add resistor-color-trio exercise (#434)

Author: kmarker1101

config.json

@@ -934,6 +934,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 5
+      },
+      {
+        "slug": "resistor-color-trio",
+        "name": "Resistor Color Trio",
+        "uuid": "e63a974b-1d30-4323-8059-98d131d52f6e",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
       }
     ]
   },

exercises/practice/resistor-color-trio/.docs/instructions.md

@@ -0,0 +1,56 @@
+# Instructions
+
+If you want to build something using a Raspberry Pi, you'll probably use _resistors_.
+For this exercise, you need to know only three things about them:
+
+- Each resistor has a resistance value.
+- Resistors are small - so small in fact that if you printed the resistance value on them, it would be hard to read.
+  To get around this problem, manufacturers print color-coded bands onto the resistors to denote their resistance values.
+- Each band acts as a digit of a number.
+  For example, if they printed a brown band (value 1) followed by a green band (value 5), it would translate to the number 15.
+  In this exercise, you are going to create a helpful program so that you don't have to remember the values of the bands.
+  The program will take 3 colors as input, and outputs the correct value, in ohms.
+  The color bands are encoded as follows:
+
+- Black: 0
+- Brown: 1
+- Red: 2
+- Orange: 3
+- Yellow: 4
+- Green: 5
+- Blue: 6
+- Violet: 7
+- Grey: 8
+- White: 9
+
+In Resistor Color Duo you decoded the first two colors.
+For instance: orange-orange got the main value `33`.
+The third color stands for how many zeros need to be added to the main value.
+The main value plus the zeros gives us a value in ohms.
+For the exercise it doesn't matter what ohms really are.
+For example:
+
+- orange-orange-black would be 33 and no zeros, which becomes 33 ohms.
+- orange-orange-red would be 33 and 2 zeros, which becomes 3300 ohms.
+- orange-orange-orange would be 33 and 3 zeros, which becomes 33000 ohms.
+
+(If Math is your thing, you may want to think of the zeros as exponents of 10.
+If Math is not your thing, go with the zeros.
+It really is the same thing, just in plain English instead of Math lingo.)
+
+This exercise is about translating the colors into a label:
+
+> "... ohms"
+
+So an input of `"orange", "orange", "black"` should return:
+
+> "33 ohms"
+
+When we get to larger resistors, a [metric prefix][metric-prefix] is used to indicate a larger magnitude of ohms, such as "kiloohms".
+That is similar to saying "2 kilometers" instead of "2000 meters", or "2 kilograms" for "2000 grams".
+
+For example, an input of `"orange", "orange", "orange"` should return:
+
+> "33 kiloohms"
+
+[metric-prefix]: https://en.wikipedia.org/wiki/Metric_prefix

exercises/practice/resistor-color-trio/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "kmarker1101"
+  ],
+  "files": {
+    "solution": [
+      "resistor-color-trio.el"
+    ],
+    "test": [
+      "resistor-color-trio-test.el"
+    ],
+    "example": [
+      ".meta/example.el"
+    ]
+  },
+  "blurb": "Convert color codes, as used on resistors, to a human-readable label.",
+  "source": "Maud de Vries, Erik Schierboom",
+  "source_url": "https://github.com/exercism/problem-specifications/issues/1549"
+}

exercises/practice/resistor-color-trio/.meta/example.el

@@ -0,0 +1,40 @@
+;;; resistor-color-trio.el --- Resistor Color Trio (exercism)  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;;; Code:
+
+
+(setq band-values
+      '(("black"  . 0)
+	("brown"  . 1)
+	("red"    . 2)
+	("orange" . 3)
+	("yellow" . 4)
+	("green"  . 5)
+	("blue"   . 6)
+	("violet" . 7)
+	("grey"   . 8)
+	("white"  . 9)))
+
+
+(defun label (colors)
+  (let* ((color-1 (nth 0 colors))
+         (color-2 (nth 1 colors))
+         (color-3 (nth 2 colors))
+         (value (+ (* (cdr (assoc color-1 band-values)) 10)
+                   (cdr (assoc color-2 band-values))))
+         (resistance (* value (expt 10 (cdr (assoc color-3 band-values))))))
+    (cond
+     ((< resistance 1000)
+      (format "%d ohms" resistance))
+     ((< resistance 1000000)
+      (format "%d kiloohms" (/ resistance 1000)))
+     ((< resistance 1000000000)
+      (format "%d megaohms" (/ resistance 1000000)))
+     (t
+      (format "%d gigaohms" (/ resistance 1000000000))))))
+
+
+(provide 'resistor-color-trio)
+;;; resistor-color-trio.el ends here

exercises/practice/resistor-color-trio/.meta/tests.toml

@@ -0,0 +1,40 @@
+# 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.
+
+[d6863355-15b7-40bb-abe0-bfb1a25512ed]
+description = "Orange and orange and black"
+
+[1224a3a9-8c8e-4032-843a-5224e04647d6]
+description = "Blue and grey and brown"
+
+[b8bda7dc-6b95-4539-abb2-2ad51d66a207]
+description = "Red and black and red"
+
+[5b1e74bc-d838-4eda-bbb3-eaba988e733b]
+description = "Green and brown and orange"
+
+[f5d37ef9-1919-4719-a90d-a33c5a6934c9]
+description = "Yellow and violet and yellow"
+
+[5f6404a7-5bb3-4283-877d-3d39bcc33854]
+description = "Blue and violet and blue"
+
+[7d3a6ab8-e40e-46c3-98b1-91639fff2344]
+description = "Minimum possible value"
+
+[ca0aa0ac-3825-42de-9f07-dac68cc580fd]
+description = "Maximum possible value"
+
+[0061a76c-903a-4714-8ce2-f26ce23b0e09]
+description = "First two colors make an invalid octal number"
+
+[30872c92-f567-4b69-a105-8455611c10c4]
+description = "Ignore extra colors"

exercises/practice/resistor-color-trio/resistor-color-trio-test.el

@@ -0,0 +1,53 @@
+;;; resistor-color-trio-test.el --- Resistor Color Trio (exercism)  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;;; Code:
+
+
+(load-file "resistor-color-trio.el")
+(declare-function label "resistor-color-trio.el" (colors))
+
+
+(ert-deftest orange-and-orange-and-black ()
+  (should (string= (label '("orange" "orange" "black"))
+                   "33 ohms")))
+
+(ert-deftest blue-and-grey-and-brown ()
+  (should (string= (label '("blue" "grey" "brown"))
+                   "680 ohms")))
+
+(ert-deftest red-and-black-and-red ()
+  (should (string= (label '("red" "black" "red"))
+                   "2 kiloohms")))
+
+(ert-deftest green-and-brown-and-orange ()
+  (should (string= (label '("green" "brown" "orange"))
+                   "51 kiloohms")))
+
+(ert-deftest yellow-and-violet-and-yellow ()
+  (should (string= (label '("yellow" "violet" "yellow"))
+                   "470 kiloohms")))
+
+(ert-deftest blue-and-violet-and-blue ()
+  (should (string= (label '("blue" "violet" "blue"))
+                   "67 megaohms")))
+
+(ert-deftest minimum-possible-value ()
+  (should (string= (label '("black" "black" "black"))
+                   "0 ohms")))
+
+(ert-deftest maximum-possible-value ()
+  (should (string= (label '("white" "white" "white"))
+                   "99 gigaohms")))
+
+(ert-deftest first-two-colors-make-an-invalid-octal-number ()
+  (should (string= (label '("black" "grey" "black"))
+                   "8 ohms")))
+
+(ert-deftest ignore-extra-colors ()
+  (should (string= (label '("blue" "green" "yellow" "orange"))
+                   "650 kiloohms")))
+
+(provide 'resistor-color-trio-test)
+;;; resistor-color-trio-test.el ends here

exercises/practice/resistor-color-trio/resistor-color-trio.el

@@ -0,0 +1,14 @@
+;;; resistor-color-trio.el --- Resistor Color Trio (exercism)  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;;; Code:
+
+
+(defun label (colors)
+  (error "Delete this S-Expression and write your own implementation"))
+
+
+(provide 'resistor-color-trio)
+;;; resistor-color-trio.el ends here
+