Update example for changes in float behavior

Author: ehuss

src/expressions/operator-expr.md

@@ -444,9 +444,9 @@ reference types and `mut` or `const` in pointer types.
   assert_eq!(42.9f32 as i32, 42);
   assert_eq!(-42.9f32 as i32, -42);
   assert_eq!(42_000_000f32 as i32, 42_000_000);
-  println!("Undefined Behavior: {}", 1_000_000_000_000_000f32 as i32);
-  println!("Undefined Behavior: {}", std::f32::NEG_INFINITY as i32);
-  println!("Undefined Behavior: {}", std::f32::NAN as i32);
+  assert_eq!(std::f32::NAN as i32, 0);
+  assert_eq!(1_000_000_000_000_000f32 as i32, 0x7fffffffi32);
+  assert_eq!(std::f32::NEG_INFINITY as i32, -0x80000000i32);
   ```
 
 * Casting from an integer to float will produce the closest possible float \*