Generates a constant number.
Constant(g,a)
Always generates the same number, equal to the parameter a.
Constant(g,1) =
(1,g)
for i in 1:5 loop
  (u[i],g) := Constant(g,3);
end for;
// u = {3,3,3,3,3};
function Constant extends Var; end Constant;