new RObject from Nothing -- create an R NULL object

• Usage:

  RObject null

• Inputs:
• Outputs:
  • a R object, R's NULL;

i1 : RObject null

o1 = NULL

o1 : RObject of type NULL

i2 : (?? RObject null) === null

o2 = true

i3 : RObject null ?? RObject 5

o3 = [1] 5

o3 : RObject of type integer