Rust - Solved Square

rust/grains/.gitignore

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+# Generated by Cargo
+# will have compiled files and executables
+/target/
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here http://doc.crates.io/guide.html#cargotoml-vs-cargolock
+Cargo.lock

rust/grains/Cargo.toml

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+[package]
+name = "grains"
+version = "0.0.0"

rust/grains/README.md

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+# Grains
+
+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. Two grains on
+the next. Four on the third, and so on.
+
+There are 64 squares on a chessboard.
+
+Write code that shows:
+- how many grains were on each square, and
+- the total number of grains
+
+
+## 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?
+
+## Rust Installation
+
+Refer to the [exercism help page][help-page] for Rust installation and learning
+resources.
+
+## Writing the Code
+
+Execute the tests with:
+
+```bash
+$ cargo test
+```
+
+All but the first test have been ignored.  After you get the first test to
+pass, remove the ignore flag (`#[ignore]`) from the next test and get the tests
+to pass again.  The test file is located in the `tests` directory.   You can
+also remove the ignore flag from all the tests to get them to run all at once
+if you wish.
+
+Make sure to read the [Crates and Modules](https://doc.rust-lang.org/stable/book/crates-and-modules.html) chapter if you
+haven't already, it will help you with organizing your files.
+
+## Feedback, Issues, Pull Requests
+
+The [exercism/xrust](https://github.com/exercism/xrust) repository on GitHub is the home for all of the Rust exercises. If you have feedback about an exercise, or want to help implement new exercises, head over there and create an issue. Members of the [rust track team](https://github.com/orgs/exercism/teams/rust) are happy to help!
+
+If you want to know more about Exercism, take a look at the [contribution guide](https://github.com/exercism/x-common/blob/master/CONTRIBUTING.md).
+
+[help-page]: http://exercism.io/languages/rust
+[crates-and-modules]: http://doc.rust-lang.org/stable/book/crates-and-modules.html
+
+## Source
+
+JavaRanch Cattle Drive, exercise 6 [http://www.javaranch.com/grains.jsp](http://www.javaranch.com/grains.jsp)
+
+## Submitting Incomplete Problems
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
+

rust/grains/src/lib.rs

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+pub fn square(s: u32) -> u64 {
+    if (s > 0) && (s < 65){
+        return 2u64.pow(s-1);
+    }
+    else{
+        panic!("Square must be between 1 and 64");
+    }
+}
+
+pub fn total() -> u64 {
+    let mut sum: u64 = 0;
+    for i in 1..65{
+        sum += square(i);
+    }
+    return sum;
+}

rust/grains/tests/grains.rs

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+extern crate grains;
+
+#[test]
+fn square_one() {
+    assert_eq!(grains::square(1), 1);
+}
+
+#[test]
+fn square_two() {
+    assert_eq!(grains::square(2), 2);
+}
+
+#[test]
+fn square_three() {
+    assert_eq!(grains::square(3), 4);
+}
+
+#[test]
+fn square_four() {
+    assert_eq!(grains::square(4), 8);
+}
+
+#[test]
+fn square_sixteen() {
+    assert_eq!(grains::square(16), 32_768);
+}
+
+#[test]
+fn square_thirty_two() {
+    assert_eq!(grains::square(32), 2_147_483_648);
+}
+
+#[test]
+fn square_sixty_four() {
+    assert_eq!(grains::square(64), 9_223_372_036_854_775_808);
+}
+
+#[test]
+#[should_panic(expected = "Square must be between 1 and 64")]
+fn square_zero_panics() {
+    grains::square(0);
+}
+
+#[test]
+#[should_panic(expected = "Square must be between 1 and 64")]
+fn square_sixty_five_panics() {
+    grains::square(65);
+}
+
+#[test]
+fn total_sums_all_squares() {
+    assert_eq!(grains::total(), 18_446_744_073_709_551_615);
+    grains::total();
+}