grade_report.fsx in F#

Report cards from a record roster, a guarded match, and printf columns.

// Average each student's scores and print a letter-grade report card.

type Student = { Name: string; Scores: int list }

let roster =
    [ { Name = "Ada"; Scores = [92; 88; 97] }
      { Name = "Grace"; Scores = [84; 91; 78] }
      { Name = "Alan"; Scores = [70; 66; 74] }
      { Name = "Edsger"; Scores = [58; 67; 61] } ]

let average student =
    student.Scores |> List.sumBy float
    |> fun total -> total / float (List.length student.Scores)

let letter avg =
    match avg with
    | a when a >= 90.0 -> "A"
    | a when a >= 80.0 -> "B"
    | a when a >= 70.0 -> "C"
    | a when a >= 60.0 -> "D"
    | _ -> "F"

printfn "student  avg grade"
for s in roster |> List.sortBy (fun s -> s.Name) do
    let avg = average s
    printfn "%-8s %4.1f  %s" s.Name avg (letter avg)

let classAvg =
    roster |> List.collect (fun s -> s.Scores)
    |> List.averageBy float
printfn "Class average: %.1f" classAvg

How it works

Student is a record; the roster is a list literal.
letter grades through a ladder of when guards.
List.collect pools every score for the class average.

Keywords and builtins used here

Student
do
float
for
fun
in
let
list
match
string
type
when
with

The run, in numbers

Lines: 31
Characters to type: 843
Tokens: 248
Three-star pace: 60 tpm

At the three-star pace of 60 tokens a minute, this run takes about 248 seconds.

Type this snippet

Step 2 of 3 in Encore, step 26 of 27 in Language basics.

← Previous Next →