Add strain exercise (#222)

config.json

@@ -331,6 +331,14 @@
         "prerequisites": [],
         "difficulty": 1
       },
+      {
+        "slug": "strain",
+        "name": "Strain",
+        "uuid": "5a1a2fa9-e8d0-4784-ba0c-c53fb8405e26",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "sum-of-multiples",
         "name": "Sum of Multiples",

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

@@ -0,0 +1,29 @@
+# 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.

exercises/practice/strain/.meta/Example.cfc

@@ -0,0 +1,27 @@
+/**
+* Here is an example solution for the Strain exercise
+*/
+component {
+
+	/**
+	* @returns 
+	*/
+	function keep(list, predicate) {
+		var results = [];
+		for (elem in list) {
+			if (predicate(elem)) {
+				arrayAppend(results, elem);
+			}
+		}
+
+		return results;
+	}
+
+	/**
+	* @returns 
+	*/
+	function discard(list, predicate) {
+		var newPredicate = function( x ) {return not predicate(x); } 
+		return keep(list, newPredicate);
+	}
+}

exercises/practice/strain/.meta/ExampleTest.cfc

@@ -0,0 +1,7 @@
+component extends="StrainTest" {
+
+	function beforeAll(){
+	  SUT = createObject( 'Solution' );
+	}
+
+}

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

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "Strain.cfc"
+    ],
+    "test": [
+      "StrainTest.cfc"
+    ],
+    "example": [
+      ".meta/Example.cfc"
+    ]
+  },
+  "blurb": "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.",
+  "source": "Conversation with James Edward Gray II",
+  "source_url": "http://graysoftinc.com/"
+}

exercises/practice/strain/.meta/tests.toml

@@ -0,0 +1,52 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[26af8c32-ba6a-4eb3-aa0a-ebd8f136e003]
+description = "keep on empty list returns empty list"
+
+[f535cb4d-e99b-472a-bd52-9fa0ffccf454]
+description = "keeps everything"
+
+[950b8e8e-f628-42a8-85e2-9b30f09cde38]
+description = "keeps nothing"
+
+[92694259-6e76-470c-af87-156bdf75018a]
+description = "keeps first and last"
+
+[938f7867-bfc7-449e-a21b-7b00cbb56994]
+description = "keeps neither first nor last"
+
+[8908e351-4437-4d2b-a0f7-770811e48816]
+description = "keeps strings"
+
+[2728036b-102a-4f1e-a3ef-eac6160d876a]
+description = "keeps lists"
+
+[ef16beb9-8d84-451a-996a-14e80607fce6]
+description = "discard on empty list returns empty list"
+
+[2f42f9bc-8e06-4afe-a222-051b5d8cd12a]
+description = "discards everything"
+
+[ca990fdd-08c2-4f95-aa50-e0f5e1d6802b]
+description = "discards nothing"
+
+[71595dae-d283-48ca-a52b-45fa96819d2f]
+description = "discards first and last"
+
+[ae141f79-f86d-4567-b407-919eaca0f3dd]
+description = "discards neither first nor last"
+
+[daf25b36-a59f-4f29-bcfe-302eb4e43609]
+description = "discards strings"
+
+[a38d03f9-95ad-4459-80d1-48e937e4acaf]
+description = "discards lists"

exercises/practice/strain/Strain.cfc

@@ -0,0 +1,19 @@
+/**
+* Your implementation of the Strain exercise
+*/
+component {
+
+	/**
+	* @returns 
+	*/
+	function keep(list, predicate) {
+		// Implement me here
+	}
+
+	/**
+	* @returns 
+	*/
+	function discard(list, predicate) {
+		// Implement me here
+	}
+}

exercises/practice/strain/StrainTest.cfc

@@ -0,0 +1,120 @@
+component extends="testbox.system.BaseSpec" {
+
+	function beforeAll(){
+	  SUT = createObject( 'Strain' );
+	}
+
+	function alwaysTrue( x ) { return true; }
+
+	function alwaysFalse( x ) { return false; }
+
+	function isOdd( x ) { return x % 2 == 1; }
+
+	function isEven( x ) { return x % 2 == 0; }
+
+	function containsFive( x ) { return arrayContains(x, 5); }
+
+	function startWithZ( x ) { return left(x, 1) == 'z'; }
+
+	function run(){
+
+		describe( "My Strain class", function(){			
+
+			it( 'keep on empty list returns empty list', function(){
+				expect( SUT.keep( list=[], predicate=alwaysTrue ) ).toBe( [] );
+			});
+
+			it( 'keeps everything', function(){
+				expect( SUT.keep( list=[1, 3, 5], predicate=alwaysTrue ) ).toBe( [1,3,5] );
+			});
+
+			it( 'keeps nothing', function(){
+				expect( SUT.keep( list=[1, 3, 5], predicate=alwaysFalse) ).toBe( [] );
+			});
+
+			it( 'keeps first and last', function(){
+				expect( SUT.keep( list=[1, 2, 3], predicate=isOdd ) ).toBe( [1,3] );
+			});
+
+			it( 'keeps neither first nor last', function(){
+				expect( SUT.keep( list=[1, 2, 3], predicate=isEven ) ).toBe( [2] );
+			});
+
+			it( 'keeps strings', function(){
+				expect( SUT.keep(
+					list=["apple",
+						  "zebra",
+						  "banana",
+						  "zombies",
+						  "cherimoya",
+						  "zealot"],
+					predicate=startWithZ ) ).toBe( ["zebra","zombies","zealot"] );
+			});
+
+			it( 'keeps lists', function(){
+				expect( SUT.keep(
+					list=[[1, 2, 3],
+						  [5, 5, 5],
+						  [5, 1, 2],
+						  [2, 1, 2],
+						  [1, 5, 2],
+						  [2, 2, 1],
+						  [1, 2, 5]],
+					predicate=containsFive ) ).toBe( [[5,5,5],
+													  [5,1,2],
+													  [1,5,2],
+													  [1,2,5]] );
+			});
+
+			it( 'discard on empty list returns empty list', function(){
+				expect( SUT.discard( list=[], predicate=alwaysTrue ) ).toBe( [] );
+			});
+
+			it( 'discards everything', function(){
+				expect( SUT.discard( list=[1, 3, 5], predicate=alwaysTrue ) ).toBe( [] );
+			});
+
+			it( 'discards nothing', function(){
+				expect( SUT.discard( list=[1, 3, 5], predicate=alwaysFalse ) ).toBe( [1,3,5] );
+			});
+
+			it( 'discards first and last', function(){
+				expect( SUT.discard( list=[1, 2, 3], predicate=isOdd ) ).toBe( [2] );
+			});
+
+			it( 'discards neither first nor last', function(){
+				expect( SUT.discard( list=[1, 2, 3], predicate=isEven ) ).toBe( [1,3] );
+			});
+
+			it( 'discards strings', function(){
+				expect( SUT.discard(
+					list=["apple",
+						  "zebra",
+						  "banana",
+						  "zombies",
+						  "cherimoya",
+						  "zealot"],
+					predicate=startWithZ ) ).toBe( ["apple",
+													"banana",
+													"cherimoya"] );
+			});
+
+			it( 'discards lists', function(){
+				expect( SUT.discard(
+					list=[[1, 2, 3],
+						  [5, 5, 5],
+						  [5, 1, 2],
+						  [2, 1, 2],
+						  [1, 5, 2],
+						  [2, 2, 1],
+						  [1, 2, 5]],
+					predicate=containsFive ) ).toBe( [[1,2,3],
+													  [2,1,2],
+													  [2,2,1]] );
+			});
+
+		});
+
+	}
+
+}containsFive