I do not agree clamp should be restricted to numeric values. I would expect
clamp to be agnostic to the specifics of floats/numbers and like sort
expect it to work for any values as long as they compare (using a dunder).
I think having something like min=-math.inf is hence right out in my mind.
If I got this right, the implementation could be as simple as:
def clamp(value, *, min=None, max=None):
if min is not None and value < min:
return min
if max is not None and max < value:
return max
return value
I think the crucial question here is: does the order of the ifs matter and
is that an issue. The only time (barring side effects, values changing in
between calls et cetera) it would make a difference if max < value < min.
Assuming transitivity (can anybody come up with an example of a
non-transitive order where clamping makes sense?) this means max < min and
so you can work around this by disallowing it:
def clamp_safe(value, * min=None, max=None):
if max < min:
raise SomeException("Something about min < max")
return clamp(value, min=min, max=max)
What I like about both of these is that they only use "<", just like sort.
Going back to nans, I think that would mean:
clamp(nan, min, max) = nan
clamp(value, nan, max) = clamp(value, None, max) = max(value, max)
clamp(value, min, nan) = clamp(value, min, None) = min(value, min)
On Mon, 6 Jul 2020 at 02:55, Christopher Barker <[email protected]> wrote:
>
> and we can use +inf and -inf for unlimited bounds as well. Yes, they are a
> bit of a pain to write in Python, but we could do:
>
> def clamp(value, min=-math.inf, max=math.inf):
> ...
>
> yes, that would make them optional, rather than required, and therefore
> provide a slight asymmetry between specifying min only or max only, but
> still be handy. to make it more consistent, but maybe more annoying in the
> common case, we could make them keyword only.
>
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