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rustlings-exercises-completed/exercises/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.
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// Execute `rustlings hint as_ref_mut` or use the `hint` watch subcommand for a hint.
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// Obtain the number of bytes (not characters) in the given argument.
// TODO: Add the AsRef trait appropriately as a trait bound.
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fn byte_counter<T: AsRef<str>>(arg: T) -> usize {
arg.as_ref().as_bytes().len()
}
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// Obtain the number of characters (not bytes) in the given argument.
// TODO: Add the AsRef trait appropriately as a trait bound.
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fn char_counter<T: AsRef<str>>(arg: T) -> usize {
arg.as_ref().chars().count()
}
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// Squares a number using as_mut().
// TODO: Add the appropriate trait bound.
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fn num_sq<T: AsMut<u32> + AsRef<u32>>(arg: &mut T) {
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// TODO: Implement the function body.
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*arg.as_mut() = arg.as_ref().pow(2);
}
#[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));
}
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#[test]
fn mult_box() {
let mut num: Box<u32> = Box::new(3);
num_sq(&mut num);
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assert_eq!(*num, 9);
}
}