Intervals
Key Intervals in Multi Linear 1D Fn refers to an array of intervals expressed as a 1D-array of objects of type Real Interval
This entry is generally mandatory, but becomes optional in the case of a single linear segment, i.e. when only one slope is defined through Slopes
In the latter case, if the entry here is missing, one single interval is assumed that equals the whole real axis and represented by the object (,)