def is_even(n):
match n:
case 1:
return False
case 0:
return True
# fix No1
case n < 0:
return is_even(-1*n)
case _:
return is_even(n-2)
Python added match/case?! Bunch of mypy issues have been closed too. Maybe its time to dust off some old projects.
It was added in 3.10 and is surprisingly complete. The tutorial pep is a good starting point to see what it can accomplish
My solution in perl back in the day when I was a teenage hobbyist who didn’t know about the modulus operator: Divide by 2 and use regex to check for a decimal point.
if ($num / 2 =~ /\./) { return “odd” }
else { return “even” }
You know, I was going to let this slide under the notion that we’re just ignoring the limited precision of floating point numbers… But then I thought about it and it’s probably not right even if you were computing with real numbers! The decimal representation of real numbers isn’t unique, so this could tell me that “2 = 1.9999…” is odd. Maybe your string coercion is guaranteed to return the finite decimal representation, but I think that would be undecidable.
Ackchyually-- IEEE 754 guarantees any integer with absolute value less than 2^24 to be exactly representable as a single precision float. So, the “divide by 2, check for decimals” should be safe as long as the origin of the number being checked is somewhat reasonable.
This could be optimized by using a recursive function.
You could do this in one line…
By removing all the linebreaks.
Of course there’s an easier way. Just integrate the state of the art API dedicated for this exact problem. https://isevenapi.xyz/