Use ? operator for examples.

examples/hello.rs

@@ -1,9 +1,11 @@
-use rhai::Engine;
+use rhai::{Engine, EvalAltResult};
 
-fn main() {
+fn main() -> Result<(), EvalAltResult> {
     let mut engine = Engine::new();
 
-    if let Ok(result) = engine.eval::<i64>("40 + 2") {
-        println!("Answer: {}", result); // prints 42
-    }
+    let result = engine.eval::<i64>("40 + 2")?;
+
+    println!("Answer: {}", result); // prints 42
+
+    Ok(())
 }

examples/reuse_scope.rs

@@ -1,14 +1,14 @@
-use rhai::{Engine, Scope};
+use rhai::{Engine, EvalAltResult, Scope};
 
-fn main() {
+fn main() -> Result<(), EvalAltResult> {
     let mut engine = Engine::new();
     let mut scope = Scope::new();
 
-    assert!(engine
-        .eval_with_scope::<()>(&mut scope, "let x = 4 + 5")
-        .is_ok());
+    engine.eval_with_scope::<()>(&mut scope, "let x = 4 + 5")?;
 
-    if let Ok(result) = engine.eval_with_scope::<i64>(&mut scope, "x") {
-        println!("result: {}", result);
-    }
+    let result = engine.eval_with_scope::<i64>(&mut scope, "x")?;
+
+    println!("result: {}", result);
+
+    Ok(())
 }

examples/simple_fn.rs

@@ -1,6 +1,6 @@
-use rhai::{Engine, RegisterFn};
+use rhai::{Engine, EvalAltResult, RegisterFn};
 
-fn main() {
+fn main() -> Result<(), EvalAltResult> {
     let mut engine = Engine::new();
 
     fn add(x: i64, y: i64) -> i64 {
@@ -9,7 +9,9 @@ fn main() {
 
     engine.register_fn("add", add);
 
-    if let Ok(result) = engine.eval::<i64>("add(40, 2)") {
-        println!("Answer: {}", result); // prints 42
-    }
+    let result = engine.eval::<i64>("add(40, 2)")?;
+
+    println!("Answer: {}", result); // prints 42
+
+    Ok(())
 }