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fotonmoton's solution

to Grade School in the OCaml Track

Published at Aug 06 2019 · 0 comments
Test suite


This exercise has changed since this solution was written.

Given students' names along with the grade that they are in, create a roster for the school.

In the end, you should be able to:

  • Start with an empty school.
  • Add a student's name to the roster for a grade
    • "Add Jim to grade 2."
    • "OK."
  • Get a list of all students enrolled in a grade
    • "Which students are in grade 2?"
    • "We've only got Jim just now."
  • Get a sorted list of all students in all grades. Grades should sort as 1, 2, 3, etc., and students within a grade should be sorted alphabetically by name.
    • "Who all is enrolled in school right now?"
    • "Grade 1: Anna, Barb, and Charlie. Grade 2: Alex, Peter, and Zoe. Grade 3…"

Note that all our students only have one name. (It's a small town, what do you want?)

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  2. Install OCaml.

  3. For library documentation, follow Useful OCaml resources.

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A pairing session with Phil Battos at gSchool http://gschool.it


open OUnit2
open Grade_school

let assert_lists_equal exp got _ctx =
  let printer = String.concat ";" in
  assert_equal exp got ~printer

let tests = [
  "an empty school has no children in grade 1" >::
  assert_lists_equal [] (grade 1 empty_school);
  "an empty school has Emma in grade 1 after she's been added to grade 1" >::(
    let s = add "Emma" 1 empty_school in
    assert_lists_equal ["Emma"] (grade 1 s)
  "an empty school does not have Emma in grade 1 after she's been added to grade 2" >::(
    let s = add "Emma" 2 empty_school in
    assert_lists_equal [] (grade 1 s)
  "an empty school has Emma, Timmy, Bob and Becky in grade 1 after they've been added to grade 1" >::(
    let s = empty_school |> add "Emma" 1 |> add "Timmy" 1 |> add "Bob" 1 |> add "Becky" 1 in
    assert_lists_equal ["Becky"; "Bob"; "Emma"; "Timmy"] (grade 1 s |> List.sort compare)
  "a sorted school has Emma, Timmy, Bob and Becky in grade 1 in sorted order" >::(
    let s = empty_school |> add "Emma" 1 |> add "Timmy" 1 |> add "Bob" 1 |> add "Becky" 1 |> sorted in
    assert_lists_equal ["Becky"; "Bob"; "Emma"; "Timmy"] (grade 1 s)

let () =
  run_test_tt_main ("grade-school tests" >::: tests)
open Base

module Int_map = Map.M(Int)

type school = string list Int_map.t

let empty_school = Map.empty (module Int)

(* stolen solution from tzemanovic *)
let add name grade school = Map.add_multi ~key:grade ~data:name school

let grade mark school = Map.find_multi school mark

let sorted school = Map.map school ~f:(List.sort ~compare:String.compare)

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