[gleam] complete strain

gleam/strain/.gitignore

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+*.beam
+*.ez
+build
+erl_crash.dump

gleam/strain/HELP.md

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+# 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/strain.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/strain/README.md

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+# Strain
+
+Welcome to Strain on Exercism's Gleam Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Implement the `keep` and `discard` operation on collections.
+Given a collection and a predicate on the collection's elements, `keep` returns a new collection containing those elements where the predicate is true, while `discard` returns a new collection containing those elements where the predicate is false.
+
+For example, given the collection of numbers:
+
+- 1, 2, 3, 4, 5
+
+And the predicate:
+
+- is the number even?
+
+Then your keep operation should produce:
+
+- 2, 4
+
+While your discard operation should produce:
+
+- 1, 3, 5
+
+Note that the union of keep and discard is all the elements.
+
+The functions may be called `keep` and `discard`, or they may need different names in order to not clash with existing functions or concepts in your language.
+
+## Restrictions
+
+Keep your hands off that filter/reject/whatchamacallit functionality provided by your standard library!
+Solve this one yourself using other basic tools instead.
+
+## Source
+
+### Created by
+
+- @natanaelsirqueira
+
+### Based on
+
+Conversation with James Edward Gray II - http://graysoftinc.com/

gleam/strain/gleam.toml

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+name = "strain"
+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/strain/manifest.toml

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+# This file was generated by Gleam
+# You typically do not need to edit this file
+
+packages = [
+  { name = "argv", version = "1.0.1", build_tools = ["gleam"], requirements = [], otp_app = "argv", source = "hex", outer_checksum = "A6E9009E50BBE863EB37D963E4315398D41A3D87D0075480FC244125808F964A" },
+  { name = "exercism_test_runner", version = "1.7.0", 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 = "2FC1BADB19BEC2AE77BFD2D3A606A014C85412A7B874CAFC4BA8CF04B0B257CD" },
+  { name = "gap", version = "1.1.0", build_tools = ["gleam"], requirements = ["gleam_community_ansi", "gleam_stdlib"], otp_app = "gap", source = "hex", outer_checksum = "2EE1B0A17E85CF73A0C1D29DA315A2699117A8F549C8E8D89FA8261BE41EDEB1" },
+  { name = "glance", version = "0.8.2", build_tools = ["gleam"], requirements = ["gleam_stdlib", "glexer"], otp_app = "glance", source = "hex", outer_checksum = "ACF09457E8B564AD7A0D823DAFDD326F58263C01ACB0D432A9BEFDEDD1DA8E73" },
+  { 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 = "1.3.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_community_colour", source = "hex", outer_checksum = "A49A5E3AE8B637A5ACBA80ECB9B1AFE89FD3D5351FF6410A42B84F666D40D7D5" },
+  { 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 = "1.0.0", build_tools = ["gleam"], requirements = ["gleam_stdlib", "thoas"], otp_app = "gleam_json", source = "hex", outer_checksum = "8B197DD5D578EA6AC2C0D4BDC634C71A5BCA8E7DB5F47091C263ECB411A60DF3" },
+  { 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 = "0.36.0", build_tools = ["gleam"], requirements = [], otp_app = "gleam_stdlib", source = "hex", outer_checksum = "C0D14D807FEC6F8A08A7C9EF8DFDE6AE5C10E40E21325B2B29365965D82EB3D4" },
+  { name = "glexer", version = "0.7.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "glexer", source = "hex", outer_checksum = "4484942A465482A0A100936E1E5F12314DB4B5AC0D87575A7B9E9062090B96BE" },
+  { name = "simplifile", version = "1.5.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "simplifile", source = "hex", outer_checksum = "EB9AA8E65E5C1E3E0FDCFC81BC363FD433CB122D7D062750FFDF24DE4AC40116" },
+  { name = "thoas", version = "0.4.1", build_tools = ["rebar3"], requirements = [], otp_app = "thoas", source = "hex", outer_checksum = "4918D50026C073C4AB1388437132C77A6F6F7C8AC43C60C13758CC0ADCE2134E" },
+]
+
+[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/strain/src/strain.gleam

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+pub fn keep(list: List(t), predicate: fn(t) -> Bool) -> List(t) {
+  case list {
+    [] -> []
+    [head, ..tail] -> {
+      case predicate(head) {
+        True -> [head, ..keep(tail, predicate)]
+        False -> keep(tail, predicate)
+      }
+    }
+  }
+}
+
+pub fn discard(list: List(t), predicate: fn(t) -> Bool) -> List(t) {
+  keep(list, fn(t) { !predicate(t) })
+}

gleam/strain/test/strain_test.gleam

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+import exercism/test_runner
+import gleam/int
+import gleam/list
+import gleam/string
+import strain
+
+pub fn main() {
+  test_runner.main()
+}
+
+pub fn keep_on_empty_list_returns_empty_list_test() {
+  let assert [] = strain.keep([], fn(_) { True })
+}
+
+pub fn keeps_everything_test() {
+  let assert [1, 2, 3] = strain.keep([1, 2, 3], fn(_) { True })
+}
+
+pub fn keeps_nothing_test() {
+  let assert [] = strain.keep([1, 2, 3], fn(_) { False })
+}
+
+pub fn keeps_first_and_last_test() {
+  let assert [1, 3] = strain.keep([1, 2, 3], int.is_odd)
+}
+
+pub fn keeps_neither_first_nor_last_test() {
+  let assert [2] = strain.keep([1, 2, 3], int.is_even)
+}
+
+pub fn keeps_strings_starting_with_z_test() {
+  let assert ["zebra", "zombies", "zelot"] =
+    strain.keep(
+      ["apple", "zebra", "banana", "zombies", "cherimoya", "zelot"],
+      fn(word) { string.starts_with(word, "z") },
+    )
+}
+
+pub fn keeps_lists_containing_the_number_5_test() {
+  let list = [
+    [1, 2, 3],
+    [5, 5, 5],
+    [5, 1, 2],
+    [2, 1, 2],
+    [1, 5, 2],
+    [2, 2, 1],
+    [1, 2, 5],
+  ]
+
+  let assert [[5, 5, 5], [5, 1, 2], [1, 5, 2], [1, 2, 5]] =
+    strain.keep(list, fn(row) { list.any(row, fn(n) { n == 5 }) })
+}
+
+pub fn discard_on_empty_list_returns_empty_list_test() {
+  let assert [] = strain.discard([], fn(_) { True })
+}
+
+pub fn discards_everything_test() {
+  let assert [] = strain.discard([1, 2, 3], fn(_) { True })
+}
+
+pub fn discards_nothing_test() {
+  let assert [1, 2, 3] = strain.discard([1, 2, 3], fn(_) { False })
+}
+
+pub fn discards_first_and_last_test() {
+  let assert [2] = strain.discard([1, 2, 3], int.is_odd)
+}
+
+pub fn discards_neither_first_nor_last_test() {
+  let assert [1, 3] = strain.discard([1, 2, 3], int.is_even)
+}
+
+pub fn discards_strings_starting_with_z_test() {
+  let assert ["apple", "banana", "cherimoya"] =
+    strain.discard(
+      ["apple", "zebra", "banana", "zombies", "cherimoya", "zelot"],
+      fn(word) { string.starts_with(word, "z") },
+    )
+}
+
+pub fn discards_lists_containing_the_number_5_test() {
+  let list = [
+    [1, 2, 3],
+    [5, 5, 5],
+    [5, 1, 2],
+    [2, 1, 2],
+    [1, 5, 2],
+    [2, 2, 1],
+    [1, 2, 5],
+  ]
+
+  let assert [[1, 2, 3], [2, 1, 2], [2, 2, 1]] =
+    strain.discard(list, fn(row) { list.any(row, fn(n) { n == 5 }) })
+}