How to implement the following?

How to implement the following? a and b are selected at random. If the following conditions true it should go inside loop. else again we should wait till those conditions true.

a+b=1  and  

0  <=  a,b  <=  1

Answer 1

[Walter Roberson]

if a + b == 1 && 0 <= a && b <= 1
  %loop goes here
else
  pause(inf);  %"wait until those conditions are true"
end