std: Add ToResult/IntoResult/AsResult

Author: erickt

src/libstd/either.rs

@@ -54,18 +54,6 @@ impl<L, R> Either<L, R> {
         }
     }
 
-    /// Converts a `Either` to a `Result`
-    ///
-    /// Converts an `Either` type to a `Result` type, making the "right" choice
-    /// an `Ok` result, and the "left" choice a `Err`
-    #[inline]
-    pub fn to_result(self) -> Result<R, L> {
-        match self {
-            Right(r) => result::Ok(r),
-            Left(l) => result::Err(l)
-        }
-    }
-
     /// Checks whether the given value is a `Left`
     #[inline]
     pub fn is_left(&self) -> bool {
@@ -147,6 +135,36 @@ impl<L, R> option::AsOption<R> for Either<L, R> {
     }
 }
 
+impl<L: Clone, R: Clone> result::ToResult<R, L> for Either<L, R> {
+    #[inline]
+    fn to_result(&self)-> result::Result<R, L> {
+        match *self {
+            Left(ref l) => result::Err(l.clone()),
+            Right(ref r) => result::Ok(r.clone()),
+        }
+    }
+}
+
+impl<L, R> result::IntoResult<R, L> for Either<L, R> {
+    #[inline]
+    fn into_result(self)-> result::Result<R, L> {
+        match self {
+            Left(l) => result::Err(l),
+            Right(r) => result::Ok(r),
+        }
+    }
+}
+
+impl<L, R> result::AsResult<R, L> for Either<L, R> {
+    #[inline]
+    fn as_result<'a>(&'a self) -> result::Result<&'a R, &'a L> {
+        match *self {
+            Left(ref l) => result::Err(l),
+            Right(ref r) => result::Ok(r),
+        }
+    }
+}
+
 /// An iterator yielding the `Left` values of its source
 pub type Lefts<L, R, Iter> = FilterMap<'static, Either<L, R>, L, Iter>;
 
@@ -200,6 +218,8 @@ mod tests {
 
     use option::{IntoOption, ToOption, AsOption};
     use option;
+    use result::{IntoResult, ToResult, AsResult};
+    use result;
 
     #[test]
     fn test_either_left() {
@@ -320,4 +340,34 @@ mod tests {
         assert_eq!(right.as_option().unwrap(), &100);
         assert_eq!(left.as_option(), option::None);
     }
+
+    #[test]
+    pub fn test_to_result() {
+        let right: Either<int, int> = Right(100);
+        let left: Either<int, int> = Left(404);
+
+        assert_eq!(right.to_result(), result::Ok(100));
+        assert_eq!(left.to_result(), result::Err(404));
+    }
+
+    #[test]
+    pub fn test_into_result() {
+        let right: Either<int, int> = Right(100);
+        let left: Either<int, int> = Left(404);
+
+        assert_eq!(right.into_result(), result::Ok(100));
+        assert_eq!(left.into_result(), result::Err(404));
+    }
+
+    #[test]
+    pub fn test_as_result() {
+        let right: Either<int, int> = Right(100);
+        let left: Either<int, int> = Left(404);
+
+        let x = 100;
+        assert_eq!(right.as_result(), result::Ok(&x));
+
+        let x = 404;
+        assert_eq!(left.as_result(), result::Err(&x));
+    }
 }

src/libstd/option.rs

@@ -48,6 +48,7 @@ use util;
 use num::Zero;
 use iter;
 use iter::{Iterator, DoubleEndedIterator, ExactSize};
+use result;
 use str::{StrSlice, OwnedStr};
 use to_str::ToStr;
 use clone::DeepClone;
@@ -426,6 +427,26 @@ impl<T> AsOption<T> for Option<T> {
     }
 }
 
+impl<T: Clone> result::ToResult<T, ()> for Option<T> {
+    #[inline]
+    fn to_result(&self) -> result::Result<T, ()> {
+        match *self {
+            Some(ref x) => result::Ok(x.clone()),
+            None => result::Err(()),
+        }
+    }
+}
+
+impl<T> result::IntoResult<T, ()> for Option<T> {
+    #[inline]
+    fn into_result(self) -> result::Result<T, ()> {
+        match self {
+            Some(x) => result::Ok(x),
+            None => result::Err(()),
+        }
+    }
+}
+
 impl<T: Default> Option<T> {
     /// Returns the contained value or default (for this type)
     #[inline]
@@ -508,6 +529,8 @@ impl<A> ExactSize<A> for OptionIterator<A> {}
 #[cfg(test)]
 mod tests {
     use super::*;
+    use result::{IntoResult, ToResult};
+    use result;
     use util;
 
     #[test]
@@ -776,4 +799,22 @@ mod tests {
         assert_eq!(some.as_option().unwrap(), &100);
         assert_eq!(none.as_option(), None);
     }
+
+    #[test]
+    pub fn test_to_result() {
+        let some: Option<int> = Some(100);
+        let none: Option<int> = None;
+
+        assert_eq!(some.to_result(), result::Ok(100));
+        assert_eq!(none.to_result(), result::Err(()));
+    }
+
+    #[test]
+    pub fn test_into_result() {
+        let some: Option<int> = Some(100);
+        let none: Option<int> = None;
+
+        assert_eq!(some.into_result(), result::Ok(100));
+        assert_eq!(none.into_result(), result::Err(()));
+    }
 }

src/libstd/result.rs

@@ -256,6 +256,24 @@ impl<T, E: Clone + ToStr> Result<T, E> {
     }
 }
 
+/// A generic trait for converting a value to a `Result`
+pub trait ToResult<T, E> {
+    /// Convert to the `result` type
+    fn to_result(&self) -> Result<T, E>;
+}
+
+/// A generic trait for converting a value to a `Result`
+pub trait IntoResult<T, E> {
+    /// Convert to the `result` type
+    fn into_result(self) -> Result<T, E>;
+}
+
+/// A generic trait for converting a value to a `Result`
+pub trait AsResult<T, E> {
+    /// Convert to the `result` type
+    fn as_result<'a>(&'a self) -> Result<&'a T, &'a E>;
+}
+
 impl<T: Clone, E> option::ToOption<T> for Result<T, E> {
     #[inline]
     fn to_option(&self)-> Option<T> {
@@ -286,6 +304,26 @@ impl<T, E> option::AsOption<T> for Result<T, E> {
     }
 }
 
+impl<T: Clone, E: Clone> ToResult<T, E> for Result<T, E> {
+    #[inline]
+    fn to_result(&self) -> Result<T, E> { self.clone() }
+}
+
+impl<T, E> IntoResult<T, E> for Result<T, E> {
+    #[inline]
+    fn into_result(self) -> Result<T, E> { self }
+}
+
+impl<T, E> AsResult<T, E> for Result<T, E> {
+    #[inline]
+    fn as_result<'a>(&'a self) -> Result<&'a T, &'a E> {
+        match *self {
+            Ok(ref t) => Ok(t),
+            Err(ref e) => Err(e),
+        }
+    }
+}
+
 #[inline]
 #[allow(missing_doc)]
 pub fn map_opt<T, U: ToStr, V>(o_t: &Option<T>,
@@ -520,4 +558,34 @@ mod tests {
         assert_eq!(ok.as_option().unwrap(), &100);
         assert_eq!(err.as_option(), option::None);
     }
+
+    #[test]
+    pub fn test_to_result() {
+        let ok: Result<int, int> = Ok(100);
+        let err: Result<int, int> = Err(404);
+
+        assert_eq!(ok.to_result(), Ok(100));
+        assert_eq!(err.to_result(), Err(404));
+    }
+
+    #[test]
+    pub fn test_into_result() {
+        let ok: Result<int, int> = Ok(100);
+        let err: Result<int, int> = Err(404);
+
+        assert_eq!(ok.into_result(), Ok(100));
+        assert_eq!(err.into_result(), Err(404));
+    }
+
+    #[test]
+    pub fn test_as_result() {
+        let ok: Result<int, int> = Ok(100);
+        let err: Result<int, int> = Err(404);
+
+        let x = 100;
+        assert_eq!(ok.as_result(), Ok(&x));
+
+        let x = 404;
+        assert_eq!(err.as_result(), Err(&x));
+    }
 }