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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
commit | 698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch) | |
tree | 173a775858bd501c378080a10dca74132f05bc50 /src/test/ui/traits/monad.rs | |
parent | Initial commit. (diff) | |
download | rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.tar.xz rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.zip |
Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | src/test/ui/traits/monad.rs | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/src/test/ui/traits/monad.rs b/src/test/ui/traits/monad.rs new file mode 100644 index 000000000..5d0612cf8 --- /dev/null +++ b/src/test/ui/traits/monad.rs @@ -0,0 +1,48 @@ +// run-pass + +#![allow(non_camel_case_types)] + + + +trait vec_monad<A> { + fn bind<B, F>(&self, f: F ) -> Vec<B> where F: FnMut(&A) -> Vec<B> ; +} + +impl<A> vec_monad<A> for Vec<A> { + fn bind<B, F>(&self, mut f: F) -> Vec<B> where F: FnMut(&A) -> Vec<B> { + let mut r = Vec::new(); + for elt in self { + r.extend(f(elt)); + } + r + } +} + +trait option_monad<A> { + fn bind<B, F>(&self, f: F) -> Option<B> where F: FnOnce(&A) -> Option<B>; +} + +impl<A> option_monad<A> for Option<A> { + fn bind<B, F>(&self, f: F) -> Option<B> where F: FnOnce(&A) -> Option<B> { + match *self { + Some(ref a) => { f(a) } + None => { None } + } + } +} + +fn transform(x: Option<isize>) -> Option<String> { + x.bind(|n| Some(*n + 1) ).bind(|n| Some(n.to_string()) ) +} + +pub fn main() { + assert_eq!(transform(Some(10)), Some("11".to_string())); + assert_eq!(transform(None), None); + assert_eq!((vec!["hi".to_string()]) + .bind(|x| vec![x.clone(), format!("{}!", x)] ) + .bind(|x| vec![x.clone(), format!("{}?", x)] ), + ["hi".to_string(), + "hi?".to_string(), + "hi!".to_string(), + "hi!?".to_string()]); +} |