Square root exercise (#548)

Author: TheRealOwenRees

config.json

@@ -598,6 +598,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 3
+      },
+      {
+        "slug": "square-root",
+        "name": "Square Root",
+        "uuid": "33360ed8-c49c-4c7f-a1fb-7e242b0794c0",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
       }
     ]
   },

exercises/practice/square-root/.docs/instructions.md

@@ -0,0 +1,18 @@
+# Instructions
+
+Your task is to calculate the square root of a given number.
+
+- Try to avoid using the pre-existing math libraries of your language.
+- As input you'll be given a positive whole number, i.e. 1, 2, 3, 4…
+- You are only required to handle cases where the result is a positive whole number.
+
+Some potential approaches:
+
+- Linear or binary search for a number that gives the input number when squared.
+- Successive approximation using Newton's or Heron's method.
+- Calculating one digit at a time or one bit at a time.
+
+You can check out the Wikipedia pages on [integer square root][integer-square-root] and [methods of computing square roots][computing-square-roots] to help with choosing a method of calculation.
+
+[integer-square-root]: https://en.wikipedia.org/wiki/Integer_square_root
+[computing-square-roots]: https://en.wikipedia.org/wiki/Methods_of_computing_square_roots

exercises/practice/square-root/.docs/introduction.md

@@ -0,0 +1,10 @@
+# Introduction
+
+We are launching a deep space exploration rocket and we need a way to make sure the navigation system stays on target.
+
+As the first step in our calculation, we take a target number and find its square root (that is, the number that when multiplied by itself equals the target number).
+
+The journey will be very long.
+To make the batteries last as long as possible, we had to make our rocket's onboard computer very power efficient.
+Unfortunately that means that we can't rely on fancy math libraries and functions, as they use more power.
+Instead we want to implement our own square root calculation.

exercises/practice/square-root/.meta/config.json

@@ -0,0 +1,20 @@
+{
+  "authors": ["therealowenrees"],
+  "files": {
+    "solution": [
+      "square_root.ml"
+    ],
+    "test": [
+      "test.ml"
+    ],
+    "example": [
+      ".meta/example.ml"
+    ],
+    "editor": [
+      "square_root.mli"
+    ]
+  },
+  "blurb": "Given a natural radicand, return its square root.",
+  "source": "wolf99",
+  "source_url": "https://github.com/exercism/problem-specifications/pull/1582"
+}

exercises/practice/square-root/.meta/example.ml

@@ -0,0 +1,10 @@
+let square_root n =
+  let radicand = float_of_int n in
+  let rec aux guess =
+    let next = 0.5 *. (guess +. radicand /. guess) in
+    match abs_float (next -. guess) with
+    | diff when diff < 0.0001 -> int_of_float next
+    | _ -> aux next
+  in
+  if n < 0 then invalid_arg "square_root: negative input"
+  else aux (radicand /. 2.0)

exercises/practice/square-root/.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.
+
+[9b748478-7b0a-490c-b87a-609dacf631fd]
+description = "root of 1"
+
+[7d3aa9ba-9ac6-4e93-a18b-2e8b477139bb]
+description = "root of 4"
+
+[6624aabf-3659-4ae0-a1c8-25ae7f33c6ef]
+description = "root of 25"
+
+[93beac69-265e-4429-abb1-94506b431f81]
+description = "root of 81"
+
+[fbddfeda-8c4f-4bc4-87ca-6991af35360e]
+description = "root of 196"
+
+[c03d0532-8368-4734-a8e0-f96a9eb7fc1d]
+description = "root of 65025"

exercises/practice/square-root/Makefile

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

exercises/practice/square-root/dune

@@ -0,0 +1,20 @@
+(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/square-root/dune-project

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

exercises/practice/square-root/square_root.ml

@@ -0,0 +1,2 @@
+let square_root _ =
+  failwith = "square root not implemented"