null

null -- a symbol that represents the presence of nothing.

Printing it causes nothing to appear. When it is the value of an expression entered into the interpreter, the output line doesn't appear. Empty spots in a list are represented by it.

It is the only member of the class Nothing.

     i1 = x = {2,3,,4}
     
     o1 = {2,3,null,4}
     
     o1 : List

     i2 = x#2

     i3 = name x#2
     
     o3 = "null"