Add reverse-string exercise (#498)

Author: BNAndras

config.json

@@ -114,6 +114,14 @@
         "difficulty": 2,
         "topics": null
       },
+      {
+        "slug": "reverse-string",
+        "name": "Reverse String",
+        "uuid": "58c93fbe-5c57-41d0-9085-6007a488aaca",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "rna-transcription",
         "name": "RNA Transcription",

exercises/practice/reverse-string/.docs/instructions.md

@@ -0,0 +1,7 @@
+# Instructions
+
+Reverse a string
+
+For example:
+input: "cool"
+output: "looc"

exercises/practice/reverse-string/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "reverse_string.ml"
+    ],
+    "test": [
+      "test.ml"
+    ],
+    "example": [
+      ".meta/example.ml"
+    ]
+  },
+  "blurb": "Reverse a string.",
+  "source": "Introductory challenge to reverse an input string",
+  "source_url": "https://medium.freecodecamp.org/how-to-reverse-a-string-in-javascript-in-3-different-ways-75e4763c68cb"
+}

exercises/practice/reverse-string/.meta/example.ml

@@ -0,0 +1,3 @@
+let reverse_string str =
+  let len = String.length str in
+  String.init len (fun i -> str.[len - 1 - i])

exercises/practice/reverse-string/.meta/tests.toml

@@ -0,0 +1,28 @@
+# 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.
+
+[c3b7d806-dced-49ee-8543-933fd1719b1c]
+description = "an empty string"
+
+[01ebf55b-bebb-414e-9dec-06f7bb0bee3c]
+description = "a word"
+
+[0f7c07e4-efd1-4aaa-a07a-90b49ce0b746]
+description = "a capitalized word"
+
+[71854b9c-f200-4469-9f5c-1e8e5eff5614]
+description = "a sentence with punctuation"
+
+[1f8ed2f3-56f3-459b-8f3e-6d8d654a1f6c]
+description = "a palindrome"
+
+[b9e7dec1-c6df-40bd-9fa3-cd7ded010c4c]
+description = "an even-sized word"

exercises/practice/reverse-string/Makefile

@@ -0,0 +1,9 @@
+default: clean test
+
+test: 
+	dune runtest
+
+clean:
+	dune clean
+
+.PHONY: clean

exercises/practice/reverse-string/dune

@@ -0,0 +1,16 @@
+(executable
+ (name test)
+ (libraries base ounit2))
+
+(alias
+  (name    runtest)
+  (deps    (:x test.exe))
+  (action  (run %{x})))
+
+(alias
+  (name    buildtest)
+  (deps    (:x test.exe)))
+
+(env
+  (dev
+    (flags (:standard -warn-error -A))))

exercises/practice/reverse-string/dune-project

@@ -0,0 +1 @@
+(lang dune 1.1)

exercises/practice/reverse-string/reverse_string.ml

@@ -0,0 +1,2 @@
+let reverse_string _ =
+    failwith "'reverse_string' is missing"

exercises/practice/reverse-string/reverse_string.mli

@@ -0,0 +1 @@
+val reverse_string : string -> string