Is there some metric for computing similarity between two numbers which takes values in the interval $[0, 1]$?
I want something like:
$sim(1,1) = 1$
$sim(1,2) = 0.5$
$sim(50,47) = 0.78$
$sim(100,99) = 0.99$
If two numbers are small, then similarity is sensitive. But, if two numbers are big, then similarity is less sensitive.
Is there some metric like that?