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rustlings/solutions/23_conversions/as_ref_mut.rs

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// 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.
fn byte_counter<T: AsRef<str>>(arg: T) -> usize {
arg.as_ref().as_bytes().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();
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*arg *= *arg;
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}
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);
}
}