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Is there any difference between “foo is None” and “foo == None”?
...is ultimately determined by the __eq__() method
i.e.
>>> class Foo(object):
def __eq__(self, other):
return True
>>> f = Foo()
>>> f == None
True
>>> f is None
False
...
Can I call a constructor from another constructor (do constructor chaining) in C++?
...legating constructors).
The syntax is slightly different from C#:
class Foo {
public:
Foo(char x, int y) {}
Foo(int y) : Foo('a', y) {}
};
C++03: No
Unfortunately, there's no way to do this in C++03, but there are two ways of simulating this:
You can combine two (or more) constructors v...
How can I join elements of an array in Bash?
...y , a "b c" d #a,b c,d
join_by / var local tmp #var/local/tmp
join_by , "${FOO[@]}" #a,b,c
This solution is based on Pascal Pilz's original suggestion.
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What is “lifting” in Haskell?
...
Typically you have some data type with a parameter. Something like
data Foo a = Foo { ...stuff here ...}
Suppose you find that a lot of uses of Foo take numeric types (Int, Double etc) and you keep having to write code that unwraps these numbers, adds or multiplies them, and then wraps them bac...
Getters \ setters for dummies
...properties. They work with all modern browsers except IE 8 and below.
var foo = {
bar : 123,
get bar(){ return bar; },
set bar( value ){ this.bar = value; }
};
foo.bar = 456;
var gaz = foo.bar;
Custom Getters and Setters
get and set aren't reserved words, so they can be overloaded to...
Is it possible to clone html element objects in JavaScript / JQuery?
...n copy children of one element and paste them into the other element:
var foo1 = jQuery('#foo1');
var foo2 = jQuery('#foo2');
foo1.html(foo2.children().clone());
Proof: http://jsfiddle.net/de9kc/
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What is the 'override' keyword in C++ used for? [duplicate]
...errides.
To explain the latter:
class base
{
public:
virtual int foo(float x) = 0;
};
class derived: public base
{
public:
int foo(float x) override { ... } // OK
}
class derived2: public base
{
public:
int foo(int x) override { ... } // ERROR
};
In derived2 the compi...
What are some (concrete) use-cases for metaclasses?
...ase classes' attributes every time):
>>> class A(Model):
... foo = Integer()
...
>>> class B(A):
... bar = String()
...
>>> B._fields
{'foo': Integer('A.foo'), 'bar': String('B.bar')}
Again, this can be done (without inheritance) with a class decorator:
def mod...
Overriding a Rails default_scope
...
In Rails 3:
foos = Foo.unscoped.where(:baz => baz)
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PHP Fatal error: Using $this when not in object context
...
In my index.php I'm loading maybe
foobarfunc() like this:
foobar::foobarfunc(); // Wrong, it is not static method
but can also be
$foobar = new foobar; // correct
$foobar->foobarfunc();
You can not invoke method this way because it is not sta...