Result is +Number
    which should be preferred for portability.
Result is identical to Number.
In coroutining mode, if Number is uninstantiated, the call to +/2 is delayed until this variable is instantiated.
Success:
    Result is + 1.		% gives Result = 1
    Result is + 5.        	% gives Result = 5
    Result is + -6.2.     	% gives Result = -6.2
    Result is +(1).		% gives Result = 1
    Result is +(5).        	% gives Result = 5
    Result is +(-6.2).     	% gives Result = -6.2