list($a, $b) = array('str1', 'str2');В pyton, вроде есть что то вроде этого:
a, b = ['str1', 'str2'];А вот в C++ такой языковой конструкции нет. Но это совершенно не проблема, потому что ее можно сделать самому. Вот что у меня получилось
/**
* This is a helper class.
* It can be used only inside the function ListInitializer tolist(Args&& ...args)
* ListInitializer list(Args&& ...args)
* In all other cases, use it not possible
* size is the number of arguments with which the constructor was called
*/
template<typename DataType, unsigned size>
class ListInitializer
{
public:
/**
* Assignment operator
* Ref-qualified forbids such things:
* ListInitializer c(a,b);
* c = arr;
* You can only use this form:
* ListInitializer(a,b) = arr;
* VecType must be convertable to DataType
*/
template<typename ContainerType>
ListInitializer &operator=(ContainerType &&arr) && // <-- Ref-qualified
{
auto it = arr.begin(), itend = arr.end();
unsigned i = 0;
while(it != itend && i < size) {
*parr[i] = *it;
++it;
++i;
}
return *this;
}
/**
* Deleted constructors. Forbids such things:
* tolist q(a,b,c,d,e),w(a,b,c,d,e);
* w = q;
* You can only use this form:
* tolist(a,b,c,d,e) = arr;
*/
ListInitializer(const ListInitializer &that) = delete;
ListInitializer() = delete;
private:
/**
* Constructor with one argument
*/
explicit ListInitializer(DataType& arg) //: size(1)
{
helper(0, arg);
}
/**
* Constructor with a variable (>1) number of arguments
* You can use any number of arguments of type DataType in the constructor.
* tolist(a,b,c,d) = arr;
* tolist(a,b) = arr;
*/
template <typename ...Args>
ListInitializer(DataType& arg0, Args&... args) //: size(sizeof...(Args)+1)
{
helper(0, arg0, args...);
}
/**
* Move constructor
*/
ListInitializer(ListInitializer &&that)
{
for(unsigned i = 0; i < size; i++) {
parr[i] = that.parr[i];
that.parr[i] = nullptr;
}
}
/**
* Helper method.
* Allows to initialize the list of any number of arguments.
* Alternately, one by one makes pointers to the arguments into the internal array.
*/
template <typename ...Args>
void helper(int ind, DataType& arg0, Args&... args)
{
helper(ind, arg0);
helper(++ind, args...);
}
/**
* Helper method.
*/
void helper(int ind, DataType& arg0)
{
parr[ind] = &arg0;
}
template <typename T, typename ...Args>
friend ListInitializer<T, sizeof...(Args)+1> tolist(T& arg0, Args&... args);
// Internal array of pointers to pointers to arguments
DataType* parr[size];
};
template <typename DataType, typename ...Args>
ListInitializer<DataType, sizeof...(Args)+1> tolist(DataType& arg0, Args&... args)
{
return ListInitializer<DataType, sizeof...(Args)+1>(arg0, args...);
}
// Check
#include <iostream>
#include <vector>
int main(){
std::vector<std::string> arr{"str1","str2","str3","str4","str5","str6"};
std::string a,b,c,d,e;
tolist(b) = arr;
std::cout << std::endl << a << " " << b << " " << c << " " << d << " " << e << std::endl;
tolist(a,b,c,d,e) = arr;
std::cout << std::endl << a << " " << b << " " << c << " " << d << " " << e << std::endl;
return 0;
};
/*
* g++ tolist.cpp -std=c++11 && ./a.out
* or
* clang++ tolist.cpp -std=c++11 && ./a.out
*
* |output:
* | str1
* |
* |str1 str2 str3 str4 str5
*
*
*/
Нужен C++11 т.к. используется Ref-qualifiers PS blogger.com как всегда портит код. Надо менять блогодвижок.
