Question

I have a function: bool inBounds(int value, int low, int high). Is there an STL equivalent that does useful things (takes variables of different types, specifically)? I can’t find one using Google, and I’d prefer to re-use rather than re-write.

Answer 1

In C++17, there’s no direct equivalent of a function like this, but for smaller types with fast equality comparisons you could use std::clamp:

if (val == std::clamp(val, low, high)) {
    ...
}

Alternatively, you can just write your own function to test for this:

template <typename T>
    bool IsInBounds(const T& value, const T& low, const T& high) {
    return !(value < low) && (value < high);
}

This checks if value is in the range [low, high). If you want the range [low, high], you’d write this as

template <typename T>
    bool IsInBounds(const T& value, const T& low, const T& high) {
    return !(value < low) && !(high < value);
}

Note how this is defined purely in terms of operator <, which means that any class that supports just operator < can be used here.

Similarly, here’s one using custom comparators:

template <typename T, typename R, typename Comparator>
    bool IsInBounds(const T& value, const R& low, const R& high, Comparator comp) {
    return !comp(value, low) && comp(value, high);
}

This latter one has the nice advantage that low and high don’t have to be the same type as value, and as long as the comparator can handle that it will work just fine.

Hope this helps!