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  • Is the F# language reference documentation available in an offline format (PDF, CHM)?

    - by stakx
    I've found several posts on hubFS of people asking if there is, or will be, offline documentation for F#. These posts haven't been answered. So I want to give it a shot and ask the same question here on SO. Where I've looked for offline documentation so far: The April 2010 CTP release of Visual F# (version 2.0) is available for VS 2008, but it doesn't come without an offline help. There's a question on SO about offline documentation for various programming languages, but F# isn't mentioned there at the time of this writing. There is of course Microsoft's F# language reference documentation (available on MSDN), which could be downloaded for offline browsing using e.g. wget. Question: Does anyone know whether any "official" offline documentation is on the way, anytime soon? (And related to this, albeit this probably can't be answered objectively: Would it be reasonable to expect that F# likely won't undergo ECMA or ISO standardization, ie. there likely won't be a standards document describing the language?)

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  • Ruby implementation of conversion between Latitude/Longitude and OS National Grid Reference point?

    - by Harry Wood
    For converting between Latitude/Longitude and UK's Ordnance Survey National Grid eastings and northings, this seems to be the most popular explanation and reference implementation in JavaScript: http://www.movable-type.co.uk/scripts/latlong-gridref.html The web is littered with other implementations in different languages. Making the conversion via PostGIS queries is another alternative. ...but did anyone implement this maths in ruby? OSGridToLatLong is the direction I'm looking for just at this moment, but I would have thought a library for converting in both directions must surely be available in a gem somewhere. I'm just not searching for the right thing.

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  • Why isn't my Ruby object deleted when the last reference goes out of scope?

    - by Andrew Clegg
    Hi gurus, I've found a weird effect when trying to track down a memory leak in a Rails app. Can anyone explain what's going on here? Save this script as a plain Ruby script (Rails not necessary): class Fnord def to_s 'fnord' end end def test f = Fnord.new end test GC.start sleep 2 ObjectSpace.each_object do |o| puts o if o.is_a? Fnord end When I run this via ruby 1.8.7 (2009-06-12 patchlevel 174) [i486-linux] I get the following: bash $ ruby var_test fnord Although the variable f is out of scope, there are no other references to the single Fnord object, and I've garbage collected, the object still seems to exist. Is this a nefarious memory leak of some sort, or am I completely missing something about Ruby? Further, if I change the test method to this: def test f = Fnord.new f = nil end I get no output. But surely this should not change the semantics here? Many thanks!

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  • How to attach boost::shared_ptr (or another smart pointer) to reference counter of object's parent?

    - by Checkers
    I remember encountering this concept before, but can't find it in Google now. If I have an object of type A, which directly embeds an object of type B: class A { B b; }; How can I have a smart pointer to B, e. g. boost::shared_ptr<B>, but use reference count of A? Assume an instance of A itself is heap-allocated I can safely get its shared count using, say, enable_shared_from_this.

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  • Are memory barriers necessary for atomic reference counting shared immutable data?

    - by Dietrich Epp
    I have some immutable data structures that I would like to manage using reference counts, sharing them across threads on an SMP system. Here's what the release code looks like: void avocado_release(struct avocado *p) { if (atomic_dec(p->refcount) == 0) { free(p->pit); free(p->juicy_innards); free(p); } } Does atomic_dec need a memory barrier in it? If so, what kind of memory barrier? Additional notes: The application must run on PowerPC and x86, so any processor-specific information is welcomed. I already know about the GCC atomic builtins. As for immutability, the refcount is the only field that changes over the duration of the object.

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  • How do I reference members of a single object passed to the View?

    - by Juxtaposed
    I'm new to MVC2 in ASP.NET/C#, so please forgive me if I misunderstand something. I have code similar to this in my Controller: var singleInstance = new Person("John"); ViewData["myInstance"] = singleInstance; return View(); So in my view, Index.aspx, I want to be able to reference members in that object. For example, Person has a member called Name, which is set in the constructor. In the view I want to get Person.Name from what is stored in the ViewData object. Ex.: <%= ViewData["myInstance"].name %> That doesn't work. The only real workaround I've found is to do something like this: <% var thePerson = ViewData["myInstance"]; print (or whatever the method is) thePerson.Name; %> Any help would be much appreciated... This was so much easier in PHP/Zend Framework... sigh

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  • Visual studio do not add my Component (from a dll) to the toolbox even if I reference it

    - by Fire-Dragon-DoL
    As stated in the title, I copied my dll in visual studio project, set it to "content" and "copy always". Added a reference to this dll and set it to "copy locally". I successfully managed to instance my component to a form through code but it doesn't appear in the toolbox, really boring. How can I solve this issue? If I link directly the dll project to this project it works, but now I'm treating the dll as "external" so it's not part of the same solution of the dll project. Thanks for any help

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  • Is there a way to reference a certain class/interface/... by enclosing it with its namespace rather than a using directive "using namespace_name" ?!

    - by Ahmed
    Is there a way to reference a certain class/interface/... by enclosing it with its namespace rather than a using directive "using namespace_name" ?! As, I'm working on a website, which uses SAP .NET connector. I already added a reference for connector ddl, and while referencing its namespace "using namespace_name", or set class namespace to another one rather than connector namespace, I got error regarding connector classes with that error message "The type or namespace couldn't be found, are you missing a using directive or an assembly reference?". But while changing namespace name to connector namespace, everything is going well?! // Set namespace to be IDestinationConfiguration interface namespace. namespace SAP.Middleware.Connector { public class ConnectorConfiguration : IDestinationConfiguration { } } So, connector types forced me to set namespace of class to their namespace! Is this possible? If so, how?

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  • How do you pull the URL for an ASP.NET web reference from a configuration file in Visual Studio 2008

    - by Ian Robinson
    I have a web reference for our report server embedded in our application. The server that the reports live on could change though, and I'd like to be able to change it "on the fly" if necessary. I know I've done this before, but can't seem to remember how. Thanks for your help. update - I've manually driven around this for the time being. It's not a big deal to set the URL in the code, but I'd like to figure out what the "proper" way of doing this in VS 2008 is. Could anyone provide any further insights? Thanks!

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  • Why is REMOTE_ADDR only sometimes available as an Apache environment variable?

    - by Xiong Chiamiov
    To avoid having to parse X-Forwarded-For in Varnish, I'm trying to just set a header on the SSL terminator (currently Apache) that stores the direct client IP in a header. On our development machine, this works: RequestHeader set X-Foo %{REMOTE_ADDR}e However, in staging it doesn't. Specifically, the header is empty, as illustrated by both varnishlog: 13 TxHeader b X-Foo: (null) (On the development machine, this shows the IP address as expected.) Similarly, logging REMOTE_ADDR shows that it only appears to be populated on the dev machine: # Config LogFormat "%{X-Forwarded-For}i %{REMOTE_ADDR}e" combined CustomLog "/var/log/httpd/access_log" combined # Log file, staging <my ip> - # Log file, development <my ip> <my ip> Since the dev machine is, well, a dev machine, it is different in a number of ways; however, I can't track down which difference is causing this. The versions of Apache are the same (2.2.22), and I don't see anything relevant in any of the standard config files or /etc/sysconfig/httpd. And the rest of the system is reasonably similar, since they're built off the same CentOS 5 base image. I can't even tell from the Apache documentation whether REMOTE_ADDR is expected to exist or not as an environment variable, but it clearly works on one machine, whether by fluke or design, and the inconsistency is driving me mad.

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  • Is it a good practice to create a reference to application context and use it anywhere?

    - by kknight
    I have to use context in many places of my code such as database operations, preference operations, etc. I don't want to pass in context for every method. Is it a good practice to create a reference to application context at the main Activity and use it anywhere such as database operations? So, I don't need some many context in method parameters, and the code can avoid position memory leak due to use of Activity Context. public class MainActivity extends Activity { public static Context s_appContext; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); s_appContext = this.getApplicationContext();

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  • Should I use a modified singleton design pattern that only allows one reference to its instance?

    - by Graham
    Hi, I have a class that would normally just generate factory objects, however this class should only used once throughout the program in once specifix place. What is the best design pattern to use in this instance? I throught that having a modified singleton design which only allows one reference to instance throughout the program would be the correct way to go. So only the first call to getInstance() returns the factory library. Is this a good or bad idea? Have I missed out another fundermental design pattern for solving this problem? Thanks for your help.

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  • What if I made an explicit reference to 'this' for use inside an inner class?

    - by badp
    So far, I've used this approach to access this from the scope of an inner class: class FooManagementWindow extends JFrame { JButton rejectFoo; //... void getFooAcceptingPanel(){ //... final FooManagementWindow referenceToThis = this; rejectFoo = new JButton("Reject"); rejectFoo.addEventListener(new EventListener() { @Override public void actionPerformed(ActionEvent arg) { referenceToThis.setEnabled(false); //this requires a network call //... referenceToThis.setEnabled(true); //the user may resume his work } }); //... } } However, I just learned that instead of declaring referenceToThis, a direct reference is kept for me as: FooManagementWindow.this I have no reason to think my less standard approach may lead to errors or weird corner cases. Or are there?

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  • Inheritance: possible to change base reference to something else?

    - by fred
    For example I have two classes, Base and Derived as shown below: class Base { public string Name { get; set; } public Base() { } } class Derived : Base { public Derived(Base b) { base = b; // doesn't compile, but is there any way to do something similar? } } So that they behave like this: Base b = new Base(); b.Name = "Bob"; Derived d = new Derived(b); d.Name = "John"; // b.Name is now "John" also Is this possible? I guess one way would be to keep the Base b reference in Derived and override Derived.Name to point to b.Name? Is there an easier way though, for example if I have like 50 properties to override? class Derived : Base { Base b; public override string Name { get { return b.Name; } set { b.Name = value; } } public Derived(Base b) { this.b = b; } }

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  • How to pass and set a CGFloat by reference?

    - by mystify
    I want to make an method which takes an CGFloat by reference. Could I do something like this? - (void)doStuff:(CGFloat*)floatPointer I guess this must look different than other object pointers which have two of those stars. Also I'm not sure if I must do something like: - (void)doStuff:(const CGFloat*)floatPointer And of course, no idea how to assign an CGFloat value to that floatPointer. Maybe &floatPointer = 5.0f; ? Could someone give some examples and explain these? Would be great!

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  • Is it possible to use a back reference to specify the number of replications in a regular expression

    - by user307894
    Is it possible to use a back reference to specify the number of replications in a regular expression? foo= 'ADCKAL+2AG.+2AG.+2AG.+2AGGG+.+G+3AGGa4.' The substrings that start with '+[0-9]' followed by '[A-z]{n}.' need to be replaced with simply '+' where the variable n is the digit from earlier in the substring. Can that n be back referenced? For example (doesn't work) '+([0-9])[A-z]{/1}.' is the pattern I want replaced with "+" (that last dot can be any character and represents a quality score) so that foo should come out to ADCKAL++++G.G+. foo = 'ADCKAL+2AG.+2AG.+2AG.+2AGGG^+.+G+3AGGa4.' indelpatt = re.compile('\+([0-9])') while indelpatt.search(foo): indelsize=int(indelpatt.search(foo).group(1)) new_regex = '\+%s[ACGTNacgtn]{%s}.' % (indelsize,indelsize) newpatt=re.compile(new_regex) foo = newpatt.sub("+", foo) I'm probably missing an easier way to parse the string.

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  • Simple php if query to double check

    - by skarama
    Is anything wrong with this code? <?php $variable = ; if (isset($variable)) { echo $variable ; echo "also this" ; } else echo "The variable is not set" ; ?> also, the other potential value of the variable is : $variable = <a href="http://www.mysite.com/article">This Article</a>; To clarify, I have a variable that may hold one of two possible values : an a href tag with it's url, or notihng at all. I need to have two different printouts for each of these cases, maybe I'm not doing it the right way though!

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  • C++0x: how to get variadic template parameters without reference?

    - by Sydius
    Given the following contrived (and yes, terrible) example: template<typename... Args> void something(Args... args) { std::tuple<Args...> tuple; // not initializing for sake of example std::get<0>(tuple) = 5; } It works if you call it like so: int x = 10; something<int>(x); However, it does not work if you call it like this: int x = 10; something<int&>(x); Because of the assignment to 5. Assuming that I cannot, for whatever reason, initialize the tuple when it is defined, how might I get this to work when specifying the type as a reference? Specifically, I would like the tuple to be std::tuple<int> even when Args... is int&.

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  • How do I reference a pointer from a different class?

    - by Justagruvn
    First off, I despise singletons with a passion. Though I should probably be trying to use one, I just don't want to. I want to create a data class (that is instantiated only once by a view controller on loading), and then using a different class, message the crap out of that data instance until it is brimming with so much data, it smiles. So, how do I do that? I made a pointer to the instance of the data class when I instantiated it. I'm now over in a separate view controller, action occurs, and I want to update the initial data object. I think I need to reference that object by way of pointer, but I have no idea how to do that. Yes, I've set properties and getters and setters, which seem to work, but only in the initial view controller class. Peace Love applesauce.

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  • How to reference/link another project in grails workspace without using jar files?

    - by Ivan Alagenchev
    I have a Grails website that references a java core application. I have been successful in adding a .jar dependency to that project; however the java project is in the same workspace as my grails project and I would ultimately like to reference that project directly. I don't want to deal with the added step of creating a new jar file every time that there is a modification to the java project, cleaning and updating my dependencies. I added the java project to my grails' project "Java Build Path" and at first everything seemed to work fine, but when I run grailscompile, the compiler fails to resolve all imports that point to the java project. I am using Spring Source Toolsuite as my IDE.

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  • How do i get (is it possible to) a reference to the class that creates an instance of another class.

    - by Cadde
    Odd situation... I need to create a new instance of a class that needs a member of the calling class. But i can't pass a reference to the calling class through the constructor. The solution i am looking for is something like this: Public Class ChildClass Public Sub New(args) _MyMember = GetMemberFromCallingClass() ... ... End Sub End Class I want this to work without having to manually pass any references or variables from the calling class to the new instance of ChildClass. Is this possible and if so, what should i look at to make this part of my code.

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  • Checking for a session variable... returns (Object reference not set to an instance of an object.)

    - by Chocol8
    In the Session_Start i have Sub Session_Start(ByVal sender As Object, ByVal e As EventArgs) Session("login") = False End Sub and in a custom .aspx page i included the following... Public ReadOnly Property GetLoginState() As Boolean Get If Current.Session("login") Is Nothing Then Current.Session("login") = False End If Return Current.Session("login") End Get End Property Why i am getting error the error Object reference not set to an instance of an object. at line If Current.Session("login") Is Nothing Then while checking for the login state as follows? If GetLogin = False Then 'Do something End if I mean i have already created the instance on the Session_Start... Haven't i? What am i doing wrong here?

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  • Can we overload a function based on only whether a parameter is a value or a reference?

    - by skydoor
    I got the answer NO! Because passing by value and passing by reference looks identical to the caller. However, the code below compiles right class A { public: void f(int i) {} void f(int& i) {} }; But when I try to use it, there is compile error. int main () { A a; int i = 9; int& j = i; a.f(1); a.f(i); a.f(j); return 0; } Why does not the compiler disable it even without knowing it is going to be used?

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  • How Do I Reference An Element By Name With [] Brackets In It?

    - by user384030
    How do you reference a element in jquery BY NAME that has the [] in it. <select name="values[]" multiple="true"> <option value="1">1</option> <option value="2">2</option> <option value="2">2</option> </select> <script type="text/javascript"> $('[name=values[]]'); </script> this should grab the element, but it does not work, I believe the [] in the name is messing it up, escaping it doesn't seem to work either. I can't figure out what I'm doing wrong

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  • C#/.NET Little Pitfalls: The Dangers of Casting Boxed Values

    - by James Michael Hare
    Starting a new series to parallel the Little Wonders series.  In this series, I will examine some of the small pitfalls that can occasionally trip up developers. Introduction: Of Casts and Conversions What happens when we try to assign from an int and a double and vice-versa? 1: double pi = 3.14; 2: int theAnswer = 42; 3:  4: // implicit widening conversion, compiles! 5: double doubleAnswer = theAnswer; 6:  7: // implicit narrowing conversion, compiler error! 8: int intPi = pi; As you can see from the comments above, a conversion from a value type where there is no potential data loss is can be done with an implicit conversion.  However, when converting from one value type to another may result in a loss of data, you must make the conversion explicit so the compiler knows you accept this risk.  That is why the conversion from double to int will not compile with an implicit conversion, we can make the conversion explicit by adding a cast: 1: // explicit narrowing conversion using a cast, compiler 2: // succeeds, but results may have data loss: 3: int intPi = (int)pi; So for value types, the conversions (implicit and explicit) both convert the original value to a new value of the given type.  With widening and narrowing references, however, this is not the case.  Converting reference types is a bit different from converting value types.  First of all when you perform a widening or narrowing you don’t really convert the instance of the object, you just convert the reference itself to the wider or narrower reference type, but both the original and new reference type both refer back to the same object. Secondly, widening and narrowing for reference types refers the going down and up the class hierarchy instead of referring to precision as in value types.  That is, a narrowing conversion for a reference type means you are going down the class hierarchy (for example from Shape to Square) whereas a widening conversion means you are going up the class hierarchy (from Square to Shape).  1: var square = new Square(); 2:  3: // implicitly convers because all squares are shapes 4: // (that is, all subclasses can be referenced by a superclass reference) 5: Shape myShape = square; 6:  7: // implicit conversion not possible, not all shapes are squares! 8: // (that is, not all superclasses can be referenced by a subclass reference) 9: Square mySquare = (Square) myShape; So we had to cast the Shape back to Square because at that point the compiler has no way of knowing until runtime whether the Shape in question is truly a Square.  But, because the compiler knows that it’s possible for a Shape to be a Square, it will compile.  However, if the object referenced by myShape is not truly a Square at runtime, you will get an invalid cast exception. Of course, there are other forms of conversions as well such as user-specified conversions and helper class conversions which are beyond the scope of this post.  The main thing we want to focus on is this seemingly innocuous casting method of widening and narrowing conversions that we come to depend on every day and, in some cases, can bite us if we don’t fully understand what is going on!  The Pitfall: Conversions on Boxed Value Types Can Fail What if you saw the following code and – knowing nothing else – you were asked if it was legal or not, what would you think: 1: // assuming x is defined above this and this 2: // assignment is syntactically legal. 3: x = 3.14; 4:  5: // convert 3.14 to int. 6: int truncated = (int)x; You may think that since x is obviously a double (can’t be a float) because 3.14 is a double literal, but this is inaccurate.  Our x could also be dynamic and this would work as well, or there could be user-defined conversions in play.  But there is another, even simpler option that can often bite us: what if x is object? 1: object x; 2:  3: x = 3.14; 4:  5: int truncated = (int) x; On the surface, this seems fine.  We have a double and we place it into an object which can be done implicitly through boxing (no cast) because all types inherit from object.  Then we cast it to int.  This theoretically should be possible because we know we can explicitly convert a double to an int through a conversion process which involves truncation. But here’s the pitfall: when casting an object to another type, we are casting a reference type, not a value type!  This means that it will attempt to see at runtime if the value boxed and referred to by x is of type int or derived from type int.  Since it obviously isn’t (it’s a double after all) we get an invalid cast exception! Now, you may say this looks awfully contrived, but in truth we can run into this a lot if we’re not careful.  Consider using an IDataReader to read from a database, and then attempting to select a result row of a particular column type: 1: using (var connection = new SqlConnection("some connection string")) 2: using (var command = new SqlCommand("select * from employee", connection)) 3: using (var reader = command.ExecuteReader()) 4: { 5: while (reader.Read()) 6: { 7: // if the salary is not an int32 in the SQL database, this is an error! 8: // doesn't matter if short, long, double, float, reader [] returns object! 9: total += (int) reader["annual_salary"]; 10: } 11: } Notice that since the reader indexer returns object, if we attempt to convert using a cast to a type, we have to make darn sure we use the true, actual type or this will fail!  If the SQL database column is a double, float, short, etc this will fail at runtime with an invalid cast exception because it attempts to convert the object reference! So, how do you get around this?  There are two ways, you could first cast the object to its actual type (double), and then do a narrowing cast to on the value to int.  Or you could use a helper class like Convert which analyzes the actual run-time type and will perform a conversion as long as the type implements IConvertible. 1: object x; 2:  3: x = 3.14; 4:  5: // if you want to cast, must cast out of object to double, then 6: // cast convert. 7: int truncated = (int)(double) x; 8:  9: // or you can call a helper class like Convert which examines runtime 10: // type of the value being converted 11: int anotherTruncated = Convert.ToInt32(x); Summary You should always be careful when performing a conversion cast from values boxed in object that you are actually casting to the true type (or a sub-type). Since casting from object is a widening of the reference, be careful that you either know the exact, explicit type you expect to be held in the object, or instead avoid the cast and use a helper class to perform a safe conversion to the type you desire. Technorati Tags: C#,.NET,Pitfalls,Little Pitfalls,BlackRabbitCoder

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