Most efficient/elegant way to clip a number?

Question

Given a real (n), a maximum value this real can be (upper), and a minimum value this real can be (lower), how can we most efficiently clip n, such that it remains between lo

Answer 1

UPDATE: C++17's header added std::clamp(value, low, high).

In older C++ versions, I'd very rarely go beyond...

return n <= lower ? lower : n >= upper ? upper : n;

...or, if you find it more readable keeping the left-to-right ordering of lower, n and upper...

return n <= lower ? lower : n <= upper ? n : upper;

(using <= lower is better than < lower because when n == lower it avoids having to compare with upper)

If you know you might have them, you'd want to check if NaN / Inf etc. are preserved....

I say rarely and not never just because sometimes less branching can be faster, but you'd sure want to profile it and prove it helped and mattered....