datatype result = Neg | Zero | Pos
table t : {A : int}
fun main () : transaction page =
let
fun check () =
r <- oneRow (SELECT SUM(t.A) AS X FROM t);
return (if r.X < 0 then
Neg
else if r.X = 0 then
Zero
else
Pos)
fun show r =
case r of
Neg => -
| Zero => 0
| Pos => +
in
s <- source Zero;
return