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Why do we need virtual functions in C++?
... virtual modifier on/off to see what happens
//virtual
std::string Says() { return "?"; }
};
class Dog: public Animal
{
public: std::string Says() { return "Woof"; }
};
void test()
{
Dog* d = new Dog();
Animal* a = d; // refer to Dog instance with Animal pointer
...
What is JavaScript garbage collection?
...called a "scavenger". A scavenger
may refer to a number, an object, a
string, whatever. We maintain a list
of scavengers -- variables are moved
on to the scav list when they come
into scope and off the scav list when
they go out of scope.
Every now and then the garbage
collector ru...
Get time difference between two dates in seconds
...act them and divide by 1000 (since it's originally in milliseconds). As an extra, when you're calling the getDate() method, you're in fact getting the day of the month as an integer between 1 and 31 (not zero based) as opposed to the epoch time you'd get from calling the getTime() method, representi...
How can I check for “undefined” in JavaScript? [duplicate]
...e undefined, then use the typeof operator, which is guaranteed to return a string:
if (typeof myVar !== 'undefined')
Direct comparisons against undefined are troublesome as undefined can be overwritten.
window.undefined = "foo";
"foo" == undefined // true
As @CMS pointed out, this has been pa...
Event on a disabled input
...vidual container of its own, if they aren't already laid out that way - an extra <span> or a <div>, say - just to make it easy to distinguish which disabled input was clicked).
The downside is that this trick unfortunately won't works for older browsers that don't support the pointer-...
When to use ref and when it is not necessary in C#
...ltiple return values create structs'). Take for example IPAddress.TryParse(string, out IPAddress).
– Swen Kooij
Dec 6 '13 at 21:47
...
C default arguments
... present depending on the required arguments, and printf(3) reads a format string that specifies how many arguments there will be. Both use varargs quite safely and effectively, and though you can certainly screw them up, printf() especially seems to be quite popular.
– Chris L...
What is “rvalue reference for *this”?
... within this heterogeneous set, a member function is considered to have an extra parameter, called the implicit object parameter, which represents the object for which the member function has been called. [...]
p3 Similarly, when appropriate, the context can construct an argument list that contains ...
How does #include work in C++? [duplicate]
... words it's perfectly legal for an implementation to declare the name std::string directly or indirectly when using #include <vector>).
Despite this however you are required by the language to know and tell the compiler which standard header includes which part of the standard library. This i...
The tilde operator in Python
...o so before supplying an __invert__ method to your class. (Note that byte-strings [ex: '\xff'] do not support this operator, even though it is meaningful to invert all the bits of a byte-string.)
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