Add crypto-square (#117)

Author: glennj

config.json

@@ -594,6 +594,14 @@
         "prerequisites": [],
         "difficulty": 5
       },
+      {
+        "slug": "crypto-square",
+        "name": "Crypto Square",
+        "uuid": "7e4ad5c7-fe53-4f7b-ac20-8f4c03799194",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
+      },
       {
         "slug": "flower-field",
         "name": "Flower Field",

exercises/practice/crypto-square/.busted

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

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

@@ -0,0 +1,71 @@
+# Instructions
+
+Implement the classic method for composing secret messages called a square code.
+
+Given an English text, output the encoded version of that text.
+
+First, the input is normalized: the spaces and punctuation are removed from the English text and the message is down-cased.
+
+Then, the normalized characters are broken into rows.
+These rows can be regarded as forming a rectangle when printed with intervening newlines.
+
+For example, the sentence
+
+```text
+"If man was meant to stay on the ground, god would have given us roots."
+```
+
+is normalized to:
+
+```text
+"ifmanwasmeanttostayonthegroundgodwouldhavegivenusroots"
+```
+
+The plaintext should be organized into a rectangle as square as possible.
+The size of the rectangle should be decided by the length of the message.
+
+If `c` is the number of columns and `r` is the number of rows, then for the rectangle `r` x `c` find the smallest possible integer `c` such that:
+
+- `r * c >= length of message`,
+- and `c >= r`,
+- and `c - r <= 1`.
+
+Our normalized text is 54 characters long, dictating a rectangle with `c = 8` and `r = 7`:
+
+```text
+"ifmanwas"
+"meanttos"
+"tayonthe"
+"groundgo"
+"dwouldha"
+"vegivenu"
+"sroots  "
+```
+
+The coded message is obtained by reading down the columns going left to right.
+
+The message above is coded as:
+
+```text
+"imtgdvsfearwermayoogoanouuiontnnlvtwttddesaohghnsseoau"
+```
+
+Output the encoded text in chunks that fill perfect rectangles `(r X c)`, with `c` chunks of `r` length, separated by spaces.
+For phrases that are `n` characters short of the perfect rectangle, pad each of the last `n` chunks with a single trailing space.
+
+```text
+"imtgdvs fearwer mayoogo anouuio ntnnlvt wttddes aohghn  sseoau "
+```
+
+Notice that were we to stack these, we could visually decode the ciphertext back in to the original message:
+
+```text
+"imtgdvs"
+"fearwer"
+"mayoogo"
+"anouuio"
+"ntnnlvt"
+"wttddes"
+"aohghn "
+"sseoau "
+```

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

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "glennj"
+  ],
+  "files": {
+    "solution": [
+      "crypto_square.moon"
+    ],
+    "test": [
+      "crypto_square_spec.moon"
+    ],
+    "example": [
+      ".meta/example.moon"
+    ]
+  },
+  "blurb": "Implement the classic method for composing secret messages called a square code.",
+  "source": "J Dalbey's Programming Practice problems",
+  "source_url": "https://users.csc.calpoly.edu/~jdalbey/103/Projects/ProgrammingPractice.html"
+}

exercises/practice/crypto-square/.meta/example.moon

@@ -0,0 +1,21 @@
+pad = (str, width) -> string.format "%-#{width}s", str
+
+join = table.concat
+
+encode = (text) ->
+  clean = text\gsub('[^%a%d]', '')\lower!
+  return '' if clean == ''
+  len = math.ceil math.sqrt #clean
+
+  segments = {}
+  for i = 1, #clean, len
+    table.insert segments, clean\sub(i, i + len - 1)
+
+  -- pad the last segment
+  segments[#segments] = pad segments[#segments], len
+
+  transposed = [join [s\sub(i,i) for s in *segments] for i = 1, len]
+  join transposed, " "
+
+
+{ :encode }

exercises/practice/crypto-square/.meta/spec_generator.moon

@@ -0,0 +1,11 @@
+{
+  module_imports: {'encode'},
+
+  generate_test: (case, level) ->
+    lines = {
+      "result = encode #{quote case.input.plaintext}",
+      "expected = #{quote case.expected}",
+      "assert.are.equal expected, result"
+    }
+    table.concat [indent line, level for line in *lines], '\n'
+}

exercises/practice/crypto-square/.meta/tests.toml

@@ -0,0 +1,39 @@
+# 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.
+
+[407c3837-9aa7-4111-ab63-ec54b58e8e9f]
+description = "empty plaintext results in an empty ciphertext"
+
+[aad04a25-b8bb-4304-888b-581bea8e0040]
+description = "normalization results in empty plaintext"
+
+[64131d65-6fd9-4f58-bdd8-4a2370fb481d]
+description = "Lowercase"
+
+[63a4b0ed-1e3c-41ea-a999-f6f26ba447d6]
+description = "Remove spaces"
+
+[1b5348a1-7893-44c1-8197-42d48d18756c]
+description = "Remove punctuation"
+
+[8574a1d3-4a08-4cec-a7c7-de93a164f41a]
+description = "9 character plaintext results in 3 chunks of 3 characters"
+
+[a65d3fa1-9e09-43f9-bcec-7a672aec3eae]
+description = "8 character plaintext results in 3 chunks, the last one with a trailing space"
+
+[fbcb0c6d-4c39-4a31-83f6-c473baa6af80]
+description = "54 character plaintext results in 7 chunks, the last two with trailing spaces"
+include = false
+
+[33fd914e-fa44-445b-8f38-ff8fbc9fe6e6]
+description = "54 character plaintext results in 8 chunks, the last two with trailing spaces"
+reimplements = "fbcb0c6d-4c39-4a31-83f6-c473baa6af80"

exercises/practice/crypto-square/crypto_square.moon

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

exercises/practice/crypto-square/crypto_square_spec.moon

@@ -0,0 +1,42 @@
+import encode from require 'crypto_square'
+
+describe 'crypto-square', ->
+  it 'empty plaintext results in an empty ciphertext', ->
+    result = encode ''
+    expected = ''
+    assert.are.equal expected, result
+
+  pending 'normalization results in empty plaintext', ->
+    result = encode '... --- ...'
+    expected = ''
+    assert.are.equal expected, result
+
+  pending 'Lowercase', ->
+    result = encode 'A'
+    expected = 'a'
+    assert.are.equal expected, result
+
+  pending 'Remove spaces', ->
+    result = encode '  b '
+    expected = 'b'
+    assert.are.equal expected, result
+
+  pending 'Remove punctuation', ->
+    result = encode '@1,%!'
+    expected = '1'
+    assert.are.equal expected, result
+
+  pending '9 character plaintext results in 3 chunks of 3 characters', ->
+    result = encode 'This is fun!'
+    expected = 'tsf hiu isn'
+    assert.are.equal expected, result
+
+  pending '8 character plaintext results in 3 chunks, the last one with a trailing space', ->
+    result = encode 'Chill out.'
+    expected = 'clu hlt io '
+    assert.are.equal expected, result
+
+  pending '54 character plaintext results in 8 chunks, the last two with trailing spaces', ->
+    result = encode 'If man was meant to stay on the ground, god would have given us roots.'
+    expected = 'imtgdvs fearwer mayoogo anouuio ntnnlvt wttddes aohghn  sseoau '
+    assert.are.equal expected, result