// AsRef and AsMut allow for cheap reference-to-reference conversions. Read more // about them at https://doc.rust-lang.org/std/convert/trait.AsRef.html and // https://doc.rust-lang.org/std/convert/trait.AsMut.html, respectively. // Obtain the number of bytes (not characters) in the given argument // (`.len()` returns the number of bytes in a string). fn byte_counter<T: AsRef<str>>(arg: T) -> usize { arg.as_ref().len() } // Obtain the number of characters (not bytes) in the given argument. fn char_counter<T: AsRef<str>>(arg: T) -> usize { arg.as_ref().chars().count() } // Squares a number using `as_mut()`. fn num_sq<T: AsMut<u32>>(arg: &mut T) { let arg = arg.as_mut(); *arg *= *arg; } fn main() { // You can optionally experiment here. } #[cfg(test)] mod tests { use super::*; #[test] fn different_counts() { let s = "Café au lait"; assert_ne!(char_counter(s), byte_counter(s)); } #[test] fn same_counts() { let s = "Cafe au lait"; assert_eq!(char_counter(s), byte_counter(s)); } #[test] fn different_counts_using_string() { let s = String::from("Café au lait"); assert_ne!(char_counter(s.clone()), byte_counter(s)); } #[test] fn same_counts_using_string() { let s = String::from("Cafe au lait"); assert_eq!(char_counter(s.clone()), byte_counter(s)); } #[test] fn mut_box() { let mut num: Box<u32> = Box::new(3); num_sq(&mut num); assert_eq!(*num, 9); } }