mirror of https://github.com/rust-lang/rustlings
Incorporate ConnyOnny's iterator exercise!
- Deciding not to have solutions in the tree right now, until I figure out a more general way to handle that. - The assertions work really great as tests, actually! - Simplifying a few of the side points-- I think they deserve their own exercises :)pull/43/head
Carol (Nichols || Goulding)
8 years ago
parent
d0f4ee1b39
commit
4bf727cbf7
@ -1,164 +0,0 @@
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// 1. Complete the divide function
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// 2. Uncomment and complete the second part of the main function
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// For part 2 there is a minor hint around line 100 and a major hint around line 128
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// There are some final comments for when you are done around line 150
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// Have fun :-)
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// In production code you would not derive Debug, but implement it manually to get a better error message.
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#[derive(Debug,PartialEq,Eq)]
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enum DivisionError {
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NotDivisible(NotDivisibleError),
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DivideByZero,
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}
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#[derive(Debug,PartialEq,Eq)]
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struct NotDivisibleError {
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divident: i32,
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divisor: i32,
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}
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// This function calculates a/b if a is divisible by b.
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// Otherwise it returns a suitable error.
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fn divide(a: i32, b: i32) -> Result<i32,DivisionError> {
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}
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#[allow(dead_code)]
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enum OperationMode {
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ListOfResults,
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ResultWithList,
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}
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fn main() {
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// These asserts check that your `divide` function works.
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// In production code these would be tests
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assert_eq!(divide(81,9),Ok(9));
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assert_eq!(divide(81,6),Err(DivisionError::NotDivisible(NotDivisibleError{divident:81,divisor:6})));
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assert_eq!(divide(81,0),Err(DivisionError::DivideByZero));
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assert_eq!(divide(0,81),Ok(0));
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println!("Your divide function seems to work! Good Job.");
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/* Second part of main. Uncomment to continue.
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// Don't change these numbers. It will break the assertions later in the code.
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let numbers = vec![27,297,38502,81];
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let division_results = // Do not convert the results into a Vec yet. Leave them iterable for now.
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let operation_mode = OperationMode::ResultWithList;
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match operation_mode {
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OperationMode::ResultWithList => {
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println!("{:?}", x);
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assert_eq!(format!("{:?}",x), "Ok([1, 11, 1426, 3])");
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},
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OperationMode::ListOfResults => {
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println!("{:?}", x);
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assert_eq!(format!("{:?}",x), "[Ok(1), Ok(11), Ok(1426), Ok(3)]");
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},
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}
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*/
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}
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// Minor hint: In each of the two cases in the match in main, you can create x with either a 'turbofish' or by hinting the type of x to the compiler. You may try both.
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// Major hint: Have a look at the Iter trait and at the explanation of its collect function. Especially the part about Result is interesting.
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// Final comments
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// When you call the function `print_result_with_list` with x, you don't need any type annotations on x anymore.
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// The compiler can infer its type through the function's input type.
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#[allow(dead_code)]
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// Don't use this function to solve the exercise
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fn print_result_with_list(r: Result<Vec<i32>,DivisionError>) {
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// side quest: why is there no semicolon in this function?
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match r {
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Ok(v) => println!("All numbers were successfully divided: {:?}", v),
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Err(e) => match e {
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DivisionError::NotDivisible(nde) => println!("Failed to divide {} by {}: Not divisible!", nde.divident, nde.divisor),
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DivisionError::DivideByZero => println!("Can't divide by zero"),
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},
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};
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}
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@ -1,68 +0,0 @@
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// In production code you would not derive Debug, but implement it manually to get a better error message.
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#[derive(Debug,PartialEq,Eq)]
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enum DivisionError {
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NotDivisible(NotDivisibleError),
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DivideByZero,
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}
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#[derive(Debug,PartialEq,Eq)]
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struct NotDivisibleError {
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divident: i32,
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divisor: i32,
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}
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// This function calculates a/b if a is divisible by b.
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// Otherwise it returns a suitable error.
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fn divide(a: i32, b: i32) -> Result<i32,DivisionError> {
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if b == 0 {
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return Err(DivisionError::DivideByZero);
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}
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match a % b {
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0 => Ok(a/b),
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_ => Err(DivisionError::NotDivisible(NotDivisibleError{divident:a, divisor:b})),
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}
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}
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#[allow(dead_code)]
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enum OperationMode {
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ListOfResults,
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ResultWithList,
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}
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#[allow(dead_code)]
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fn print_result_with_list(r: Result<Vec<i32>,DivisionError>) {
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// side quest: why is there no semicolon in this function?
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match r {
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Ok(v) => println!("All numbers were successfully divided: {:?}", v),
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Err(e) => match e {
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DivisionError::NotDivisible(nde) => println!("Failed to divide {} by {}: Not divisible!", nde.divident, nde.divisor),
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DivisionError::DivideByZero => println!("Can't divide by zero"),
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},
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};
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}
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fn main() {
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// These asserts check that your `divide` function works.
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// In production code these would be tests
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assert_eq!(divide(81,9),Ok(9));
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assert_eq!(divide(81,6),Err(DivisionError::NotDivisible(NotDivisibleError{divident:81,divisor:6})));
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assert_eq!(divide(81,0),Err(DivisionError::DivideByZero));
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println!("Your divide function seems to work! Good Job.");
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// Don't change these numbers. It will break the assertions later in the code.
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let numbers = vec![27,297,38502,81];
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let numbers_iterator = numbers.into_iter();
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let division_results = numbers_iterator.map(|n| divide(n, 27));
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let operation_mode = OperationMode::ResultWithList; // you may change this
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match operation_mode {
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OperationMode::ResultWithList => {
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let x : Result<Vec<_>,_> = division_results.collect();
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//print_result_with_list(x);
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assert_eq!(format!("{:?}",x), "Ok([1, 11, 1426, 3])");
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},
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OperationMode::ListOfResults => {
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let x : Vec<_> = division_results.collect();
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println!("{:?}", x);
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assert_eq!(format!("{:?}",x), "[Ok(1), Ok(11), Ok(1426), Ok(3)]");
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},
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}
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}
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@ -0,0 +1,144 @@
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// This is a bigger exercise than most of the others! You can do it!
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// Here is your mission, should you choose to accept it:
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// 1. Complete the divide function to get the first four tests to pass
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// 2. Uncomment the last two tests and get them to pass by filling in
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// values for `x` using `division_results`.
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// Scroll down for a minor hint for part 2, and scroll down further for
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// a major hint.
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// Have fun :-)
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#[derive(Debug, PartialEq, Eq)]
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pub enum DivisionError {
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NotDivisible(NotDivisibleError),
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DivideByZero,
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}
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#[derive(Debug, PartialEq, Eq)]
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pub struct NotDivisibleError {
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dividend: i32,
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divisor: i32,
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}
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// This function should calculate `a` divided by `b` if `a` is
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// evenly divisible by b.
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// Otherwise, it should return a suitable error.
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pub fn divide(a: i32, b: i32) -> Result<i32, DivisionError> {
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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// Tests that verify your `divide` function implementation
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#[test]
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fn test_success() {
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assert_eq!(divide(81, 9), Ok(9));
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}
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#[test]
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fn test_not_divisible() {
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assert_eq!(
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divide(81, 6),
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Err(DivisionError::NotDivisible(NotDivisibleError{
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dividend: 81,
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divisor: 6
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}))
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);
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}
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#[test]
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fn test_divide_by_0() {
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assert_eq!(divide(81, 0), Err(DivisionError::DivideByZero));
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}
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#[test]
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fn test_divide_0_by_something() {
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assert_eq!(divide(0, 81), Ok(0));
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}
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// Iterator exercises using your `divide` function
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/*
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#[test]
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fn result_with_list() {
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let numbers = vec![27, 297, 38502, 81];
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let division_results = numbers.into_iter().map(|n| divide(n, 27));
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let x //... Fill in here!
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assert_eq!(format!("{:?}", x), "Ok([1, 11, 1426, 3])");
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}
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#[test]
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fn list_of_results() {
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let numbers = vec![27, 297, 38502, 81];
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let division_results = numbers.into_iter().map(|n| divide(n, 27));
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let x //... Fill in here!
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assert_eq!(format!("{:?}", x), "[Ok(1), Ok(11), Ok(1426), Ok(3)]");
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}
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*/
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}
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// Minor hint: In each of the two cases in the match in main, you can create x with either a 'turbofish' or by hinting the type of x to the compiler. You may try both.
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// Major hint: Have a look at the Iter trait and at the explanation of its collect function. Especially the part about Result is interesting.
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