Add sieve exercise (#206)

config.json

@@ -380,6 +380,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 1
+      },
+      {
+        "slug": "sieve",
+        "name": "Sieve",
+        "uuid": "50f4505d-c82a-46a7-bfeb-0100c5f2d45f",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 1
       }
     ]
   },

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": [
+    "kahgoh"
+  ],
+  "files": {
+    "solution": [
+      "src/sieve.lfe"
+    ],
+    "test": [
+      "test/sieve-tests.lfe"
+    ],
+    "example": [
+      ".meta/example.lfe"
+    ]
+  },
+  "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/example.lfe

@@ -0,0 +1,19 @@
+(defmodule sieve
+  (export (primes 1)))
+
+(defun mark (n limit composite)
+  (sets:union composite (sets:from_list (lists:seq (* n 2) limit n))))
+
+(defun do-primes  
+  ((limit limit primes composite) 
+    (if (sets:is_element limit composite)
+      primes
+      (cons limit primes)))
+  ((n limit primes composite) 
+    (if (sets:is_element n composite) 
+      (do-primes (+ n 1) limit primes composite)
+      (do-primes (+ n 1) limit (cons n primes) (mark n limit composite)))))
+
+(defun primes 
+  ((limit) (when (< limit 2)) '())
+  ((limit) (lists:reverse (do-primes 2 limit '() (sets:new)))))

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/Makefile

@@ -0,0 +1,21 @@
+ERL    := $(shell which erl)
+REBAR3 := $(shell which rebar3)
+
+null  :=
+space := $(null) #
+comma := ,
+
+ifeq ($(ERL),)
+  $(error Can't find Erlang executable 'erl')
+else ifeq ($(REBAR3),)
+  $(error Can't find rebar3)
+endif
+
+compile: ; $(REBAR3) compile
+
+clean: ; $(REBAR3) clean
+
+.PHONY: test
+test:
+	$(REBAR3) eunit \
+	-m $(subst $(space),$(comma),$(basename $(notdir $(wildcard test/*.lfe))))

exercises/practice/sieve/rebar.config

@@ -0,0 +1,11 @@
+{plugins, [{rebar3_lfe, "0.4.3"}]}.
+
+{provider_hooks, [{post, [{compile, {lfe, compile}}]}]}.
+
+{deps, [{lfe, "2.1.1"}]}.
+
+{profiles,
+ [{test,
+   [{eunit_compile_opts, [{src_dirs, ["src", "test"]}]},
+    {deps,
+     [{ltest, "0.13.3"}]}]}]}.

exercises/practice/sieve/rebar.lock

@@ -0,0 +1,8 @@
+{"1.2.0",
+[{<<"lfe">>,{pkg,<<"lfe">>,<<"2.1.1">>},0}]}.
+[
+{pkg_hash,[
+ {<<"lfe">>, <<"4A888B26172D198DC7A5AFEB897E8248AF7D56E1638D9C8249AAF933AE811B96">>}]},
+{pkg_hash_ext,[
+ {<<"lfe">>, <<"C484D3B655D40DED58BC41B17B22F173711C681BF36063A234A9BAA9506947E1">>}]}
+].

exercises/practice/sieve/src/sieve.app.src

@@ -0,0 +1,11 @@
+%% -*- erlang -*-
+{application, 'sieve',
+ [{description, "Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number."},
+  {vsn, "0.0.1"},
+  {modules,
+   ['sieve']},
+  {registered, []},
+  {applications,
+   [kernel, stdlib]},
+  {included_applications, []},
+  {env, []}]}.

exercises/practice/sieve/src/sieve.lfe

@@ -0,0 +1,6 @@
+(defmodule sieve
+  (export (primes 1)))
+
+(defun primes (limit)
+  ; Please implement the primes function
+)

exercises/practice/sieve/test/sieve-tests.lfe

@@ -0,0 +1,32 @@
+(defmodule sieve-tests
+  (behaviour ltest-unit)
+  (export all))
+
+(include-lib "ltest/include/ltest-macros.lfe")
+
+(deftest test-no-primes-under-two
+  (is-equal (sieve:primes 1) '()))
+
+(deftest test-find-first-prime
+  (is-equal (sieve:primes 2) '(2)))
+
+(deftest test-find-primes-up-to-10
+  (is-equal (sieve:primes 10) '(2 3 5 7)))
+
+(deftest test-limit-is-a-prime
+  (is-equal (sieve:primes 13) '(2 3 5 7 11 13)))
+
+(deftest test-find-primes-up-to-1000
+  (is-equal (sieve:primes 1000) '(
+      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)))