added min_and_max function

src/main.rs

@@ -41,6 +41,37 @@ fn _get_static_str() -> &'static str {
     "hello"
 }
 
+#[derive(Debug, PartialEq)]
+struct EmptyListError;
+
+// implementing Error for my error to satisfy Box<dyn std::error::Error>
+// not needed ATM
+// impl std::error::Error for EmptyListError {}
+// impl std::fmt::Display for EmptyListError {
+//     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+//         write!(f, "list must not be empty")
+//     }
+// }
+
+// Result<...,Box<dyn std::error::Error>> is overkill
+// this is intuitive enough for caller error detection 
+fn min_and_max(list: &[u32]) -> Result<(u32, u32), EmptyListError> {
+    if list.is_empty() {
+        return Err(EmptyListError);
+    }
+    let mut min:u32 = 100;
+    let mut max:u32 = 0;
+    for i in list {
+        if *i > max {
+            max = *i;
+        } 
+        if *i < min {
+            min = *i;
+        }
+    } 
+    Ok((min,max))
+}
+
 fn main() {
     println!("Hello, world!");
     fmt_debug::test_report();
@@ -80,4 +111,15 @@ fn main() {
     let _s6 = String::from(s_lit); //underlying data copied to heap
 
     // todo: Cow
+    println!("Learning Rust");
+
+    let empty = [];
+    let empty_min_and_max = min_and_max(&empty);
+    assert!(empty_min_and_max.as_ref().is_err());
+    assert!(*(empty_min_and_max.as_ref().err().unwrap()) == EmptyListError);
+
+    let l = [ 1, 2, 10, 100, 50, 75, 36, 21];
+    let l_min_and_max = min_and_max(&l);
+    assert!(l_min_and_max.as_ref().unwrap().0 == 1);
+    assert!(l_min_and_max.as_ref().unwrap().1 == 100);
 }