added exercise iterator1 and its solution

This commit is contained in:
Constantin Berhard 2016-04-14 12:16:04 +02:00
parent 203b9167ea
commit d989bbebd0
2 changed files with 196 additions and 0 deletions

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// 1. Complete the divide function
// 2. Uncomment and complete the second part of the main function
// For part 2 there is a minor hint around line 100 and a major hint around line 128
// There is a minor side quest in the "print_result_with_list" function
// Have fun :-)
// In production code you would not derive Debug, but implement it manually to get a better error message.
#[derive(Debug,PartialEq,Eq)]
enum DivisionError {
NotDivisible(NotDivisibleError),
DivideByZero,
}
#[derive(Debug,PartialEq,Eq)]
struct NotDivisibleError {
divident: i32,
divisor: i32,
}
// This function calculates a/b if a is divisible by b.
// Otherwise it returns a suitable error.
fn divide(a: i32, b: i32) -> Result<i32,DivisionError> {
if b == 0 {
}
match a % b {
}
}
// these print functions exist, so you have to satisfy their input types in the main function
fn print_list_of_results(l: Vec<Result<i32,DivisionError>>) {
println!("{:?}", l);
}
fn print_result_with_list(r: Result<Vec<i32>,DivisionError>) {
// side quest: why is there no semicolon in this function?
match r {
Ok(v) => println!("All numbers were successfully divided: {:?}", v),
Err(e) => match e {
DivisionError::NotDivisible(nde) => println!("Failed to divide {} by {}: Not divisible!", nde.divident, nde.divisor),
DivisionError::DivideByZero => println!("Can't divide by zero"),
},
};
}
#[allow(dead_code)]
enum OperationMode {
ListOfResults,
ResultWithList,
}
fn main() {
// These asserts check that your `divide` function works.
// In production code these would be tests
assert_eq!(divide(81,9),Ok(9));
assert_eq!(divide(81,6),Err(DivisionError::NotDivisible(NotDivisibleError{divident:81,divisor:6})));
assert_eq!(divide(81,0),Err(DivisionError::DivideByZero));
println!("Your divide function seems to work! Good Job.");
/* Second part of main. Uncomment to continue.
let numbers = vec![27,297,38502,81];
let division_results = // Do not convert the results into a Vec yet. Leave them iterable for now.
let operation_mode = OperationMode::ResultWithList;
match operation_mode {
OperationMode::ResultWithList => {
print_result_with_list(x);
},
OperationMode::ListOfResults => {
print_list_of_results(x);
},
} */
}
// 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.
// 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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// In production code you would not derive Debug, but implement it manually to get a better error message.
#[derive(Debug,PartialEq,Eq)]
enum DivisionError {
NotDivisible(NotDivisibleError),
DivideByZero,
}
#[derive(Debug,PartialEq,Eq)]
struct NotDivisibleError {
divident: i32,
divisor: i32,
}
// This function calculates a/b if a is divisible by b.
// Otherwise it returns a suitable error.
fn divide(a: i32, b: i32) -> Result<i32,DivisionError> {
if b == 0 {
return Err(DivisionError::DivideByZero);
}
match a % b {
0 => Ok(a/b),
_ => Err(DivisionError::NotDivisible(NotDivisibleError{divident:a, divisor:b})),
}
}
// these print functions exist, so you have to satisfy their input types in the main function
fn print_list_of_results(l: Vec<Result<i32,DivisionError>>) {
println!("{:?}", l);
}
fn print_result_with_list(r: Result<Vec<i32>,DivisionError>) {
// side quest: why is there no semicolon in this function?
match r {
Ok(v) => println!("All numbers were successfully divided: {:?}", v),
Err(e) => match e {
DivisionError::NotDivisible(nde) => println!("Failed to divide {} by {}: Not divisible!", nde.divident, nde.divisor),
DivisionError::DivideByZero => println!("Can't divide by zero"),
},
};
}
#[allow(dead_code)]
enum OperationMode {
ListOfResults,
ResultWithList,
}
fn main() {
// These asserts check that your `divide` function works.
// In production code these would be tests
assert_eq!(divide(81,9),Ok(9));
assert_eq!(divide(81,6),Err(DivisionError::NotDivisible(NotDivisibleError{divident:81,divisor:6})));
assert_eq!(divide(81,0),Err(DivisionError::DivideByZero));
println!("Your divide function seems to work! Good Job.");
let numbers = vec![27,297,38502,81];
let numbers_iterator = numbers.into_iter();
let division_results = numbers_iterator.map(|n| divide(n, 27));
let operation_mode = OperationMode::ResultWithList; // you may change this
match operation_mode {
OperationMode::ResultWithList => {
let x : Result<Vec<_>,_> = division_results.collect();
print_result_with_list(x);
},
OperationMode::ListOfResults => {
let x : Vec<_> = division_results.collect();
print_list_of_results(x);
},
}
}