Notes on constexpr in C++.

constexpr.cpp

#include <type_traits>
#include <iostream>
#include <string>

// valid in C++14, but not valid in C++11.
// for statement not allowed in constexpr function in C++11.
constexpr size_t addition(size_t n) {
    size_t s = 0;
    for (size_t i = 0; i <= n; ++i) {
        s += i;
    }
    return s;
}

// if BOUND is 0xffffc, will failed in compile time.
/*
#define BOUND       0xffffb
constexpr int foo(int a) {
    int b = 1;
    for (int k = 0; k < a; k++);
    return b;
}

int t[foo(BOUND)];
*/

// In C++14, constexpr doesn't imply const.
struct non_negative {
    size_t i;
    constexpr size_t const & get() const { return i; }
    size_t & get() { return i; }
};

int main(int, char **) {
    int n;
    scanf("%d", &n);
    addition(n);
    return 0;
}