Merge pull request exercism#84 from cpaulbond/master

Added armstrong numbers exercises.

config.json

@@ -176,6 +176,14 @@
       "topics": null,
       "unlocked_by": null,
       "uuid": "a252e137-8a63-4f26-b119-7264f12a257a"
+    },
+    {
+      "core": false,
+      "difficulty": 1,
+      "slug": "armstrong-numbers",
+      "topics": null,
+      "unlocked_by": null,
+      "uuid": "059141f0-f28d-4d10-a03a-7852dbfc2d2e"
     }
   ],
   "foregone": [],

exercises/armstrong-numbers/README.md

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+## Armstrong numbers
+
+An [Armstrong number](https://en.wikipedia.org/wiki/Narcissistic_number) is a number that is the sum of its own digits each raised to the power of the number of digits.
+
+For example:
+
+- 9 is an Armstrong number, because `9 = 9^1 = 9`
+- 10 is *not* an Armstrong number, because `10 != 1^2 + 0^2 = 1`
+- 153 is an Armstrong number, because: `153 = 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153`
+- 154 is *not* an Armstrong number, because: `154 != 1^3 + 5^3 + 4^3 = 1 + 125 + 64 = 190`
+
+Write some code to determine whether a number is an Armstrong number.
+
+## Source
+
+See more at [wikipedia](https://en.wikipedia.org/wiki/Narcissistic_number)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

exercises/armstrong-numbers/armstrong-numbers-test.el

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+;;; armstrong-numbers-test.el --- Tests for armstrong-numbers (exercism)
+
+;;; Commentary:
+
+;;; Code:
+
+(load-file "armstrong-numbers.el")
+
+(ert-deftest armstrong-number-5 ()
+  "Single digit numbers are Armstrong numbers"
+  (should (armstrong-p 5)))
+
+(ert-deftest not-armstrong-number-10 ()
+  "There are no 2 digit Armstrong numbers"
+  (should (not (armstrong-p 10))))
+
+(ert-deftest armstrong-number-153 ()
+  "Three digit number that should an Armstrong number"
+  (should (armstrong-p 153)))
+
+(ert-deftest not-armstrong-number-100 ()
+  "Three digit number that should an Armstrong number"
+  (should (not (armstrong-p 100))))
+
+(ert-deftest armstrong-number-9474 ()
+  "Four digit number that should an Armstrong number"
+  (should (armstrong-p 9474)))
+
+(ert-deftest not-armstrong-number-9475 ()
+  "Four digit number that should not an Armstrong number"
+  (should (not (armstrong-p 9476))))
+
+(ert-deftest armstrong-number-9926315 ()
+  "Seven digit number that should an Armstrong number"
+  (should (armstrong-p 9926315)))
+
+(ert-deftest not-armstrong-number-9926314 ()
+  "Seven digit number that should not an Armstrong number"
+  (should (not (armstrong-p 9926314))))
+
+;;; armstrong-numbers-test.el ends here

exercises/armstrong-numbers/armstrong-numbers.el

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+;;; armstrong-numbers.el --- armstrong-numbers Exercise (exercism)
+
+;;; Commentary:
+
+;;; Code:
+
+(provide 'armstrong-numbers)
+;;; armstrong-numbers.el ends here

exercises/armstrong-numbers/example.el

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+;;; armstrong-numbers.el --- armstrong-numbers Exercise (exercism)
+
+;;; Commentary:
+
+;;; Code:
+
+(defun armstrong-p (n)
+  (let* ((digits (mapcar #'(lambda (d) (- d ?0)) (string-to-list (int-to-string n))))
+	 (p (length digits)))
+    (= n (apply '+ (mapcar #'(lambda (d) (expt d p)) digits)))))
+
+(provide 'armstrong-numbers)
+;;; armstrong-numbers.el ends here