A constexpr example in C++14 with custom object initialization. #c++ #constexpr

constexpr-object-example.cpp

#include <iostream>

using namespace std;

constexpr int get_magic_number(int x)
{
    return x + 1999;
}

template <int N>
class foo
{
public:

    static constexpr const int magic_number = get_magic_number(0);

private: 
    int seq[N];

    int val;

public:

    constexpr foo(int v): seq(), val(v)
    {
        for (int i = 0; i < N; ++i)
            seq[i] = i + 1;
    }

    void print() const
    {
        cerr << "foo(" << val << ")" << endl;
    }

    int at(int i) const { return seq[i]; }
    
    static constexpr const foo<N> foo1 = foo<N>(1);
};

int main()
{

    cerr << "magic-number: " << foo<1000>::magic_number << endl;
    
    foo<1000> foo1 = foo<1000>::foo1;

    foo1.print();

    cerr << "foo1.at(150) = " << foo1.at(150) << endl;

    return 0;
}