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Round to 5 (or other number) in Python
...ndard function in Python, but this works for me:
Python 2
def myround(x, base=5):
return int(base * round(float(x)/base))
Python3
def myround(x, base=5):
return base * round(x/base)
It is easy to see why the above works. You want to make sure that your number divided by 5 is an integ...
C++ templates that accept only certain types
...
I suggest using Boost's static assert feature in concert with is_base_of from the Boost Type Traits library:
template<typename T>
class ObservableList {
BOOST_STATIC_ASSERT((is_base_of<List, T>::value)); //Yes, the double parentheses are needed, otherwise the comma will be...
Algorithms based on number base systems? [closed]
I've noticed recently that there are a great many algorithms out there based in part or in whole on clever uses of numbers in creative bases. For example:
...
new keyword in method signature
...:
You cannot override a non-virtual or
static method. The overridden base
method must be virtual, abstract, or
override.
So the 'new' keyword is needed to allow you to 'override' non-virtual and static methods.
s...
Downcasting shared_ptr to shared_ptr?
...amic_pointer_cast. It is supported by std::shared_ptr.
std::shared_ptr<Base> base (new Derived());
std::shared_ptr<Derived> derived =
std::dynamic_pointer_cast<Derived> (base);
Documentation: https://en.cppreference.com/w/cpp/memory/shared_ptr/pointer_cast
Also, ...
App Inventor 2 上传文件和图片到服务器教程 · App Inventor 2 中文网
...传
3. 处理上传结果
方案二：Base64 编码上传
原理
组件准备
积木块代码
1. 读取文件并 Base64 编码上传
2. 处理上传结果（同方案一）
服务器端代...
What is base 64 encoding used for?
I've heard people talking about "base 64 encoding" here and there. What is it used for?
18 Answers
...
How to use base class's constructors and assignment operator in C++?
...
You can explicitly call constructors and assignment operators:
class Base {
//...
public:
Base(const Base&) { /*...*/ }
Base& operator=(const Base&) { /*...*/ }
};
class Derived : public Base
{
int additional_;
public:
Derived(const Derived& d)
: Base(d...
Converting Secret Key into a String and Vice Versa
...
You can convert the SecretKey to a byte array (byte[]), then Base64 encode that to a String. To convert back to a SecretKey, Base64 decode the String and use it in a SecretKeySpec to rebuild your original SecretKey.
For Java 8
SecretKey to String:
// create new key
SecretKey secret...
What is the point of a private pure virtual function?
... classes. Methods of derived classes can't call virtual functions from the base class, but they can provide their own implementation for them. According to Herb Sutter, having public non-virtual interface in the base class and a private implementation that can be customized in the derived classes, a...