lucab0ni - 9 months ago 53

C++ Question

Let's say I have an array of integers defined like that:

`static const int IntArray[] = {1, 5, 10, 12, 17};`

Is there a way to the minimum or maximum value at compile time?

Thanks to the comments to the answer it was me clear that the array has to be declared

`constexpr`

`const`

`static constexpr int IntArray[] = {1, 5, 10, 12, 17};`

Answer Source

Note: this answer assumes that the array is actually `constexpr`

-- if it is only `const`

, its contents are *not* compile-time constants, and thus it is not possible at all.

Let's get the C++17 solution out of the way for future search-landers:

```
constexpr int IntArray[] = {1, 5, 10, 12, 17};
constexpr int min = *std::min_element(std::begin(IntArray), std::end(IntArray));
static_assert(min == 1);
```

C++11 is more picky with `constexpr`

functions, so we have to roll out a recursive algorithm. This one is a simple, linear one:

```
template <class T>
constexpr T &constexpr_min(T &a, T &b) {
return a > b ? b : a;
}
template <class T>
constexpr T &arrayMin_impl(T *begin, T *end) {
return begin + 1 == end
? *begin
: constexpr_min(*begin, arrayMin_impl(begin + 1, end));
}
template <class T, std::size_t N>
constexpr T &arrayMin(T(&arr)[N]) {
return arrayMin_impl(arr, arr + N);
}
constexpr int IntArray[] = {1, 5, 10, 12, 17};
constexpr int min = arrayMin(IntArray);
```