### 5.39.4 Ranges of values defined by their center : center2interval

center2interval takes as argument a vector V of reals and optionally a real as second argument (by default V[0]-(V[1]-V[0])/2).
center2interval returns a vector of ranges of values having the real values of the first argument as centers, where the value of the second argument is the left boundary of the first range.
Input :

center2interval([3,5,8])

Or (since the default value is 3-(5-3)/2=2) :

center2interval([3,5,8],2)

Output :

[2..4,4..6,6..10]

Input :

center2interval([3,5,8],2.5)

Output :

[2.5..3.5,3.5..6.5,6.5..9.5]