On Sun, Jul 31, 2016 at 09:38:44PM +0200, Victor Stinner wrote:
I dislike this API. What's the point of calling clamp(x)? clamp(b, a) is min(a, b) and clamp(a, max_val=b) is just max(a, b).
You have that the wrong way around. If you supply a lower-bounds, you must take the max(), not the min(). If you supply a upper-bounds, you take the min(), not the max(). It's easy to get wrong.
My point is that all parameters must be mandatory.
I don't care too much whether the parameters are mandatory or have defaults, so long as it is *possible* to pass something for the lower and upper bounds which mean "unbounded". There are four obvious alternatives (well three obvious ones and one surprising one):
(1) Explicitly pass -INFINITY or +INFINITY as needed; but which infinity, float or Decimal? If you pass the wrong one, you may have to pay the cost of converting your values to float/Decimal, which could end up expensive if you have a lot of them.
(2) Pass a NAN as the bounds. With my implementation, that actually works! But it's a surprising accident of implementation, it feels wrong and looks weird, and again, it may require converting the values to float/Decimal.
(3) Use some special Infimum and Supremum objects which are smaller than, and greater than, every other value. But we don't have such objects, so you'd need to create your own.
(4) Use None as a placeholder for "no limit". That's my preferred option.
Of course, even if None is accepted as "no limit", the caller can still explicitly provide an infinity if they prefer.
As I said, I don't particularly care whether the lower and upper bounds have default values. But I think it is useful and elegant to accept None (as well as infinity) to mean "no limit".