Add ok-or-else extension

Extracted from imag, where the source is LGPL2.0,  but I am the author
and hereby relicense this piece of code with MPL 2.0 for the resiter
crate repository.

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>

2 files changed, 74 insertions, 0 deletions

diff --git a/src/lib.rs b/src/lib.rs
index ff4ecc3..e9ba2f3 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -201,6 +201,7 @@ pub mod filter_map;
 pub mod flat_map;
 pub mod flatten;
 pub mod map;
+pub mod ok_or_else;
 pub mod oks;
 pub mod onerr;
 pub mod onok;
@@ -216,6 +217,7 @@ pub use filter_map::FilterMap;
 pub use flat_map::FlatMap;
 pub use flatten::Flatten;
 pub use map::Map;
+pub use ok_or_else::{ResultOptionExt, IterInnerOkOrElse};
 pub use oks::GetOks;
 pub use onerr::OnErrDo;
 pub use onok::OnOkDo;
diff --git a/src/ok_or_else.rs b/src/ok_or_else.rs
new file mode 100644
index 0000000..c071af9
--- /dev/null
+++ b/src/ok_or_else.rs
@@ -0,0 +1,72 @@
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+//
+
+/// Extension trait for doing `Result<Option<T>, E>  ->  Result<T, E>`
+pub trait ResultOptionExt<T, E, F>
+    where T: Sized,
+          E: Sized,
+          F: FnOnce() -> E
+{
+    fn inner_ok_or_else(self, f: F) -> Result<T, E>;
+}
+
+impl<T, E, F> ResultOptionExt<T, E, F> for Result<Option<T>, E>
+    where T: Sized,
+          E: Sized,
+          F: FnOnce() -> E
+{
+    fn inner_ok_or_else(self, f: F) -> Result<T, E> {
+        self.and_then(|opt| opt.ok_or_else(f))
+    }
+}
+
+
+
+/// Extension trait for doing
+///
+/// ```ignore
+///     Iterator<Item = Result<Option<T>, E>>  ->  Iterator<Item = Result<T, E>>
+/// ```
+///
+pub trait IterInnerOkOrElse<T, E, F>
+    where T: Sized,
+          E: Sized,
+          Self: Iterator<Item = Result<Option<T>, E>> + Sized,
+          F: Fn() -> E,
+{
+    fn map_inner_ok_or_else(self, f: F) -> IterInnerOkOrElseImpl<Self, T, E, F>;
+}
+
+pub struct IterInnerOkOrElseImpl<I, T, E, F>(I, F)
+    where I: Iterator<Item = Result<Option<T>, E>> + Sized,
+          T: Sized,
+          E: Sized,
+          F: Fn() -> E;
+
+impl<I, T, E, F> IterInnerOkOrElse<T, E, F> for I
+    where I: Iterator<Item = Result<Option<T>, E>> + Sized,
+          T: Sized,
+          E: Sized,
+          F: Fn() -> E,
+{
+    fn map_inner_ok_or_else(self, f: F) -> IterInnerOkOrElseImpl<I, T, E, F> {
+        IterInnerOkOrElseImpl(self, f)
+    }
+}
+
+impl<I, T, E, F> Iterator for IterInnerOkOrElseImpl<I, T, E, F>
+    where I: Iterator<Item = Result<Option<T>, E>> + Sized,
+          T: Sized,
+          E: Sized,
+          F: Fn() -> E,
+{
+    type Item = Result<T, E>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.0.next().map(|e| e.and_then(|opt| opt.ok_or_else(|| (self.1)())))
+    }
+}
+