added non trivial examples of closures for str::find

Author: pvdrz

src/liballoc/str.rs

@@ -966,8 +966,8 @@ impl str {
     ///
     /// assert_eq!(s.find(char::is_whitespace), Some(5));
     /// assert_eq!(s.find(char::is_lowercase), Some(1));
-    /// assert_eq!(s.find(|c: char| c.is_whitespace()), Some(5));
-    /// assert_eq!(s.find(|c: char| c.is_lowercase()), Some(1));
+    /// assert_eq!(s.find(|c: char| c.is_whitespace() || c.is_lowercase()), Some(1));
+    /// assert_eq!(s.find(|c: char| (c < 'o') && (c > 'a')), Some(4));
     /// ```
     ///
     /// Not finding the pattern: