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add strain (exercism#206)
* Add strain
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‎config.json

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"prerequisites": [],
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"difficulty": 1
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},
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{
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"slug": "strain",
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"name": "Strain",
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"uuid": "af541ed6-4112-4b61-99dd-fd29424ae859",
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"practices": [],
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"prerequisites": [],
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"difficulty": 1
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},
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{
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"slug": "high-scores",
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"name": "High Scores",

‎exercises/practice/strain/.docs/instructions.append.md

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# Instructions append
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## Implementaton Notes
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The test suite passes a Function class instance to the `keep` and `discard` methods as a [block argument][block-argument].
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To successfully pass the tests, you'll need to call that function inside your code.
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If you're unfamiliar with how to do this, please consult the [Function class documentation][function-class].
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[block-argument]: https://wren.io/functions.html#block-arguments
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[function-class]: https://wren.io/modules/core/fn.html

‎exercises/practice/strain/.docs/instructions.md

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# Instructions
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Implement the `keep` and `discard` operation on collections.
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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.
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For example, given the collection of numbers:
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- 1, 2, 3, 4, 5
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And the predicate:
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- is the number even?
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Then your keep operation should produce:
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- 2, 4
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While your discard operation should produce:
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- 1, 3, 5
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Note that the union of keep and discard is all the elements.
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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.
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## Restrictions
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Keep your hands off that filter/reject/whatchamacallit functionality provided by your standard library!
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Solve this one yourself using other basic tools instead.

‎exercises/practice/strain/.meta/config.json

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{
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"authors": [
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"BNAndras"
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],
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"files": {
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"solution": [
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"strain.wren"
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],
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"test": [
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"strain.spec.wren"
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],
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"example": [
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".meta/proof.ci.wren"
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]
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},
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"blurb": "Implement the `keep` and `discard` operation on collections.",
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"source": "Conversation with James Edward Gray II",
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"source_url": "http://graysoftinc.com/"
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}

‎exercises/practice/strain/.meta/proof.ci.wren

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class Strain {
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static keep(list, predicate) {
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var kept = []
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for (item in list) {
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if (predicate.call(item)) {
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kept.add(item)
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}
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}
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return kept
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}
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static discard(list, predicate) {
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return keep(list) { |x| !predicate.call(x) }
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}
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}
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‎exercises/practice/strain/.meta/tests.toml

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# This is an auto-generated file.
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#
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# Regenerating this file via `configlet sync` will:
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# - Recreate every `description` key/value pair
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# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
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# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
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# - Preserve any other key/value pair
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#
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# As user-added comments (using the # character) will be removed when this file
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# is regenerated, comments can be added via a `comment` key.
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[26af8c32-ba6a-4eb3-aa0a-ebd8f136e003]
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description = "keep on empty list returns empty list"
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[f535cb4d-e99b-472a-bd52-9fa0ffccf454]
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description = "keeps everything"
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[950b8e8e-f628-42a8-85e2-9b30f09cde38]
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description = "keeps nothing"
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[92694259-6e76-470c-af87-156bdf75018a]
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description = "keeps first and last"
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[938f7867-bfc7-449e-a21b-7b00cbb56994]
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description = "keeps neither first nor last"
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[8908e351-4437-4d2b-a0f7-770811e48816]
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description = "keeps strings"
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[2728036b-102a-4f1e-a3ef-eac6160d876a]
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description = "keeps lists"
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[ef16beb9-8d84-451a-996a-14e80607fce6]
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description = "discard on empty list returns empty list"
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[2f42f9bc-8e06-4afe-a222-051b5d8cd12a]
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description = "discards everything"
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[ca990fdd-08c2-4f95-aa50-e0f5e1d6802b]
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description = "discards nothing"
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[71595dae-d283-48ca-a52b-45fa96819d2f]
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description = "discards first and last"
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[ae141f79-f86d-4567-b407-919eaca0f3dd]
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description = "discards neither first nor last"
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[daf25b36-a59f-4f29-bcfe-302eb4e43609]
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description = "discards strings"
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[a38d03f9-95ad-4459-80d1-48e937e4acaf]
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description = "discards lists"

‎exercises/practice/strain/LICENSE

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MIT License
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Copyright (c) 2022 Exercism
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.

‎exercises/practice/strain/package.wren

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import "wren-package" for WrenPackage, Dependency
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import "os" for Process
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class Package is WrenPackage {
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construct new() {}
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name { "exercism/strain" }
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dependencies {
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return [
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Dependency.new("wren-testie", "0.3.0", "https://github.com/joshgoebel/wren-testie.git")
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]
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}
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}
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Package.new().default()

‎exercises/practice/strain/strain.spec.wren

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import "wren-testie/testie" for Testie, Expect
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import "./strain" for Strain
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Testie.test("Strain") { |do, skip|
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do.describe("keep") {
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do.test("keep on empty list returns empty list") {
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var actual = Strain.keep([]) { |x| true }
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Expect.value(actual).toEqual([])
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}
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skip.test("keeps everything") {
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var actual = Strain.keep([1, 3, 5]) { |x| true }
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Expect.value(actual).toEqual([1, 3, 5])
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}
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skip.test("keeps nothing") {
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var actual = Strain.keep([1, 3, 5]) { |x| false }
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Expect.value(actual).toEqual([])
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}
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skip.test("keeps first and last") {
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var actual = Strain.keep([1, 2, 3]) { |x| x % 2 == 1 }
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Expect.value(actual).toEqual([1, 3])
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}
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skip.test("keeps neither first nor last") {
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var actual = Strain.keep([1, 2, 3]) { |x| x % 2 == 0 }
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Expect.value(actual).toEqual([2])
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}
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skip.test("keeps strings") {
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var list = ["apple", "zebra", "banana", "zombies", "cherimoya", "zealot"]
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var actual = Strain.keep(list) { |x| x.startsWith("z") }
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var expected = ["zebra", "zombies", "zealot"]
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Expect.value(actual).toEqual(expected)
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}
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skip.test("keeps lists") {
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var list = [
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[1, 2, 3],
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[5, 5, 5],
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[5, 1, 2],
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[2, 1, 2],
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[1, 5, 2],
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[2, 2, 1],
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[1, 2, 5]
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]
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var actual = Strain.keep(list) { |x| x.contains(5) }
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var expected = [
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[5, 5, 5],
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[5, 1, 2],
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[1, 5, 2],
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[1, 2, 5]
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]
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Expect.value(actual).toEqual(expected)
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}
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}
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do.describe("discard") {
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skip.test("discard on empty list returns empty list") {
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var actual = Strain.discard([]) { |x| true }
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Expect.value(actual).toEqual([])
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}
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skip.test("discards everything") {
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var actual = Strain.discard([1, 3, 5]) { |x| true }
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Expect.value(actual).toEqual([])
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}
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skip.test("discards nothing") {
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var actual = Strain.discard([1, 3, 5]) { |x| false }
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Expect.value(actual).toEqual([1, 3, 5])
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}
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skip.test("discards first and last") {
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var actual = Strain.discard([1, 2, 3]) { |x| x % 2 == 1 }
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Expect.value(actual).toEqual([2])
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}
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skip.test("discards neither first nor last") {
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var actual = Strain.discard([1, 2, 3]) { |x| x % 2 == 0 }
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Expect.value(actual).toEqual([1, 3])
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}
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skip.test("discards strings") {
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var list = ["apple", "zebra", "banana", "zombies", "cherimoya", "zealot"]
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var actual = Strain.discard(list) { |x| x.startsWith("z") }
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var expected = ["apple", "banana", "cherimoya"]
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Expect.value(actual).toEqual(expected)
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}
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skip.test("discards lists") {
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var list = [
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[1, 2, 3],
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[5, 5, 5],
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[5, 1, 2],
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[2, 1, 2],
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[1, 5, 2],
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[2, 2, 1],
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[1, 2, 5]
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]
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var actual = Strain.discard(list) { |x| x.contains(5) }
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var expected = [
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[1, 2, 3],
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[2, 1, 2],
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[2, 2, 1]
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]
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Expect.value(actual).toEqual(expected)
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}
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}
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}
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‎exercises/practice/strain/strain.wren

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class Strain {
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static keep(list, predicate) {
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Fiber.abort("Remove this statement and implement this function")
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}
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static discard(list, predicate) {
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Fiber.abort("Remove this statement and implement this function")
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}
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}

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