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C++STL容器使用经验总结 - C/C++ - 清泛网 - 专注C/C++及内核技术
...至少不能未经过强制类型转换（转换到一个引用类型const_cast<T&>）就修改。
如果你想以一种总是可行而且安全的方式来许该set、multiset、map和multimap中的元素，则可以分5个简单步骤来进行：
1. 找到你想修改的容器的元素。如果...
How to set enum to null
...
@equiman no need to cast since the type is specified on the left, you are basically duplicating the first part of my answer that is already accepted.
– Rodney S. Foley
Jul 8 '15 at 22:50
...
Which one will execute faster, if (flag==0) or if (0==flag)?
...caveat: Nawaz did point out the user-defined trap. And I regret my hastily cast upvote on "stupidest question" because it seems that many did not get it right and it gives room for a nice discussion on compiler optimization :)
The answer is:
What is flag's type?
In the case where flag actuall...
Count the items from a IEnumerable without iterating?
...enumerator.MoveNext())
result++;
}
return result;
So it tries to cast to ICollection<T>, which has a Count property, and uses that if possible. Otherwise it iterates.
So your best bet is to use the Count() extension method on your IEnumerable<T> object, as you will get the bes...
round() for float in C++
....49999999999999994, (see it live).
Another common implementation involves casting a floating point type to an integral type, which can invoke undefined behavior in the case where the integral part can not be represented in the destination type. We can see this from the draft C++ standard section 4....
Double negation (!!) in javascript - what is the purpose? [duplicate]
...
It casts to boolean. The first ! negates it once, converting values like so:
undefined to true
null to true
+0 to true
-0 to true
'' to true
NaN to true
false to true
All other expressions to false
Then the other ! negates i...
How do you implement a class in C? [closed]
...s the proper class, i.e. RectangleClass *. This means you often have to do casts, but they provide handy macros do help with that, so you can always cast BASECLASS *p to SUBCLASS * using just SUBCLASS(p).
– unwind
Sep 10 '09 at 8:03
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Is null an Object?
...no
name, it is impossible to declare a
variable of the null type or to cast
to the null type. The null reference
is the only possible value of an
expression of null type. The null
reference can always be cast to any
reference type. In practice, the
programmer can ignore the null type...
Best way to convert IList or IEnumerable to Array
...omething like this:
IEnumerable query = ...;
MyEntityType[] array = query.Cast<MyEntityType>().ToArray();
If you don't know the type within that method but the method's callers do know it, make the method generic and try this:
public static void T[] PerformQuery<T>()
{
IEnumerabl...
Subclassing a Java Builder class
...
To solve the unchecked cast warning, see the solution suggested bellow among the other answers: stackoverflow.com/a/34741836/3114959
– Stepan Vavra
Jan 12 '16 at 11:00
...