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  • Proc.new vs Lambda in Ruby

    - by piemesons
    Plese check this: def foo f = Proc.new { return "return from foo from inside proc" } f.call # control leaves foo here return "return from foo" end def bar f = lambda { return "return from lambda" } f.call # control does not leave bar here return "return from bar" end puts foo # prints "return from foo from inside proc" puts bar # prints "return from bar" Can anybody tell me what lambda is and what is Proc and whats the difference.

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  • Are incremental Macro definition possible?

    - by Davorak
    I often find the following type of incremental definition useful: (define (foo) (display "bar")) (foo) ;prints bar (define foo (let ((bar foo)) (lambda () (display "foo") (bar)))) (foo) ;prints foobar How do I preform this type of incremental definition with macros? I could not get let-syntax to provide the same functionality. Currently I use plt scheme, but would like to see answers in different lisp implementations as well.

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  • What's the correct way to pass parameters from VBScript to COM interface implemented in C#?

    - by nopopem
    I'm trying to expose a fairly simple C# class to COM which should be usable from VBScript (among others). Some objects need to be created via COM calls and will be used in furter calls later on. The definition of the exposed classes and interfaces looks like this: namespace Test { [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] public interface IComInterface { IFoo CreateFoo(); void UseFoo(int x, IFoo f); } [ClassInterface(ClassInterfaceType.None)] public sealed class CComInterface : IComInterface { public CComInterface() {} public IFoo CreateFoo() { return new Foo(); } public void UseFoo(int x, IFoo f) { f.Bar(); } } [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] public interface IFoo { void Bar(); } [ClassInterface(ClassInterfaceType.None)] public class Foo : IFoo { internal Foo() {} public void Bar() {} } } The simplest thinkable COM client in VBScript does this: Dim ci Set ci = WScript.CreateObject("Test.CComInterface") Dim foo Set foo = ci.CreateFoo foo.Bar ci.UseFoo 0, foo While the call to Bar succeeds, calling UseFoo fails with "Error 5: invalid procedure call or invalid argument" The generated IDL seems ok to me: dispinterface IComInterface { properties: methods: [id(0x60020003)] IFoo* CreateFoo(); [id(0x60020004)] void UseFoo( [in] long x, [in] IFoo* f); }; The vbs call succeeds when I wrap the second parameter in parentheses like this: ci.UseFoo 0, (foo) As far as I understand (I'm no VBScript expert however) this forces the reference to foo to be passed by value, i.e. a copy of the reference is being made. How can I change the interface so that it can be called with the foo reference directly? Since this will be a public interface used by customers I don't like the idea of having to explain why all the objects created need to be passed back in an extra pair of parentheses...

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  • How to condense a path in C++ using Boost?

    - by pdillon3
    Does Boost offer a simple way to condense a path such as /foo/bar/../bar or /foo/../. into the absolute path it refers to. /foo/bar/../bar -- /foo/bar /foo/../. -- / The goal is to combine base_path and rel_path with boost::filesystem::complete(rel_path, base_path) into a path into /foo/bar/with/no/dots. thanks

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  • how to structure code that uses std::rel_ops

    - by R Samuel Klatchko
    I was working on some code and wanted to make use of std::rel_ops. From what I can tell, you need to do using std::rel_ops to your source code to make use of them. But I'm not sure where the best place to put that is. Let's say I have a header file with a class that only defines the minimal operator== and operator<: // foo.h class foo { public: bool operator==(const foo &other) const; bool operator<(const foo &other) const; }; I'm not sure where to put using std::rel_ops. If I leave it out of the foo.h, then every user of foo.h needs to know the implementation detail that foo is not defining all the operators itself. But putting using std::rel_ops inside foo.h breaks the rule of thumb about not having a using in a header file. How do other people resolve this issue?

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  • How do you get SQLAlchemy to override MySQL "on update CURRENT_TIMESTAMP"

    - by nocola
    I've inherited an older database that was setup with a "on update CURRENT_TIMESTAMP" put on a field that should only describe an item's creation. With PHP I have been using "timestamp=timestamp" on UPDATE clauses, but in SQLAlchemy I can't seem to force the system to use the set timestamp. Do I have no choice and need to update the MySQL table (millions of rows)? foo = session.query(f).get(int(1)) ts = foo.timestamp setattr(foo, 'timestamp', ts) setattr(foo, 'bar', bar) www_model.www_Session.commit() I have also tried: foo = session.query(f).get(int(1)) setattr(foo, 'timestamp', foo.timestamp) setattr(foo, 'bar', bar) www_model.www_Session.commit()

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  • FRIEND_TEST in Google Test - possible circular dependency?

    - by Mihaela
    I am trying to figure out how FRIEND_TEST works in Google Tests. http://code.google.com/p/googletest/wiki/AdvancedGuide#Private_Class_Members I am looking at the following item, trying to implement it in my code: // foo.h #include "gtest/gtest_prod.h" // Defines FRIEND_TEST. class Foo { ... private: FRIEND_TEST(FooTest, BarReturnsZeroOnNull); int Bar(void* x); }; // foo_test.cc ... TEST(FooTest, BarReturnsZeroOnNull) { Foo foo; EXPECT_EQ(0, foo.Bar(NULL)); // Uses Foo's private member Bar(). } In the code above, the piece that I can't see, is that foo_test.cc must include foo.h, in order to have access to Foo and Bar(). [Perhaps it works differently for Google ? in my code, I must include it] That will result in circular dependency... Am I missing something ?

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  • Howoto get id of new record after model.save

    - by tonymarschall
    I have a model with the following db structure: mysql> describe units; +------------+----------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+----------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(128) | NO | | NULL | | | created_at | datetime | NO | | NULL | | | updated_at | datetime | NO | | NULL | | +------------+----------+------+-----+---------+----------------+ 7 rows in set (0.00 sec) After creating a new record an saving i can not get the id of the record. 1.9.3p194 :001 > unit = Unit.new(:name => 'test') => #<Unit id: nil, name: "test", created_at: nil, updated_at: nil> 1.9.3p194 :002 > unit.save (0.2ms) BEGIN SQL (0.3ms) INSERT INTO `units` (`created_at`, `name`, `updated_at`) VALUES ('2012-08-31 23:48:12', 'test', '2012-08-31 23:48:12') (144.6ms) COMMIT => true 1.9.3p194 :003 > unit.inspect => "#<Unit id: nil, name: \"test\", created_at: \"2012-08-31 23:48:12\", updated_at: \"2012-08-31 23:48:12\">" # unit.rb class Unit < ActiveRecord::Base attr_accessible :name end # migration class CreateUnits < ActiveRecord::Migration def change create_table :units do |t| t.string :name, :null => false t.timestamps end end end Tried this with other models and have the same result (no id). Data is definitily saved and i can get data with Unit.last Another try with Foo.id = nil # /var/www# rails g model Foo name:string invoke active_record create db/migrate/20120904030554_create_foos.rb create app/models/foo.rb invoke test_unit create test/unit/foo_test.rb create test/fixtures/foos.yml # /var/www# rake db:migrate == CreateFoos: migrating ===================================================== -- create_table(:foos) -> 0.3451s == CreateFoos: migrated (0.3452s) ============================================ # /var/www# rails c Loading development environment (Rails 3.2.8) 1.9.3p194 :001 > foo = Foo.new(:name => 'bar') => #<Foo id: nil, name: "bar", created_at: nil, updated_at: nil> 1.9.3p194 :002 > foo.save (0.2ms) BEGIN SQL (0.4ms) INSERT INTO `foos` (`created_at`, `name`, `updated_at`) VALUES ('2012-09-04 03:06:26', 'bar', '2012-09-04 03:06:26') (103.2ms) COMMIT => true 1.9.3p194 :003 > foo.inspect => "#<Foo id: nil, name: \"bar\", created_at: \"2012-09-04 03:06:26\", updated_at: \"2012-09-04 03:06:26\">" 1.9.3p194 :004 > Foo.last Foo Load (0.5ms) SELECT `foos`.* FROM `foos` ORDER BY `foos`.`id` DESC LIMIT 1 => #<Foo id: 1, name: "bar", created_at: "2012-09-04 03:06:26", updated_at: "2012-09-04 03:06:26">

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  • Constant template parameter class manages to link externally

    - by the_drow
    I have a class foo with an enum template parameter and for some reason it links to two versions of the ctor in the cpp file. enum Enum { bar, baz }; template <Enum version = bar> class foo { public: foo(); }; // CPP File #include "foo.hpp" foo<bar>::foo() { cout << "bar"; } foo<baz>::foo() { cout << "baz"; } I'm using msvc 2008, is this the standard behavior? Are only type template parameters cannot be linked to cpp files?

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  • Is incremental Macro definition possible?

    - by Davorak
    I often find the following type of incremental definition useful: (define (foo) (display "bar")) (foo) ;prints bar (define foo (let ((bar foo)) (lambda () (display "foo") (bar)))) (foo) ;prints foobar How do I preform this type of incremental definition with macros? I could not get let-syntax to provide the same functionality. Currently I use plt scheme, but would like to see answers in different lisp implementations as well.

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  • C++ STL: How to iterate vector while requiring access to element and its index?

    - by Ashwin
    I frequently find myself requiring to iterate over STL vectors. While I am doing this I require access to both the vector element and its index. I used to do this as: typedef std::vector<Foo> FooVec; typedef FooVec::iterator FooVecIter; FooVec fooVec; int index = 0; for (FooVecIter i = fooVec.begin(); i != fooVec.end(); ++i, ++index) { Foo& foo = *i; if (foo.somethingIsTrue()) // True for most elements std::cout << index << ": " << foo << std::endl; } After discovering BOOST_FOREACH, I shortened this to: typedef std::vector<Foo> FooVec; FooVec fooVec; int index = -1; BOOST_FOREACH( Foo& foo, fooVec ) { ++index; if (foo.somethingIsTrue()) // True for most elements std::cout << index << ": " << foo << std::endl; } Is there a better or more elegant way to iterate over STL vectors when both reference to the vector element and its index is required? I am aware of the alternative: for (int i = 0; i < fooVec.size(); ++i) But I keep reading about how it is not a good practice to iterate over STL containers like this.

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  • c++ protected pointer member to the same class and access privileges

    - by aajmakin
    Hi, Example code is included at the bottom of the message. I'm puzzled about the protected access specifier in a class. I have define a class node which has a protected string member name string name; and a vector of node pointers vector args; Before I thought that a member function of node could not do args[0]-name but a program that does just this does compile and run. However, now I would like to inherit this class and access the name field in one of the args array pointers from this derived class args[0]-name but this does not compile. When I compile the example code below with the commented sections uncommented, the compiler reports: Compiler output: g++ test.cc -o test test.cc: In member function 'void foo::newnode::print_args2()': test.cc:22: error: 'std::string foo::node::name' is protected test.cc:61: error: within this context Compilation exited abnormally with code 1 at Thu Jun 17 12:40:12 Questions: Why can I access the name field of the node pointers in args in class node, because this is what I would excpect from a similarly defined private field in Java. How can I access those fields from the derived class. Example code: #include <iostream> #include <vector> using namespace std; namespace foo { class node; typedef std::vector<node*> nodes; class node { public: node (string _name); void print_args (); void add_node (node* a); protected: nodes args; string name; }; } foo::node::node (string _name) : args(0) { name = _name; } void foo::node::add_node (node* a) { args.push_back(a); } void foo::node::print_args () { for (int i = 0; i < args.size(); i++) { cout << "node " << i << ": " << args[i]->name << endl; } } // namespace foo // { // class newnode : public node // { // public: // newnode (string _name) : node(_name) {} // void print_args2 (); // protected: // }; // } // void foo::newnode::print_args2 () // { // for (int i = 0; i < args.size(); i++) // { // cout << "node " << i << ": " << args[i]->name << endl; // } // } int main (int argc, char** argv) { foo::node a ("a"); foo::node b ("b"); foo::node c ("c"); a.add_node (&b); a.add_node (&c); a.print_args (); // foo::newnode newa ("newa"); // foo::newnode newb ("newb"); // foo::newnode newc ("newc"); // newa.add_node (&newb); // newa.add_node (&newc); // newa.print_args2 (); return 0; }

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  • Callable objects on ActionScript?

    - by CodexDraco
    Hi, is it posible to have callable objects on ActionScript? For example: class Foo extends EventDispatcher { Foo() { super(); } call(world:String):String { return "Hello, " + world; } } And later... var foo:Foo = new Foo(); trace( foo("World!") ); // Will NOT work

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  • To use package properly, how to arrange directory, file name, unit test file?

    - by Stephen Hsu
    My source files tree is like this: /src /pkg /foo foo.go foo_test.go Inside foo.go: package foo func bar(n int) { ... } inside foo_test.go: package foo func testBar(t *testing.T) { bar(10) ... } My questions are: Does package name relates to directory name, source file name? If there is only one source file for a package, need I put it in a directory? Should I put foo.go and foo_test.go in the same package? In the foo_test.go, as it's in the same package as foo.go, I didn't import foo. But when I compile foo_test.go with 6g, it says bar() is undefined. What should I do?

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  • Silverlight: Binding to a LayoutRoot value from within a DataTemplate

    - by Rosarch
    I have a DataTemplate for a ListBox, where I have several controls that bind to an item. I would also like to bind to a value on LayoutRoot.DataContext. I'm unsure of how to do this. <!--LayoutRoot is the root grid where all page content is placed--> <StackPanel x:Name="LayoutRoot" Background="Transparent"> <ListBox ItemsSource="{Binding Items}"> <ListBox.ItemTemplate> <DataTemplate> <StackPanel> <TextBlock Text="{Binding}" /> <TextBlock Text="{Binding ElementName=LayoutRoot, Path=DataContext.Foo}" /> </StackPanel> </DataTemplate> </ListBox.ItemTemplate> </ListBox> </StackPanel> public partial class MainPage : PhoneApplicationPage { public string Foo { get { return "the moon"; } } private int startIndex = 1; private IList<string> _data = new List<string>() { "foo", "bar", "baz" }; public IList<string> Items { get { return _data; } } // Constructor public MainPage() { InitializeComponent(); LayoutRoot.DataContext = this; } } This doesn't work; only the _data items are displayed. The following binding errors appear in the Debug output: System.Windows.Data Error: BindingExpression path error: 'Foo' property not found on 'foo' 'System.String' (HashCode=1502598398). BindingExpression: Path='DataContext.Foo' DataItem='System.Windows.Controls.Border' (HashCode=78299055); target element is 'System.Windows.Controls.TextBlock' (Name=''); target property is 'Text' (type 'System.String').. System.Windows.Data Error: BindingExpression path error: 'Foo' property not found on 'bar' 'System.String' (HashCode=696029481). BindingExpression: Path='DataContext.Foo' DataItem='System.Windows.Controls.Border' (HashCode=78298703); target element is 'System.Windows.Controls.TextBlock' (Name=''); target property is 'Text' (type 'System.String').. System.Windows.Data Error: BindingExpression path error: 'Foo' property not found on 'baz' 'System.String' (HashCode=696029489). BindingExpression: Path='DataContext.Foo' DataItem='System.Windows.Controls.Border' (HashCode=78298694); target element is 'System.Windows.Controls.TextBlock' (Name=''); target property is 'Text' (type 'System.String').. Do I have a syntax error somewhere? Update I'm aiming for something that looks like this: foo the moon bar the moon baz the moon Instead, all I'm getting is: foo bar baz

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  • java.lang.ClassNotFoundException error using enum as a key in Map

    - by LCYSoft
    <util:map id="myMap" key-type="com.myClass.Foo.myEnum" value-type="com.myClass.Foo"> <entry> <key> <value type="com.myClass.Foo.myEnum">ONE</value> </key> <ref bean="myObj"/> </entry> </util:map> package com.myClass public class Foo { public enum myEnum {ONE, TWO;} } I am trying to create a map from Spriong 2.5. Map<myEnum, Foo> myMap; I am getting nested exception is java.lang.ClassNotFoundException:com.myClass.Foo.myEnum I definitely have com.myClass.Foo.myEnumin com.myClass.Foo I don't know why I am getting java.lang.ClassNotFoundException Thanks in advance

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  • Creating an instance within the Class itself

    - by didxga
    What's going on when the assignment statement executed at Line 4, does compiler ignore the new operator and keep the foo variable being null or something else happen to handle this awkward moment? public class Foo { // creating an instance before its constructor has been invoked, suppose the "initializing" // gets printed in constructor as a result of the next line, of course it will not print it private Foo foo = new Foo();//Line 4 public Foo() { System.out.println("initializing"); } }

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  • Friendness and derived class

    - by ereOn
    Hi, Let's say I have the following class hierarchy: class Base { protected: virtual void foo() = 0; friend class Other; }; class Derived : public Base { protected: void foo() { /* Some implementation */ }; }; class Other { public: void bar() { Derived* a = new Derived(); a->foo(); // Compiler error: foo() is protected within this context }; }; I guess I could change it too a->Base::foo() but since foo() is pure virtual in the Base class, the call will result in calling Derived::foo() anyway. However, the compiler seems to refuse a->foo(). I guess it is logical, but I can't really understand why. Am I missing something ? Can't (shouldn't) it handle this special case ? Thank you.

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  • php / phpDoc - @return instance of $this class ?

    - by searbe
    How do I mark a method as "returns an instance of the current class" in my phpDoc? In the following example my IDE (Netbeans) will see that setSomething always returns a foo object. But that's not true if I extent the object - it'll return $this, which in the second example is a bar object not a foo object. class foo { protected $_value = null; /** * Set something * * @param string $value the value * @return foo */ public function setSomething($value) { $this->_value = $value; return $this; } } $foo = new foo(); $out = $foo->setSomething(); So fine - setSomething returns a foo - but in the following example, it returns a bar..: class bar extends foo { public function someOtherMethod(){} } $bar = new bar(); $out = $bar->setSomething(); $out->someOtherMethod(); // <-- Here, Netbeans will think $out // is a foo, so doesn't see this other // method in $out's code-completion ... it'd be great to solve this as for me, code completion is a massive speed-boost. Anyone got a clever trick, or even better, a proper way to document this with phpDoc?

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  • Functions without arguments, with unit as argument in scala

    - by scout
    def foo(x:Int, f:Unit=>Int) = println(f()) foo(2, {Unit => 3+4} //case1 def loop:Int = 7 foo(2, loop) //does not compile changing loop to //case 2 def loop():Int = 7 foo(2, loop) // does not compile changing loop to //case 3 def loop(x:Unit): Int = 7 //changing according to Don's Comments foo(2,loop) // compiles and works fine should'nt case 1 and case 2 also work? why are they not working? defining foo as def foo(x:Int, y:()=>Int) then case 2 works but not case 1. Arent they all supposed to work, defining the functions either way. //also i think ()=Int in foo is a bad style, y:=Int does not work, comments??

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  • modify a method/function at runtime

    - by mononym
    I've been looking at the php reflection methods, what i want to do is inject some code after the method is opened and before any return value, for example i want to change: function foo($bar) { $foo = $bar ; return $foo ; } And inject some code into it like: function foo($bar) { //some code here $foo = $bar ; //some code here return $foo ; } possible?

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