Is there a term for this subtraction formula?

Question

Is there a term for this concept? Any link?

n is a decimal from 0 to 1, including

FORMULA

n = 0.5
x = 1 - n

EXAMPLES

1.0 => 0.0
0.8 => 0.2
0.5 => 0.5
0.3 => 0.7
0.0 => 1.0

I have this use case all the time and would like a term for it.

Answer 1

The map $\,x\mapsto 1-x\,$ is known as the reflection (or inversion) of $\,x$ across the point $\,1/2,\,$ see for example the Wikipedia page on point reflections. If we shift $\,1/2\,$ to the origin by changing variables $\ x = z+1/2\ $ then it is simply the reflection through $\,0,\,$ i.e. $\,z\mapsto -z,\,$ i.e. negation.