Add proverb exercise

config.json

@@ -752,7 +752,7 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 1
-      },      
+      },
       {
         "slug": "resistor-color-duo",
         "name": "Resistor Color Duo",
@@ -768,6 +768,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 3
+      },
+      {
+        "slug": "proverb",
+        "name": "Proverb",
+        "uuid": "88b06132-be17-4105-8184-90c2d571fcb2",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
       }
     ]
   },

exercises/practice/proverb/.docs/instructions.md

@@ -0,0 +1,19 @@
+# Instructions
+
+For want of a horseshoe nail, a kingdom was lost, or so the saying goes.
+
+Given a list of inputs, generate the relevant proverb.
+For example, given the list `["nail", "shoe", "horse", "rider", "message", "battle", "kingdom"]`, you will output the full text of this proverbial rhyme:
+
+```text
+For want of a nail the shoe was lost.
+For want of a shoe the horse was lost.
+For want of a horse the rider was lost.
+For want of a rider the message was lost.
+For want of a message the battle was lost.
+For want of a battle the kingdom was lost.
+And all for the want of a nail.
+```
+
+Note that the list of inputs may vary; your solution should be able to handle lists of arbitrary length and content.
+No line of the output text should be a static, unchanging string; all should vary according to the input given.

exercises/practice/proverb/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "erikschierboom"
+  ],
+  "files": {
+    "solution": [
+      "proverb.R"
+    ],
+    "test": [
+      "test_proverb.R"
+    ],
+    "example": [
+      ".meta/example.R"
+    ]
+  },
+  "blurb": "For want of a horseshoe nail, a kingdom was lost, or so the saying goes. Output the full text of this proverbial rhyme.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/For_Want_of_a_Nail"
+}

exercises/practice/proverb/.meta/example.R

@@ -0,0 +1,16 @@
+verse_line <- function(want, lost) {
+  paste("For want of a", want, "the", lost, "was lost.")
+}
+
+verse_ending <- function(want) {
+  paste("And all for the want of a ", want, ".", sep = "")
+}
+
+recite <- function(wanted) {
+  if (is.null(wanted)) {
+    return(c())
+  }
+
+  lines <- mapply(verse_line, wanted, c(wanted[-1], NA))[-length(wanted)]
+  c(unname(lines), verse_ending(wanted[[1]]))
+}

exercises/practice/proverb/.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.
+
+[e974b73e-7851-484f-8d6d-92e07fe742fc]
+description = "zero pieces"
+
+[2fcd5f5e-8b82-4e74-b51d-df28a5e0faa4]
+description = "one piece"
+
+[d9d0a8a1-d933-46e2-aa94-eecf679f4b0e]
+description = "two pieces"
+
+[c95ef757-5e94-4f0d-a6cb-d2083f5e5a83]
+description = "three pieces"
+
+[433fb91c-35a2-4d41-aeab-4de1e82b2126]
+description = "full proverb"
+
+[c1eefa5a-e8d9-41c7-91d4-99fab6d6b9f7]
+description = "four pieces modernized"

exercises/practice/proverb/proverb.R

@@ -0,0 +1,3 @@
+recite <- function(wanted) {
+
+}

exercises/practice/proverb/test_proverb.R

@@ -0,0 +1,62 @@
+source("./proverb.R")
+library(testthat)
+
+test_that("Zero pieces", {
+  wanted <- c()
+  expected <- c()
+  expect_equal(recite(wanted), expected)
+})
+
+test_that("One piece", {
+  wanted <- c("nail")
+  expected <- c("And all for the want of a nail.")
+  expect_equal(recite(wanted), expected)
+})
+
+test_that("Two pieces", {
+  wanted <- c("nail", "shoe")
+  expected <-
+    c(
+      "For want of a nail the shoe was lost.",
+      "And all for the want of a nail."
+    )
+  expect_equal(recite(wanted), expected)
+})
+
+test_that("Three pieces", {
+  wanted <- c("nail", "shoe", "horse")
+  expected <-
+    c(
+      "For want of a nail the shoe was lost.",
+      "For want of a shoe the horse was lost.",
+      "And all for the want of a nail."
+    )
+  expect_equal(recite(wanted), expected)
+})
+
+test_that("Full proverb", {
+  wanted <- c("nail", "shoe", "horse", "rider", "message", "battle", "kingdom")
+  expected <-
+    c(
+      "For want of a nail the shoe was lost.",
+      "For want of a shoe the horse was lost.",
+      "For want of a horse the rider was lost.",
+      "For want of a rider the message was lost.",
+      "For want of a message the battle was lost.",
+      "For want of a battle the kingdom was lost.",
+      "And all for the want of a nail."
+    )
+  expect_equal(recite(wanted), expected)
+})
+
+test_that("Four pieces modernized", {
+  wanted <- c("pin", "gun", "soldier", "battle")
+  expected <-
+    c(
+      "For want of a pin the gun was lost.",
+      "For want of a gun the soldier was lost.",
+      "For want of a soldier the battle was lost.",
+      "And all for the want of a pin."
+    )
+  expect_equal(recite(wanted), expected)
+})