nth-prime

config.json

@@ -366,6 +366,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 4
+      },
+      {
+        "slug": "nth-prime",
+        "name": "Nth Prime",
+        "uuid": "a0dc033f-e760-4f34-abf4-850451044ba5",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4
       }
     ]
   },

exercises/practice/nth-prime/.busted

@@ -0,0 +1,5 @@
+return {
+  default = {
+    ROOT = { '.' }
+  }
+}

exercises/practice/nth-prime/.docs/instructions.md

@@ -0,0 +1,7 @@
+# Instructions
+
+Given a number n, determine what the nth prime is.
+
+By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13.
+
+If your language provides methods in the standard library to deal with prime numbers, pretend they don't exist and implement them yourself.

exercises/practice/nth-prime/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "glennj"
+  ],
+  "files": {
+    "solution": [
+      "nth_prime.moon"
+    ],
+    "test": [
+      "nth_prime_spec.moon"
+    ],
+    "example": [
+      ".meta/example.moon"
+    ]
+  },
+  "blurb": "Given a number n, determine what the nth prime is.",
+  "source": "A variation on Problem 7 at Project Euler",
+  "source_url": "https://projecteuler.net/problem=7"
+}

exercises/practice/nth-prime/.meta/example.moon

@@ -0,0 +1,37 @@
+-- a coroutine wrapped up in a closure
+prime_generator = ->
+  primes = {}
+
+  is_prime = (n) ->
+    sqrt = math.sqrt n
+    for p in *primes
+      return true if p > sqrt
+      return false if n % p == 0
+    true
+
+  coroutine.wrap ->
+    coroutine.yield 2
+    table.insert primes, 2
+    p = 3
+    while true
+      coroutine.yield p
+      table.insert primes, p
+      incrementing = true
+      while incrementing
+        p += 2
+        incrementing = not is_prime p
+
+
+nth_prime = (n) ->
+  assert n > 0, 'there is no zeroth prime'
+
+  next_prime = prime_generator!
+  i = 0
+
+  while true
+    prime = next_prime!
+    i += 1
+    return prime if i == n
+
+
+{ prime: nth_prime }

exercises/practice/nth-prime/.meta/spec_generator.moon

@@ -0,0 +1,9 @@
+{
+  module_imports: {'prime'},
+
+  generate_test: (case, level) ->
+    if type(case.expected) == 'number'
+      indent "assert.are.equal #{case.expected}, prime #{case.input.number}", level
+    else
+      indent "assert.has.errors (-> prime #{case.input.number}), #{quote case.expected.error}", level
+}

exercises/practice/nth-prime/.meta/tests.toml

@@ -0,0 +1,25 @@
+# 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.
+
+[75c65189-8aef-471a-81de-0a90c728160c]
+description = "first prime"
+
+[2c38804c-295f-4701-b728-56dea34fd1a0]
+description = "second prime"
+
+[56692534-781e-4e8c-b1f9-3e82c1640259]
+description = "sixth prime"
+
+[fce1e979-0edb-412d-93aa-2c744e8f50ff]
+description = "big prime"
+
+[bd0a9eae-6df7-485b-a144-80e13c7d55b2]
+description = "there is no zeroth prime"

exercises/practice/nth-prime/nth_prime.moon

@@ -0,0 +1,4 @@
+{
+  prime: (n) ->
+    error 'Implement me'
+}

exercises/practice/nth-prime/nth_prime_spec.moon

@@ -0,0 +1,17 @@
+import prime from require 'nth_prime'
+
+describe 'nth-prime', ->
+  it 'first prime', ->
+    assert.are.equal 2, prime 1
+
+  pending 'second prime', ->
+    assert.are.equal 3, prime 2
+
+  pending 'sixth prime', ->
+    assert.are.equal 13, prime 6
+
+  pending 'big prime', ->
+    assert.are.equal 104743, prime 10001
+
+  pending 'there is no zeroth prime', ->
+    assert.has.errors (-> prime 0), 'there is no zeroth prime'