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| author | Hunter Kvalevog <hunter@kvog.sh> | 2026-10-02 21:53:51 -0500 |
|---|---|---|
| committer | Hunter Kvalevog <hunter@kvog.sh> | 2026-10-02 21:53:51 -0500 |
| commit | 4dfc11d74ab02ac5765ae5d08fb750c91f4744b4 (patch) | |
| tree | 17ba62056d6b691dd0217b0e8f1b3a5826dce0f6 /rustlings/solutions/19_smart_pointers/cow1.rs | |
| parent | 02d8f1c62896576e1266553a56980eddbc2a88d7 (diff) | |
rustlings: move to rust/
Diffstat (limited to 'rustlings/solutions/19_smart_pointers/cow1.rs')
| -rw-r--r-- | rustlings/solutions/19_smart_pointers/cow1.rs | 69 |
1 files changed, 0 insertions, 69 deletions
diff --git a/rustlings/solutions/19_smart_pointers/cow1.rs b/rustlings/solutions/19_smart_pointers/cow1.rs deleted file mode 100644 index 461143b..0000000 --- a/rustlings/solutions/19_smart_pointers/cow1.rs +++ /dev/null @@ -1,69 +0,0 @@ -// This exercise explores the `Cow` (Clone-On-Write) smart pointer. It can -// enclose and provide immutable access to borrowed data and clone the data -// lazily when mutation or ownership is required. The type is designed to work -// with general borrowed data via the `Borrow` trait. - -use std::borrow::Cow; - -fn abs_all(input: &mut Cow<[i32]>) { - for ind in 0..input.len() { - let value = input[ind]; - if value < 0 { - // Clones into a vector if not already owned. - input.to_mut()[ind] = -value; - } - } -} - -fn main() { - // You can optionally experiment here. -} - -#[cfg(test)] -mod tests { - use super::*; - - #[test] - fn reference_mutation() { - // Clone occurs because `input` needs to be mutated. - let vec = vec![-1, 0, 1]; - let mut input = Cow::from(&vec); - abs_all(&mut input); - assert!(matches!(input, Cow::Owned(_))); - } - - #[test] - fn reference_no_mutation() { - // No clone occurs because `input` doesn't need to be mutated. - let vec = vec![0, 1, 2]; - let mut input = Cow::from(&vec); - abs_all(&mut input); - assert!(matches!(input, Cow::Borrowed(_))); - // ^^^^^^^^^^^^^^^^ - } - - #[test] - fn owned_no_mutation() { - // We can also pass `vec` without `&` so `Cow` owns it directly. In this - // case, no mutation occurs (all numbers are already absolute) and thus - // also no clone. But the result is still owned because it was never - // borrowed or mutated. - let vec = vec![0, 1, 2]; - let mut input = Cow::from(vec); - abs_all(&mut input); - assert!(matches!(input, Cow::Owned(_))); - // ^^^^^^^^^^^^^ - } - - #[test] - fn owned_mutation() { - // Of course this is also the case if a mutation does occur (not all - // numbers are absolute). In this case, the call to `to_mut()` in the - // `abs_all` function returns a reference to the same data as before. - let vec = vec![-1, 0, 1]; - let mut input = Cow::from(vec); - abs_all(&mut input); - assert!(matches!(input, Cow::Owned(_))); - // ^^^^^^^^^^^^^ - } -} |