Add sieve (#227)

config.json

@@ -134,6 +134,14 @@
           "strings"
         ]
       },
+      {
+        "slug": "sieve",
+        "name": "Sieve",
+        "uuid": "62ea1661-cdf6-4291-9c0f-3a8c911ce940",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "matching-brackets",
         "name": "Matching Brackets",

exercises/practice/sieve/.docs/instructions.md

@@ -0,0 +1,28 @@
+# Instructions
+
+Your task is to create a program that implements the Sieve of Eratosthenes algorithm to find prime numbers.
+
+A prime number is a number that is only divisible by 1 and itself.
+For example, 2, 3, 5, 7, 11, and 13 are prime numbers.
+
+The Sieve of Eratosthenes is an ancient algorithm that works by taking a list of numbers and crossing out all the numbers that aren't prime.
+
+A number that is **not** prime is called a "composite number".
+
+To use the Sieve of Eratosthenes, you first create a list of all the numbers between 2 and your given number.
+Then you repeat the following steps:
+
+1. Find the next unmarked number in your list. This is a prime number.
+2. Mark all the multiples of that prime number as composite (not prime).
+
+You keep repeating these steps until you've gone through every number in your list.
+At the end, all the unmarked numbers are prime.
+
+~~~~exercism/note
+[Wikipedia's Sieve of Eratosthenes article][eratosthenes] has a useful graphic that explains the algorithm.
+
+The tests don't check that you've implemented the algorithm, only that you've come up with the correct list of primes.
+A good first test is to check that you do not use division or remainder operations.
+
+[eratosthenes]: https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes
+~~~~

exercises/practice/sieve/.docs/introduction.md

@@ -0,0 +1,7 @@
+# Introduction
+
+You bought a big box of random computer parts at a garage sale.
+You've started putting the parts together to build custom computers.
+
+You want to test the performance of different combinations of parts, and decide to create your own benchmarking program to see how your computers compare.
+You choose the famous "Sieve of Eratosthenes" algorithm, an ancient algorithm, but one that should push your computers to the limits.

exercises/practice/sieve/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "source/sieve.d"
+    ],
+    "test": [
+      "source/sieve.d"
+    ],
+    "example": [
+      "example/sieve.d"
+    ]
+  },
+  "blurb": "Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.",
+  "source": "Sieve of Eratosthenes at Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes"
+}

exercises/practice/sieve/.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.
+
+[88529125-c4ce-43cc-bb36-1eb4ddd7b44f]
+description = "no primes under two"
+
+[4afe9474-c705-4477-9923-840e1024cc2b]
+description = "find first prime"
+
+[974945d8-8cd9-4f00-9463-7d813c7f17b7]
+description = "find primes up to 10"
+
+[2e2417b7-3f3a-452a-8594-b9af08af6d82]
+description = "limit is prime"
+
+[92102a05-4c7c-47de-9ed0-b7d5fcd00f21]
+description = "find primes up to 1000"

exercises/practice/sieve/dub.sdl

@@ -0,0 +1,2 @@
+name "sieve"
+buildRequirements "disallowDeprecations"

exercises/practice/sieve/example/sieve.d

@@ -0,0 +1,20 @@
+module sieve;
+
+import std.algorithm;
+import std.array;
+import std.range;
+
+pure int[] primes(immutable int limit)
+{
+    int[] results = [];
+    int[] nums = iota(2, limit + 1).array;
+    while (nums.length > 0)
+    {
+        int current = nums.front;
+        results ~= nums.front;
+
+        nums = nums.dropOne().filter!(n => n % current != 0).array;
+    }
+
+    return results;
+}

exercises/practice/sieve/source/sieve.d

@@ -0,0 +1,56 @@
+module sieve;
+
+pure int[] primes(immutable int limit)
+{
+    // implement this function
+}
+
+unittest
+{
+    immutable int allTestsEnabled = 0;
+
+    // no primes under two
+    {
+        assert(primes(1) == []);
+    }
+
+    static if (allTestsEnabled)
+    {
+        // find first prime
+        {
+            assert(primes(2) == [2]);
+        }
+
+        // find primes up to 10
+        {
+            assert(primes(10) == [2, 3, 5, 7]);
+        }
+
+        // limit is prime
+        {
+            assert(primes(13) == [2, 3, 5, 7, 11, 13]);
+        }
+
+        // find primes up to 1000
+        {
+            const int[] expected = [
+                2,   3,   5,   7,   11,  13,  17,  19,  23,  29,  31,  37,  41,  43,
+                47,  53,  59,  61,  67,  71,  73,  79,  83,  89,  97,  101, 103, 107,
+                109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181,
+                191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263,
+                269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349,
+                353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433,
+                439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521,
+                523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613,
+                617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701,
+                709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809,
+                811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887,
+                907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997
+            ];
+
+            assert(primes(1000) == expected);
+        }
+
+    }
+
+}