fun findGrade _    []          = "No grade"
  | findGrade name ((n,g)::xs) =
    if name = n then
        g
    else
        findGrade name xs;

fun findGradeBetter _    []          = NONE
  | findGradeBetter name ((n,g)::xs) =
    if name = n then
        SOME g
    else
        findGradeBetter name xs;


fun passingClass name grades =
    case findGradeBetter name grades of
        NONE       => false
      | (SOME "F") => false
      | (SOME "f") => false
      | _          => true;

fun passingClassAlternate name grades =
    case findGradeBetter name grades of
        NONE     => false
      | (SOME g) =>
        if g = "F" orelse g = "f" then
            false
        else
            true;