as_ref_mut.rs (1677B)
1 // AsRef and AsMut allow for cheap reference-to-reference conversions. Read more 2 // about them at https://doc.rust-lang.org/std/convert/trait.AsRef.html and 3 // https://doc.rust-lang.org/std/convert/trait.AsMut.html, respectively. 4 5 // Obtain the number of bytes (not characters) in the given argument 6 // (`.len()` returns the number of bytes in a string). 7 // TODO: Add the `AsRef` trait appropriately as a trait bound. 8 fn byte_counter<T>(arg: T) -> usize { 9 arg.as_ref().len() 10 } 11 12 // Obtain the number of characters (not bytes) in the given argument. 13 // TODO: Add the `AsRef` trait appropriately as a trait bound. 14 fn char_counter<T>(arg: T) -> usize { 15 arg.as_ref().chars().count() 16 } 17 18 // Squares a number using `as_mut()`. 19 // TODO: Add the appropriate trait bound. 20 fn num_sq<T>(arg: &mut T) { 21 // TODO: Implement the function body. 22 } 23 24 fn main() { 25 // You can optionally experiment here. 26 } 27 28 #[cfg(test)] 29 mod tests { 30 use super::*; 31 32 #[test] 33 fn different_counts() { 34 let s = "Café au lait"; 35 assert_ne!(char_counter(s), byte_counter(s)); 36 } 37 38 #[test] 39 fn same_counts() { 40 let s = "Cafe au lait"; 41 assert_eq!(char_counter(s), byte_counter(s)); 42 } 43 44 #[test] 45 fn different_counts_using_string() { 46 let s = String::from("Café au lait"); 47 assert_ne!(char_counter(s.clone()), byte_counter(s)); 48 } 49 50 #[test] 51 fn same_counts_using_string() { 52 let s = String::from("Cafe au lait"); 53 assert_eq!(char_counter(s.clone()), byte_counter(s)); 54 } 55 56 #[test] 57 fn mut_box() { 58 let mut num: Box<u32> = Box::new(3); 59 num_sq(&mut num); 60 assert_eq!(*num, 9); 61 } 62 }