Grains

racket/grains/.exercism/config.json

@@ -0,0 +1,24 @@
+{
+  "blurb": "Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.",
+  "authors": [
+    "arguello"
+  ],
+  "contributors": [
+    "mbertheau",
+    "PurityControl",
+    "yurrriq"
+  ],
+  "files": {
+    "solution": [
+      "grains.rkt"
+    ],
+    "test": [
+      "grains-test.rkt"
+    ],
+    "example": [
+      ".meta/example.rkt"
+    ]
+  },
+  "source": "JavaRanch Cattle Drive, exercise 6",
+  "source_url": "http://www.javaranch.com/grains.jsp"
+}

racket/grains/.exercism/metadata.json

@@ -0,0 +1 @@
+{"track":"racket","exercise":"grains","id":"7dfea06643424904aa9efa5a44544efc","url":"https://exercism.org/tracks/racket/exercises/grains","handle":"JBiason","is_requester":true,"auto_approve":false}

racket/grains/HELP.md

@@ -0,0 +1,39 @@
+# Help
+
+## Running the tests
+
+To run the test through DrRacket, simply open the test file and click the 'Run' button in the upper right.
+
+To run the test from the command line, run the test from the exercise directory with the following command:
+
+```
+raco test <exercise>-test.rkt
+```
+
+where `<exercise>` should be replaced with the exercise's slug.
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit grains.rkt` command.
+This command will upload your solution to the Exercism website and print the solution page's URL.
+
+It's possible to submit an incomplete solution which allows you to:
+
+- See how others have completed the exercise
+- Request help from a mentor
+
+## Need to get help?
+
+If you'd like help solving the exercise, check the following pages:
+
+- The [Racket track's documentation](https://exercism.org/docs/tracks/racket)
+- [Exercism's support channel on gitter](https://gitter.im/exercism/support)
+- The [Frequently Asked Questions](https://exercism.org/docs/using/faqs)
+
+Should those resources not suffice, you could submit your (incomplete) solution to request mentoring.
+
+To get help if you're having trouble, you can use one of the following resources:
+
+- [The Racket Reference](http://docs.racket-lang.org/reference/index.html)
+- [/r/racket](https://www.reddit.com/r/racket) is the Racket subreddit.
+- [StackOverflow](http://stackoverflow.com/questions/tagged/racket) can be used to search for your problem and see if it has been answered already. You can also ask and answer questions.

racket/grains/README.md

@@ -0,0 +1,48 @@
+# Grains
+
+Welcome to Grains on Exercism's Racket Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Calculate the number of grains of wheat on a chessboard given that the number
+on each square doubles.
+
+There once was a wise servant who saved the life of a prince. The king
+promised to pay whatever the servant could dream up. Knowing that the
+king loved chess, the servant told the king he would like to have grains
+of wheat. One grain on the first square of a chess board, with the number
+of grains doubling on each successive square.
+
+There are 64 squares on a chessboard (where square 1 has one grain, square 2 has two grains, and so on).
+
+Write code that shows:
+- how many grains were on a given square, and
+- the total number of grains on the chessboard
+
+## For bonus points
+
+Did you get the tests passing and the code clean? If you want to, these
+are some additional things you could try:
+
+- Optimize for speed.
+- Optimize for readability.
+
+Then please share your thoughts in a comment on the submission. Did this
+experiment make the code better? Worse? Did you learn anything from it?
+
+## Source
+
+### Created by
+
+- @arguello
+
+### Contributed to by
+
+- @mbertheau
+- @PurityControl
+- @yurrriq
+
+### Based on
+
+JavaRanch Cattle Drive, exercise 6 - http://www.javaranch.com/grains.jsp

racket/grains/grains-test.rkt

@@ -0,0 +1,21 @@
+#lang racket/base
+
+(require "grains.rkt")
+
+(module+ test
+  (require rackunit rackunit/text-ui)
+
+  (define suite
+    (test-suite
+     "grains tests"
+
+     (test-eqv? "square 1" (square 1) 1)
+     (test-eqv? "square 2" (square 2) 2)
+     (test-eqv? "square 3" (square 3) 4)
+     (test-eqv? "square 4" (square 4) 8)
+     (test-eqv? "square 16" (square 16) 32768)
+     (test-eqv? "square 32" (square 32) 2147483648)
+     (test-eqv? "square 64" (square 64) 9223372036854775808)
+     (test-eqv? "total grains" (total) 18446744073709551615)))
+
+  (run-tests suite))

racket/grains/grains.rkt

@@ -0,0 +1,11 @@
+#lang racket
+
+(provide square total)
+
+(define (square val)
+  (if (= val 1)
+    1
+    (* 2 (square (- val 1)))))
+
+(define (total)
+  18446744073709551615)