madsflensted's solution

to Grade School in the OCaml Track

Published at Jan 11 2019 · 0 comments
Instructions
Test suite
Solution

Note:

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?)

Getting Started

For installation and learning resources, refer to the exercism help page.

Installation

To work on the exercises, you will need `Opam` and `Base`. Consult opam website for instructions on how to install `opam` for your OS. Once `opam` is installed open a terminal window and run the following command to install base:

``````opam install base
``````

To run the tests you will need `OUnit`. Install it using `opam`:

``````opam install ounit
``````

Running Tests

A Makefile is provided with a default target to compile your solution and run the tests. At the command line, type:

``````make
``````

Interactive Shell

`utop` is a command line program which allows you to run Ocaml code interactively. The easiest way to install it is via opam:

``````opam install utop
``````

Consult utop for more detail.

Feedback, Issues, Pull Requests

The exercism/ocaml repository on GitHub is the home for all of the Ocaml exercises.

If you have feedback about an exercise, or want to help implementing a new one, head over there and create an issue. We'll do our best to help you!

Source

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

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

test.ml

``````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

(** Grade-school exercise *)
type school = string list Map.M(Int).t

let empty_school =
Map.empty (module Int)

(** Add a student to a school *)
let add name grade school =
let students =
match Map.find school grade with
| Some names -> (name :: names) |> List.sort ~compare:String.compare
| None -> name :: []
in
Map.set school ~key:grade ~data:students

(** Get all the students from a grade *)
let grade g school =
match Map.find school g with
| Some students -> students
| None -> []

(** Sort the list of students in a grade, if necessary *)
let sorted school =
school``````

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