code 35116;
 real procedure ARCTANH(X); value X; real X;
 if ABS(X) >= 1 then 
 begin 
     ARCTANH:= SIGN(X)*GIANT
 end else 
 begin real AX;
     AX:= ABS(X); ARCTANH:= SIGN(X)*.5*LOG ONE PLUS X(2*AX/(1-AX))
 end ARCTANH;
        eop