code 41561;
real procedure EXPON (X, LAMBDA);
value X, LAMBDA; real X, LAMBDA;
EXPON:= if LAMBDA ≤ 0
        then STATAL3 ERROR(“EXPON”, 2, LAMBDA)
        else if X ≤ 0 then 0
        else 1 - EXP(-LAMBDA × X);
eop