compile time hence the word static. This is the cast the C++ compiler uses internally for implicit casts also. reinterpret_cast are applicable in two scenarios, convert integer types to pointer types and vice versa or to convert one pointer type to another. The general idea I get is this is unportable and should be avoided. Where I am a little confused is one usage which I need, I am calling C++ from C and the C code needs to hold on to the C++ object so basically it holds a void*. What cast should be used to convert between the void * and the Class type? I have seen usage of both static_cast and reinterpret_cast? Though from what I have been reading it appears static is better as the cast can happen at compile time? Though it says to use reinterpret_cast to convert from one pointer type to another?

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• Create and define Vector

  - by zdmytriv

  I'm looking for method to create Vector and push some values without defining variable Vector. For example: I have function: public function bla(data:Vector.<Object>):void { ... } this function expects Vector as parameter. I can pass parameters this way var newVector:Vector.<Object> = new Vector.<Object>(); newVector.push("bla1"); newVector.push("bla2"); bla(newVector); Can I do it in one line in Flex? I'm looking for something like: bla(new Vector.<Object>().push("bla1").push("bla2")); I've also tried this: bla(function():Vector.<Object> { var result:Vector.<Object> = new Vector.<Object>(2, true); result.push("bla1"); result.push("bla2"); return result; }); But it complains: 1067: Implicit coercion of a value of type Function to an unrelated type __AS3__.vec:Vector.<Object>... Thanks

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• How can one make a 'passthru' function in C++ using macros or metaprogramming?

  - by Ryan

  So I have a series of global functions, say: foo_f1(int a, int b, char *c); foo_f2(int a); foo_f3(char *a); I want to make a C++ wrapper around these, something like: MyFoo::f1(int a, int b, char* c); MyFoo::f2(int a); MyFoo::f3(char* a); There's about 40 functions like this, 35 of them I just want to pass through to the global function, the other 5 I want to do something different with. Ideally the implementation of MyFoo.cpp would be something like: PASSTHRU( f1, (int a, int b, char *c) ); PASSTHRU( f2, (int a) ); MyFoo::f3(char *a) { //do my own thing here } But I'm having trouble figuring out an elegant way to make the above PASSTHRU macro. What I really need is something like the mythical X getArgs() below: MyFoo::f1(int a, int b, char *c) { X args = getArgs(); args++; //skip past implicit this.. ::f1(args); //pass args to global function } But short of dropping into assembly I can't find a good implementation of getArgs().

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• Oracle Insert via Select from multiple tables where one table may not have a row

  - by Mikezx6r

  I have a number of code value tables that contain a code and a description with a Long id. I now want to create an entry for an Account Type that references a number of codes, so I have something like this: insert into account_type_standard (account_type_Standard_id, tax_status_id, recipient_id) ( select account_type_standard_seq.nextval, ts.tax_status_id, r.recipient_id from tax_status ts, recipient r where ts.tax_status_code = ? and r.recipient_code = ?) This retrieves the appropriate values from the tax_status and recipient tables if a match is found for their respective codes. Unfortunately, recipient_code is nullable, and therefore the ? substitution value could be null. Of course, the implicit join doesn't return a row, so a row doesn't get inserted into my table. I've tried using NVL on the ? and on the r.recipient_id. I've tried to force an outer join on the r.recipient_code = ? by adding (+), but it's not an explicit join, so Oracle still didn't add another row. Anyone know of a way of doing this? I can obviously modify the statement so that I do the lookup of the recipient_id externally, and have a ? instead of r.recipient_id, and don't select from the recipient table at all, but I'd prefer to do all this in 1 SQL statement.

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• Reading input files in FORTRAN

  - by lollygagger

  Purpose: Create a program that takes two separate files, opens and reads them, assigns their contents to arrays, do some math with those arrays, create a new array with product numbers, print to a new file. Simple enough right? My input files have comment characters at the beginning. One trouble is, they are '#' which are comment characters for most plotting programs, but not FORTRAN. What is a simple way to tell the computer not to look at these characters? Since I have no previous FORTRAN experience, I am plowing through this with two test files. Here is what I have so far: PROGRAM gain IMPLICIT NONE REAL, DIMENSION (1:4, 1:8) :: X, Y, Z OPEN(1, FILE='test.out', & STATUS='OLD', ACTION='READ') ! opens the first file READ(1,*), X OPEN(2, FILE='test2.out', & STATUS='OLD', ACTION='READ') ! opens the second file READ(2,*), Y PRINT*, X, Y Z = X*Y ! PRINT*, Z OPEN(3, FILE='test3.out', STATUS='NEW', ACTION='WRITE') !creates a new file WRITE(3,*), Z CLOSE(1) CLOSE(2) CLOSE(3) END PROGRAM PS. Please do not overwhelm me with a bunch of code monkey gobblety gook. I am a total programming novice. I do not understand all the lingo, that is why I came here instead of searching for help in existing websites. Thanks.

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• GNU Makefile: multiple outputs from single rule + preventing intermediate files from being deleted

  - by makesaurus

  This is sort of a continuation of question from link text. The problem is that there is a rule generating multiple outputs from a single input, and the command is time-consuming so we would prefer to avoid recomputation. Now there is an additional twist, that we want to keep files from being deleted as intermediate files, and rules involve wildcards to allow for parameters. The solution suggested was that we set up the following rule: file-a.out: program file.in ./program file.in file-a.out file-b.out file-c.out file-b.out: file-a.out @ file-c.out: file-b.out @ Then, calling make file-c.out creates both and we avoid issues with running make in parallel with -j switch. All fine so far. The problem is the following. Because the above solution sets up a chain in the DAG, make considers it differently; the files file-a.out and file-b.out are treated as intermediate files, and they by default get deleted as unnecessary as soon as file-c.out is ready. A way of avoiding that was mentioned somewhere here, and consists of adding file-a.out and file-b.out as dependencies of a target .SECONDARY, which keeps them from being deleted. Unfortunately, this does not solve my case because my rules use wildcard patters; specifically, my rules look more like this: file-a-%.out: program file.in ./program $* file.in file-a-$*.out file-b-$*.out file-c-$*.out file-b-%.out: file-a-%.out @ file-c-%.out: file-b-%.out @ so that one can pass a parameter that gets included in the file name, for example by running make file-c-12.out The solution that make documentation suggests is to add these as implicit rules to the list of dependencies of .PRECIOUS, thus keeping these files from being deleted. The solution with .PRECIOUS works, but it also prevents these files from being deleted when a rule fails and files are incomplete. Is there any other way to make this work?

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• The HTTP verb POST used to access path '[my path]' is not allowed.

  - by Jed

  I am receiving an error that states: "The HTTP verb POST used to access path '[my path]' is not allowed.". The error is being caused by the fact that I am implementing an HTML form element that uses the POST method and does not explicitly define an .aspx page in its ACTION parameter. For example: <form action="" method="post"> <input type="submit" /> </form> The HTML above is on a file at "/foo/default.aspx". Now, if the user points the URL to the root directory "foo" without specifying the aspx file (i.e. "http://localhost/foo") and then submits the form, the error "The HTTP verb POST used to access path '/foo' is not allowed." will be thrown. However, if the user goes to "http://localhost/foo/default.aspx" and then submits the form, all goes well (even if the ACTION parameter is left empty). Note: If I explicitly add the name of the .aspx (default.aspx) page to the ACTION parameter, no errors are thrown. So the example below works fine regardless if the user defines the name of the file in the URL or not. <form action="default.aspx" method="post"> <input type="submit" /> </form> I was curious as to why the error was being thrown, so I read a Microsoft KB that states This problem occurs because a client makes an HTTP request by sending the POST method to a static HTML page. Static HTML pages do not support the POST method. I suppose the core of the explanation makes sense, however in my case, my form is not being sent to a static html page - it's being sent to the same page that the html form lives on (default.aspx)... this is implicit to an ACTION param that is left empty. Is it possible to configure IIS (or otherwise) that will allow us to do form POSTing and keep the ACTION param empty?

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• Writing a generic function that can take a Writer as well as an OutputStream

  - by ebruchez

  I wrote a couple of functions that look like this: def myWrite(os: OutputStream) = {} def myWrite(w: Writer) = {} Now both are very similar and I thought I would try to write a single parametrized version of the function. I started with a type with the two methods that are common in the Java OutputStream and Writer: type Writable[T] = { def close() : Unit def write(cbuf: Array[T], off: Int, len: Int): Unit } One issue is that OutputStream writes Byte and Writer writes Char, so I parametrized the type with T. Then I write my function: def myWrite[T, A[T] <: Writable[T]](out: A[T]) = {} and try to use it: val w = new java.io.StringWriter() myWrite(w) Result: <console>:9: error: type mismatch; found : java.io.StringWriter required: ?A[ ?T ] Note that implicit conversions are not applicable because they are ambiguous: both method any2ArrowAssoc in object Predef of type [A](x: A)ArrowAssoc[A] and method any2Ensuring in object Predef of type [A](x: A)Ensuring[A] are possible conversion functions from java.io.StringWriter to ?A[ ?T ] myWrite(w) I tried a few other combinations of types and parameters, to no avail so far. My question is whether there is a way of achieving this at all, and if so how. (Note that the implementation of myWrite will need, internally, to know the type T that parametrizes the write() method, because it needs to create a buffer as in new ArrayT.)

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• Operator overloading in generic struct: can I create overloads for specific kinds(?) of generic?

  - by Carson Myers

  I'm defining physical units in C#, using generic structs, and it was going okay until I got the error: One of the parameters of a binary operator must be the containing type when trying to overload the mathematical operators so that they convert between different units. So, I have something like this: public interface ScalarUnit { } public class Duration : ScalarUnit { } public struct Scalar<T> where T : ScalarUnit { public readonly double Value; public Scalar(double Value) { this.Value = Value; } public static implicit operator double(Scalar<T> Value) { return Value.Value; } } public interface VectorUnit { } public class Displacement : VectorUnit { } public class Velocity : VectorUnit { } public struct Vector<T> where T : VectorUnit { #... public static Vector<Velocity> operator /(Vector<Displacement> v1, Scalar<Duration> v2) { return new Vector<Velocity>(v1.Magnitude / v2, v1.Direction); } } There aren't any errors for the + and - operators, where I'm just working on a Vector<T>, but when I substitute a unit for T, suddenly it doesn't like it. Is there a way to make this work? I figured it would work, since Displacement implements the VectorUnit interface, and I have where T : VectorUnit in the struct header. Am I at least on the right track here? I'm new to C# so I have difficulty understanding what's going on sometimes.

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• Fortran severe (40) Error... Help?!

  - by Taka

  I can compile but when I run I get this error "forrtl: severe (40): recursive I/O operation, unit -1, file unknown" if I set n = 29 or more... Can anyone help with where I might have gone wrong? Thanks. PROGRAM SOLUTION IMPLICIT NONE ! Variable Declaration INTEGER :: i REAL :: dt DOUBLE PRECISION :: st(0:9) DOUBLE PRECISION :: stmean(0:9) DOUBLE PRECISION :: first_argument DOUBLE PRECISION :: second_argument DOUBLE PRECISION :: lci, uci, mean REAL :: exp1, n REAL :: r, segma ! Get inputs WRITE(*,*) 'Please enter number of trials: ' READ(*,*) n WRITE(*,*) dt=1.0 segma=0.2 r=0.1 ! For n Trials st(0)=35.0 stmean(0)=35.0 mean = stmean(0) PRINT *, 'For ', n ,' Trials' PRINT *,' 1 ',st(0) ! Calculate results DO i=0, n-2 first_argument = r-(1/2*(segma*segma))*dt exp1 = -(1/2)*(i*i) second_argument = segma*sqrt(dt)*((1/sqrt(2*3.1416))*exp(exp1)) st(i+1) = st(i) * exp(first_argument+second_argument) IF(st(i+1)<=20) THEN stmean(i+1) = 0.0 st(i+1) = st(i) else stmean(i+1) = st(i+1) ENDIF PRINT *,i+2,' ',stmean(i+1) mean = mean+stmean(i+1) END DO ! Output results uci = mean+(1.96*(segma/sqrt(n))) lci = mean-(1.96*(segma/sqrt(n))) PRINT *,'95% Confidence Interval for ', n, ' trials is between ', lci, ' and ', uci PRINT *,'' END PROGRAM SOLUTION

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• Can a member struct be zero-init from the constructor initializer list without calling memset?

  - by selbie

  Let's say I have the following structure declaration (simple struct with no constructor). struct Foo { int x; int y; int z; char szData[DATA_SIZE]; }; Now let's say this struct is a member of a C++ class as follows: class CFoobar { Foo _foo; public: CFoobar(); }; If I declare CFoobar's constructor as follows: CFoobar::CFoobar() { printf("_foo = {%d, %d, %d}\n", _foo.x, _foo.y,_foo.z); for (int x = 0; x < 100; x++) printf("%d\n", _foo.szData[x]); } As you would expect, when CFoobar's constructor runs, garbage data gets printed out Obviously, the easy fix is to memset or ZeroMemory &_foo. It's what I've always done... However, I did notice that if add _foo to the constructor's initialization list with no parameters as follows: CFoobar::CFoobar() : _foo() { That this appears to zero-out the member variables of _foo. At least that was the case with g++ on linux. Now here's my question: Is this standard C++, or is this compiler specific behavior? If it's standard behavior, can someone quote me a reference from an official source? Any "gotchas" in regards to implicit zero-init behavior with more complicated structs and classes?

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• Proc causing a random TypeError

  - by go____yourself

  I'm refactoring some code and this proc is causing an error randomly and I don't know why or how to debug it... Any ideas? New code with proc defense_moves, offense_moves = [], [] determine_move = ->move,side,i { side << move.count(move[i]) } defense.size.times { |i| determine_move.(defense, defense_moves, i) } offense.size.times { |i| determine_move.(offense, offense_moves, i) } dm = defense[defense_moves.index(defense_moves.max)].nil? ? [0] : defense[defense_moves.index(defense_moves.max)] om = offense[offense_moves.index(offense_moves.max)].nil? ? [0] : offense[offense_moves.index(offense_moves.max)] Original code: d = 0 defense_moves = [] loop do defense_moves << defense.count(defense[d]) break if defense.count(defense[d]).zero? d += 1 end o = 0 offense_moves = [] loop do offense_moves << offense.count(offense[o]) break if offense.count(offense[o]).zero? o += 1 end dm = defense[defense_moves.index(defense_moves.max)].nil? ? [0] : defense[defense_moves.index(defense_moves.max)] om = offense[offense_moves.index(offense_moves.max)].nil? ? [0] : offense[offense_moves.index(offense_moves.max)] TypeError ttt2.rb:95:in `[]': no implicit conversion from nil to integer (TypeError) from ttt2.rb:95:in `computer_make_move' from ttt2.rb:133:in `draw_board' from ttt2.rb:24:in `place' from ttt2.rb:209:in `block in start_new_game' from ttt2.rb:188:in `loop' from ttt2.rb:188:in `start_new_game' from ttt2.rb:199:in `block in start_new_game' from ttt2.rb:188:in `loop' from ttt2.rb:188:in `start_new_game' from ttt2.rb:199:in `block in start_new_game' from ttt2.rb:188:in `loop' from ttt2.rb:188:in `start_new_game' from ttt2.rb:199:in `block in start_new_game' from ttt2.rb:188:in `loop' from ttt2.rb:188:in `start_new_game' from ttt2.rb:199:in `block in start_new_game' from ttt2.rb:188:in `loop' from ttt2.rb:188:in `start_new_game' from ttt2.rb:234:in `<main>'

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• Why aren't Java's generics implicitly polymorphic?

  - by froadie

  I'm a bit confused about how Java generics handle inheritance / polymorphism. Assume the following hierarchy - Animal (Parent) Dog - Cat (Children) So suppose I have a method doSomething(List<Animal> animals). By all the rules of inheritance and polymorphism, I would assume that a List<Dog> is a List<Animal> and a List<Cat> is a List<Animal> - and so either one could be passed to this method. Not so. If I want to achieve this behavior, I have to explicitly tell the method to accept a list of any subset of Animal by saying doSomething(List<? extends Animal> animals). I understand that this is Java's behavior. My question is why? Why is polymorphism generally implicit, but when it comes to generics it must be specified?

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• Random Loss of precision in Python ReadLine()

  - by jackyouldon

  Hi all, We have a process which takes a very large csv (1.6GB) and breaks it down into pieces (in this case 3). This runs nightly and normally doesn't give us any problems. When it ran last night, however, the first of the output files had lost precision on the numeric fields in the data. The active ingredient in the script are the lines: while lineCounter <= chunk: oOutFile.write(oInFile.readline()) lineCounter = lineCounter + 1 and the normal output might be something like StringField1; StringField2; StringField3; StringField4; 1000000; StringField5; 0.000054454 etc. On this one occasion and in this one output file the numeric fields were all output with 6 zeros at the end i.e. StringField1; StringField2; StringField3; StringField4; 1000000.000000; StringField5; 0.000000 We are using Python v2.6 (and don't want to upgrade unless we really have to) but we can't afford to lose this data. Does anyone have any idea why this might have happened? If the readline is doing some kind of implicit conversion is there a way to do a binary read, because we really just want this data to pass through untouched? It is very wierd to us that this only affected one of the output files generated by the same script, and when it was rerun the output was as expected. thanks Jack

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• I just don't get the C++ Pointer/Reference system.

  - by gnm

  I've never had problems with references as in Python (implicit) or PHP (explicit &). In PHP you write $p = &$myvar; and you have $p as a reference pointing to $myVar. So I know in C++ you can do this: void setToSomething( int& var ) { var = 123; } int myInt; setToSomething( myInt ); Myint is now 123, why? Doesn't & mean "memory address of" x in C++? What do I do then if var is only the adress to myInt and not a pointer? void setToSomething( int* var ) { var* = 123; } int myInt; int* myIntPtr = &myInt; setToSomething( myIntPtr ); Does the above work as expected? I don't understand the difference between * and & in C++ fully. They tell you & is used to get the adress of a variable, but why IN GODS NAME does that help you in functions etc. like in the first example?

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• More SQL Smells

  - by Nick Harrison

  Let's continue exploring some of the SQL Smells from Phil's list. He has been putting together. Datatype mis-matches in predicates that rely on implicit conversion.(Plamen Ratchev) This is a great example poking holes in the whole theory of "If it works it's not broken" Queries will this probably will generally work and give the correct response. In fact, without careful analysis, you probably may be completely oblivious that there is even a problem. This subtle little problem will needlessly complicate queries and slow them down regardless of the indexes applied. Consider this example: CREATE TABLE [dbo].[Page](     [PageId] [int] IDENTITY(1,1) NOT NULL,     [Title] [varchar](75) NOT NULL,     [Sequence] [int] NOT NULL,     [ThemeId] [int] NOT NULL,     [CustomCss] [text] NOT NULL,     [CustomScript] [text] NOT NULL,     [PageGroupId] [int] NOT NULL;  CREATE PROCEDURE PageSelectBySequence ( @sequenceMin smallint , @sequenceMax smallint ) AS BEGIN SELECT [PageId] , [Title] , [Sequence] , [ThemeId] , [CustomCss] , [CustomScript] , [PageGroupId] FROM [CMS].[dbo].[Page] WHERE Sequence BETWEEN @sequenceMin AND @SequenceMax END  Note that the Sequence column is defined as int while the sequence parameter is defined as a small int. The problem is that the database may have to do a lot of type conversions to evaluate the query. In some cases, this may even negate the indexes that you have in place. Using Correlated subqueries instead of a join   (Dave_Levy/ Plamen Ratchev) There are two main problems here. The first is a little subjective, since this is a non-standard way of expressing the query, it is harder to understand. The other problem is much more objective and potentially problematic. You are taking much of the control away from the optimizer. Written properly, such a query may well out perform a corresponding query written with traditional joins. More likely than not, performance will degrade. Whenever you assume that you know better than the optimizer, you will most likely be wrong. This is the fundmental problem with any hint. Consider a query like this:  SELECT Page.Title , Page.Sequence , Page.ThemeId , Page.CustomCss , Page.CustomScript , PageEffectParams.Name , PageEffectParams.Value , ( SELECT EffectName FROM dbo.Effect WHERE EffectId = dbo.PageEffects.EffectId ) AS EffectName FROM Page INNER JOIN PageEffect ON Page.PageId = PageEffects.PageId INNER JOIN PageEffectParam ON PageEffects.PageEffectId = PageEffectParams.PageEffectId  This can and should be written as:  SELECT Page.Title , Page.Sequence , Page.ThemeId , Page.CustomCss , Page.CustomScript , PageEffectParams.Name , PageEffectParams.Value , EffectName FROM Page INNER JOIN PageEffect ON Page.PageId = PageEffects.PageId INNER JOIN PageEffectParam ON PageEffects.PageEffectId = PageEffectParams.PageEffectId INNER JOIN dbo.Effect ON dbo.Effects.EffectId = dbo.PageEffects.EffectId  The correlated query may just as easily show up in the where clause. It's not a good idea in the select clause or the where clause. Few or No comments. This one is a bit more complicated and controversial. All comments are not created equal. Some comments are helpful and need to be included. Other comments are not necessary and may indicate a problem. I tend to follow the rule of thumb that comments that explain why are good. Comments that explain how are bad. Many people may be shocked to hear the idea of a bad comment, but hear me out. If a comment is needed to explain what is going on or how it works, the logic is too complex and needs to be simplified. Comments that explain why are good. Comments may explain why the sql is needed are good. Comments that explain where the sql is used are good. Comments that explain how tables are related should not be needed if the sql is well written. If they are needed, you need to consider reworking the sql or simplify your data model. Use of functions in a WHERE clause. (Anil Das) Calling a function in the where clause will often negate the indexing strategy. The function will be called for every record considered. This will often a force a full table scan on the tables affected. Calling a function will not guarantee that there is a full table scan, but there is a good chance that it will. If you find that you often need to write queries using a particular function, you may need to add a column to the table that has the function already applied.

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• WEB203 &ndash; Jump into Silverlight!&hellip; and Become Effective Immediately with Tim Huckaby, Fou

  - by Robert Burger

  Getting ready for the good stuff. Definitely wish there were more Silverlight and WCF RIA sessions, but this is a start.  Was lucky to get a coveted power-enabled seat.  Luckily, due to my trustily slow Verizon data card, I can get these notes out amidst a total Internet outage here.  This is the second breakout session of the day, and is by far standing-room only.  I stepped out before the session started to get a cool Diet COKE and wouldn’t have gotten back in if I didn’t already have a seat. Tim says this is an intro session and that he’s been begging for intro sessions at TechEd for years and that by looking at this audience, he thinks the demand is there.  Admittedly, I didn’t know this was an intro session, or I might have gone elsewhere.  But, it was the very first Silverlight session, so I had to be here. Tim says he will be providing a very good comprehensive reference application at the end of the presentation.  He has just demoed it, and it is a full CRUD-based Sales Manager application based on…  AdventureWorks! Session Agenda What it is / How to get started Declarative Programming Layout and Controls, Events and Commands Working with Data Adding Style to Your Application   Silverlight…  “WPF Light” Why is the download 4.2MB?  Because the direct competitor is a 4.2MB download.  There is no technical reason it is not the entire framework.  It is purely to “be competitive”.   Getting Started Get all of the following downloads from www.silverlight.net/getstarted Install VS2010 or Visual Web Developer Express 2010 Install Silverlight 4 Tools for VS2010 Install Expression Blend 4 Install the Silverlight 4 Toolkit   Reference Application Features Uses MVVM pattern – a way to move data access code that would normally be inline within the UI and placing it in nice data access libraries Images loaded dynamically from the database, converting GIF to PNG because Silverlight does not support GIF. LINQ to SQL is the data access model WCF is the data provider and is using binary message encoding   Declarative Programming XAML replaces code for UI representation Attributes control Layout and Style Event handlers wired-up in XAML Declarative Data Binding   Layout Overview Content rendering flows inside of parent Fixed positioning (Canvas) is seldom used Panels are used to house content Margins and Padding over fixed size   Panels StackPanel – Arranges child elements into a single line oriented horizontally or vertically Grid – A flexible grid are that consists of rows and columns Canvas – An are where positions are specifically fixed WrapPanel (in Toolkit) – Positions child elements in sequential position left to right and top to bottom. DockPanel (in Toolkit) – Positions child controls within a dockable area   Positioning Horizontal and Vertical Alignment Margin – Separates an element from neighboring elements Padding – Enlarges the effective size of an element by a thickness   Controls Overview Not all controls created equal Silverlight, as a subset of WPF, so many WPF controls do not exist in the core Siverlight release Silverlight Toolkit continues to add controls, but are released in different quality bands Plenty of good 3rd party controls to fill the gaps Windows Phone 7 is to have 95% of controls available in Silverlight Core and Toolkit.   Events and Commands Standard .NET Events Routed Events Commands – based on the ICommand interface – logical action that can be invoked in several ways   Adding Style to Your Application Resource Dictionaries – Contains a hash table of key/value pairs.  Silverlight can only use Static Resources whereas WPF can also use Dynamic Resources Visual State Manager Silverlight 4 supports Implicit styles ResourceDictionary.MergedDictionaries combines many different file-based resources   Downloads

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• Silverlight Cream for February 13, 2011 -- #1046

  - by Dave Campbell

  In this Issue: Loek van den Ouweland, Colin Eberhardt, Rudi Grobler, Joost van Schaik, Mike Taulty(-2-, -3-), Deborah Kurata, David Kelley, Peter Foot, Samuel Jack(-2-), and WindowsPhoneGeek(-2-). Above the Fold: Silverlight: "Silverlight Simple MVVM Commanding" Deborah Kurata WP7: "WP7 CustomInputPrompt control with Cancel button" WindowsPhoneGeek Expression Blend: "Silverlight Templated Image Button with two images" Loek van den Ouweland Shoutouts: Dave Campbell posted a write-up about the project he's on and the use of Sterling: Sterling Object-Oriented Database for ISO 1.0 Released!... Also see Jeremy Likness' post on the 1.0 release: Sterling Object-Oriented Database 1.0 RTM Not necessarily Silverlight, but darn cool, a great control by Sasha Barber: WPF : A Weird 3d based control snoutholder announced new content: Windows Phone 7 QuickStarts Live! From SilverlightCream.com: Silverlight Templated Image Button with two images Loek van den Ouweland has a video tutorial up for creating an ImageButton with a hover state... Expression Blend coolness, and check out the external links he has to their training site. Windows Phone 7 Performance Measurements – Emulator vs. Hardware Colin Eberhardt's latest is a popular post comparing performance metrics between the WP7 emulator and a real device. Mileage may vary, but I'm pretty sure the overall results are conculsive, and should help the way you view your app as you're building in the emulator. WP7: WebClient vs HttpWebRequest Rudi Grobler's latest is a discussion of WebClient and HttpWebRequest, gives coding examples of each plus discussion of why you may choose one over the other... and pay attention to his comment about mobile providers. A Blendable Windows Phone 7 / Silverlight clipping behavior Joost van Schaik posted this WP7/Silverlight clipping behavior he developed because all the other solutions were not blendable. Another really useful piece of code from Joost! Blend Bits 22–Being Stylish Mike Taulty has 3 more episodes in his Blend Bits series... first up is on one Styles... explicit, implicit, inheriting... you name it, he's covering it! Blend Bits 23–Templating Part 1 MIke Taulty then has the beginning of a series within his Blend Bits series on Templating. This is something you just have to either bite the bullet and go with Blend to do, or consume someone else's work. Mike shows us how to do it ourself by tweaking the visual aspects of a checkbox Blend Bits 24–Templating Part 2 In part 2 of the Templating series, Mike Taulty digs deeper into Blend and cracks open the Listbox control to take a bunch of the inner elements out for a spin... fun stuff and great tutorial, Mike! Silverlight Simple MVVM Commanding Deborah Kurata has another great MVVM post up... if you don't have your head wrapped around commanding yet, this is a good place to start that process... VB and C# as always. App Development for Windows Phone 7 101 David Kelley goes through the basics of producing a WP7 app both from the Silverlight and XNA side... good info and good external links to get you going. Copyable TextBlock for Windows Phone Peter Foot takes a look at the Copy/Paste functionality in WP7 and how to apply it to a TextBlock... which is NOT an out-of-the-box solution. How to deploy to, and debug, multiple instances of the Windows Phone 7 emulator Samuel Jack has a couple posts up this week... first is this clever one on running multiple copies of the emulator at once... too cool for debugging a multi-player game! Multi-player enabling my Windows Phone 7 game: Day 3 – The Server Side Samuel Jack's latest is a detailed look at his day 3 adventure of taking his multi-player game to WP7... lots of information and external links... what do you say, give him another day? :) WP7 CustomInputPrompt control with Cancel button WindowsPhoneGeek has a couple more posts up... first is this "CustomInputPrompt" control based off the InputPrompt from Coding4Fun. Implementing Windows Phone 7 DataTemplateSelector and CustomDataTemplateSelector In his latest post, WindowsPhoneGeek writes a DataTemplateSelector to allow different data templates for different list elements based on the type of the element. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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