updated custom_sum, phantom, sum examples

Author: BartMassey

README.md

@@ -22,8 +22,8 @@ in a controlled repository now.
 * `result/`: example of defining and using `Result`
 * `top.rs`: top-n list example using generics
 * `sum.rs`: generic iterator sum example
+* `custom_sum.rs`: sum example with custom `Sum` type
 * `addy.rs`: trait def/impl example
 * `bno-salad.rs`: trait salad example from Blandy and Orendorff
 * `matmul.rs`: example of overloading multiplication for matrices
-* `custom_sum.rs`: sum example with custom `Sum` type
 * `phantom.rs`: phantom type example

custom_sum.rs

@@ -12,6 +12,6 @@ impl Sum<MyU8> for u16 {
 }
 
 fn main() {
-    let s = vec![MyU8(1), MyU8(2), MyU8(3)].into_iter().sum::<u16>();
+    let s: u16 = vec![MyU8(1), MyU8(2), MyU8(3)].into_iter().sum();
     println!("{}", s);
 }

phantom.rs

@@ -10,7 +10,7 @@ unsafe fn hasher(start: *const u8, nbytes: usize) -> u128 {
     let mut result: u128 = 0;
     for i in 0..nbytes {
         let b = *start.offset(i as isize);
-        result += b as u128;
+        result = result.wrapping_add(b as u128);
     }
     result
 }
@@ -26,9 +26,9 @@ impl<T> Hash<T> {
 }
 
 fn main() {
-    let h1 = Hash::hash((0i32,));
+    let h1 = Hash::hash((0i32, 1i32));
     println!("{:?}", h1);
-    let h2 = Hash::hash((0u32,));
+    let h2 = Hash::hash(1u64);
     println!("{:?}", h2);
     // Can't even compare these, since they are of
     // different type.

sum.rs

@@ -1,4 +1,4 @@
 fn main() {
-    let s = vec![1u8, 2, 3].into_iter().sum();
+    let s: u8 = vec![1, 2, 3].into_iter().sum();
     println!("{}", s);
 }