[gleam] complete book-store

gleam/book-store/.gitignore

@@ -0,0 +1,4 @@
+*.beam
+*.ez
+build
+erl_crash.dump

gleam/book-store/HELP.md

@@ -0,0 +1,32 @@
+# Help
+
+## Running the tests
+
+To run the tests, run the command `gleam test` from within the exercise directory.
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit src/book_store.gleam` command.
+This command will upload your solution to the Exercism website and print the solution page's URL.
+
+It's possible to submit an incomplete solution which allows you to:
+
+- See how others have completed the exercise
+- Request help from a mentor
+
+## Need to get help?
+
+If you'd like help solving the exercise, check the following pages:
+
+- The [Gleam track's documentation](https://exercism.org/docs/tracks/gleam)
+- The [Gleam track's programming category on the forum](https://forum.exercism.org/c/programming/gleam)
+- [Exercism's programming category on the forum](https://forum.exercism.org/c/programming/5)
+- The [Frequently Asked Questions](https://exercism.org/docs/using/faqs)
+
+Should those resources not suffice, you could submit your (incomplete) solution to request mentoring.
+
+To get help if you're having trouble, you can use one of the following resources:
+
+- [gleam.run](https://gleam.run/documentation/) is the gleam official documentation.
+- [Discord](https://discord.gg/Fm8Pwmy) is the discord channel.
+- [StackOverflow](https://stackoverflow.com/questions/tagged/gleam) can be used to search for your problem and see if it has been answered already. You can also ask and answer questions.

gleam/book-store/README.md

@@ -0,0 +1,76 @@
+# Book Store
+
+Welcome to Book Store on Exercism's Gleam Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+To try and encourage more sales of different books from a popular 5 book series, a bookshop has decided to offer discounts on multiple book purchases.
+
+One copy of any of the five books costs $8.
+
+If, however, you buy two different books, you get a 5% discount on those two books.
+
+If you buy 3 different books, you get a 10% discount.
+
+If you buy 4 different books, you get a 20% discount.
+
+If you buy all 5, you get a 25% discount.
+
+Note that if you buy four books, of which 3 are different titles, you get a 10% discount on the 3 that form part of a set, but the fourth book still costs $8.
+
+Your mission is to write code to calculate the price of any conceivable shopping basket (containing only books of the same series), giving as big a discount as possible.
+
+For example, how much does this basket of books cost?
+
+- 2 copies of the first book
+- 2 copies of the second book
+- 2 copies of the third book
+- 1 copy of the fourth book
+- 1 copy of the fifth book
+
+One way of grouping these 8 books is:
+
+- 1 group of 5 (1st, 2nd,3rd, 4th, 5th)
+- 1 group of 3 (1st, 2nd, 3rd)
+
+This would give a total of:
+
+- 5 books at a 25% discount
+- 3 books at a 10% discount
+
+Resulting in:
+
+- 5 × (100% - 25%) × $8 = 5 × $6.00 = $30.00, plus
+- 3 × (100% - 10%) × $8 = 3 × $7.20 = $21.60
+
+Which equals $51.60.
+
+However, a different way to group these 8 books is:
+
+- 1 group of 4 books (1st, 2nd, 3rd, 4th)
+- 1 group of 4 books (1st, 2nd, 3rd, 5th)
+
+This would give a total of:
+
+- 4 books at a 20% discount
+- 4 books at a 20% discount
+
+Resulting in:
+
+- 4 × (100% - 20%) × $8 = 4 × $6.40 = $25.60, plus
+- 4 × (100% - 20%) × $8 = 4 × $6.40 = $25.60
+
+Which equals $51.20.
+
+And $51.20 is the price with the biggest discount.
+
+## Source
+
+### Created by
+
+- @massivefermion
+
+### Based on
+
+Inspired by the harry potter kata from Cyber-Dojo. - https://cyber-dojo.org

gleam/book-store/gleam.toml

@@ -0,0 +1,12 @@
+name = "book_store"
+version = "0.1.0"
+
+[dependencies]
+gleam_bitwise = "~> 1.2"
+gleam_otp = "~> 0.7 or ~> 1.0"
+gleam_stdlib = "~> 0.32 or ~> 1.0"
+simplifile = "~> 1.0"
+gleam_erlang = ">= 0.25.0 and < 1.0.0"
+
+[dev-dependencies]
+exercism_test_runner = "~> 1.4"

gleam/book-store/manifest.toml

@@ -0,0 +1,28 @@
+# This file was generated by Gleam
+# You typically do not need to edit this file
+
+packages = [
+  { name = "argv", version = "1.0.2", build_tools = ["gleam"], requirements = [], otp_app = "argv", source = "hex", outer_checksum = "BA1FF0929525DEBA1CE67256E5ADF77A7CDDFE729E3E3F57A5BDCAA031DED09D" },
+  { name = "exercism_test_runner", version = "1.8.0", build_tools = ["gleam"], requirements = ["argv", "gap", "glance", "gleam_community_ansi", "gleam_erlang", "gleam_json", "gleam_stdlib", "simplifile"], otp_app = "exercism_test_runner", source = "hex", outer_checksum = "B944D89A9D049897DF28C63D595D89CB54D8C407D06EFFCE4CDA8C3EC1C9F51E" },
+  { name = "filepath", version = "1.0.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "filepath", source = "hex", outer_checksum = "EFB6FF65C98B2A16378ABC3EE2B14124168C0CE5201553DE652E2644DCFDB594" },
+  { name = "gap", version = "1.1.3", build_tools = ["gleam"], requirements = ["gleam_community_ansi", "gleam_stdlib"], otp_app = "gap", source = "hex", outer_checksum = "6EF5E3B523FDFBC317E9EA28D5163EE04744A97C007106F90207569789612291" },
+  { name = "glance", version = "0.11.0", build_tools = ["gleam"], requirements = ["gleam_stdlib", "glexer"], otp_app = "glance", source = "hex", outer_checksum = "8F3314D27773B7C3B9FB58D8C02C634290422CE531988C0394FA0DF8676B964D" },
+  { name = "gleam_bitwise", version = "1.3.1", build_tools = ["gleam"], requirements = [], otp_app = "gleam_bitwise", source = "hex", outer_checksum = "B36E1D3188D7F594C7FD4F43D0D2CE17561DE896202017548578B16FE1FE9EFC" },
+  { name = "gleam_community_ansi", version = "1.4.0", build_tools = ["gleam"], requirements = ["gleam_community_colour", "gleam_stdlib"], otp_app = "gleam_community_ansi", source = "hex", outer_checksum = "FE79E08BF97009729259B6357EC058315B6FBB916FAD1C2FF9355115FEB0D3A4" },
+  { name = "gleam_community_colour", version = "1.4.0", build_tools = ["gleam"], requirements = ["gleam_json", "gleam_stdlib"], otp_app = "gleam_community_colour", source = "hex", outer_checksum = "795964217EBEDB3DA656F5EB8F67D7AD22872EB95182042D3E7AFEF32D3FD2FE" },
+  { name = "gleam_erlang", version = "0.25.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_erlang", source = "hex", outer_checksum = "054D571A7092D2A9727B3E5D183B7507DAB0DA41556EC9133606F09C15497373" },
+  { name = "gleam_json", version = "1.0.1", build_tools = ["gleam"], requirements = ["gleam_stdlib", "thoas"], otp_app = "gleam_json", source = "hex", outer_checksum = "9063D14D25406326C0255BDA0021541E797D8A7A12573D849462CAFED459F6EB" },
+  { name = "gleam_otp", version = "0.10.0", build_tools = ["gleam"], requirements = ["gleam_erlang", "gleam_stdlib"], otp_app = "gleam_otp", source = "hex", outer_checksum = "0B04FE915ACECE539B317F9652CAADBBC0F000184D586AAAF2D94C100945D72B" },
+  { name = "gleam_stdlib", version = "0.39.0", build_tools = ["gleam"], requirements = [], otp_app = "gleam_stdlib", source = "hex", outer_checksum = "2D7DE885A6EA7F1D5015D1698920C9BAF7241102836CE0C3837A4F160128A9C4" },
+  { name = "glexer", version = "1.0.1", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "glexer", source = "hex", outer_checksum = "BD477AD657C2B637FEF75F2405FAEFFA533F277A74EF1A5E17B55B1178C228FB" },
+  { name = "simplifile", version = "1.7.0", build_tools = ["gleam"], requirements = ["filepath", "gleam_stdlib"], otp_app = "simplifile", source = "hex", outer_checksum = "1D5DFA3A2F9319EC85825F6ED88B8E449F381B0D55A62F5E61424E748E7DDEB0" },
+  { name = "thoas", version = "1.2.1", build_tools = ["rebar3"], requirements = [], otp_app = "thoas", source = "hex", outer_checksum = "E38697EDFFD6E91BD12CEA41B155115282630075C2A727E7A6B2947F5408B86A" },
+]
+
+[requirements]
+exercism_test_runner = { version = "~> 1.4" }
+gleam_bitwise = { version = "~> 1.2" }
+gleam_erlang = { version = ">= 0.25.0 and < 1.0.0" }
+gleam_otp = { version = "~> 0.7 or ~> 1.0" }
+gleam_stdlib = { version = "~> 0.32 or ~> 1.0" }
+simplifile = { version = "~> 1.0" }

gleam/book-store/src/book_store.gleam

@@ -0,0 +1,32 @@
+import gleam/dict
+import gleam/float
+import gleam/int
+import gleam/list
+
+pub fn lowest_price(books: List(Int)) -> Float {
+  books
+  |> list.group(fn(n) { n })
+  |> dict.values
+  |> list.map(list.length)
+  |> price(0.0)
+}
+
+fn price(books: List(Int), sum: Float) -> Float {
+  let books =
+    list.filter(books, fn(b) { b > 0 })
+    |> list.sort(int.compare)
+    |> list.map(int.subtract(_, 1))
+
+  case books {
+    [a] -> sum +. int.to_float(a + 1) *. 800.0
+    [_, _] -> price(books, sum +. 2.0 *. 760.0)
+    [_, _, _] -> price(books, sum +. 3.0 *. 720.0)
+    [_, _, _, _] -> price(books, sum +. 4.0 *. 640.0)
+    [a, ..rest] ->
+      float.min(
+        price([a + 1, ..rest], sum +. 4.0 *. 640.0),
+        price([a, ..rest], sum +. 5.0 *. 600.0),
+      )
+    _ -> sum
+  }
+}

gleam/book-store/test/book_store_test.gleam

@@ -0,0 +1,151 @@
+import book_store
+import exercism/should
+import exercism/test_runner
+
+pub fn main() {
+  test_runner.main()
+}
+
+pub fn only_a_single_book_test() {
+  let input = [1]
+  let output = book_store.lowest_price(input)
+  let expected = 800.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn two_of_the_same_book_test() {
+  let input = [2, 2]
+  let output = book_store.lowest_price(input)
+  let expected = 1600.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn empty_basket_test() {
+  let input = []
+  let output = book_store.lowest_price(input)
+  let expected = 0.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn two_different_books_test() {
+  let input = [1, 2]
+  let output = book_store.lowest_price(input)
+  let expected = 1520.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn three_different_books_test() {
+  let input = [1, 2, 3]
+  let output = book_store.lowest_price(input)
+  let expected = 2160.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn four_different_books_test() {
+  let input = [1, 2, 3, 4]
+  let output = book_store.lowest_price(input)
+  let expected = 2560.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn five_different_books_test() {
+  let input = [1, 2, 3, 4, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 3000.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn two_groups_of_four_is_cheaper_than_group_of_five_plus_group_of_three_test() {
+  let input = [1, 1, 2, 2, 3, 3, 4, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 5120.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn two_groups_of_four_is_cheaper_than_groups_of_five_and_three_test() {
+  let input = [1, 1, 2, 3, 4, 4, 5, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 5120.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn group_of_four_plus_group_of_two_is_cheaper_than_two_groups_of_three_test() {
+  let input = [1, 1, 2, 2, 3, 4]
+  let output = book_store.lowest_price(input)
+  let expected = 4080.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn two_each_of_first_four_books_and_one_copy_each_of_rest_test() {
+  let input = [1, 1, 2, 2, 3, 3, 4, 4, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 5560.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn two_copies_of_each_book_test() {
+  let input = [1, 1, 2, 2, 3, 3, 4, 4, 5, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 6000.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn three_copies_of_first_book_and_two_each_of_remaining_test() {
+  let input = [1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 1]
+  let output = book_store.lowest_price(input)
+  let expected = 6800.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn three_each_of_first_two_books_and_two_each_of_remaining_books_test() {
+  let input = [1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 1, 2]
+  let output = book_store.lowest_price(input)
+  let expected = 7520.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn four_groups_of_four_are_cheaper_than_two_groups_each_of_five_and_three_test() {
+  let input = [1, 1, 2, 2, 3, 3, 4, 5, 1, 1, 2, 2, 3, 3, 4, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 10_240.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn check_that_groups_of_four_are_created_properly_even_when_there_are_more_groups_of_three_than_groups_of_five_test() {
+  let input = [1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 5, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 14_560.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn one_group_of_one_and_four_is_cheaper_than_one_group_of_two_and_three_test() {
+  let input = [1, 1, 2, 3, 4]
+  let output = book_store.lowest_price(input)
+  let expected = 3360.0
+  output
+  |> should.equal(expected)
+}
+
+pub fn one_group_of_one_and_two_plus_three_groups_of_four_is_cheaper_than_one_group_of_each_size_test() {
+  let input = [1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5]
+  let output = book_store.lowest_price(input)
+  let expected = 10_000.0
+  output
+  |> should.equal(expected)
+}