F# Practice Sets

partial-active-pattern.fs

type Grade = A | B | C | D | E | F | InvalidGrade

let (|MoreThan|_|) grade value = 
    if value > grade then Some MoreThan else None

let (|LessThan|_|) grade value = 
    if value < grade then Some LessThan else None

let (|Between|_|) uppergrade lowergrade value = 
    if uppergrade >= value && value >= lowergrade then Some Between else None

let getGrade grade = 
    match grade with
    | MoreThan 98   -> A
    | Between 98 95 -> B
    | Between 94 90 -> C
    | Between 89 80 -> D
    | Between 79 75 -> E
    | LessThan 75   -> F
    | _ -> InvalidGrade