### 5.35.4 Intervals 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 intervals having the real values of the first argument as centers, where the value of the second argument is the left boundary of the first interval.
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]