Add fallible functions support and replace most arithmetic operations with checked versions.

tests/math.rs

@@ -0,0 +1,40 @@
+use rhai::{Engine, EvalAltResult};
+
+#[test]
+fn test_math() -> Result<(), EvalAltResult> {
+    let mut engine = Engine::new();
+
+    assert_eq!(engine.eval::<i64>("1 + 2")?, 3);
+    assert_eq!(engine.eval::<i64>("1 - 2")?, -1);
+    assert_eq!(engine.eval::<i64>("2 * 3")?, 6);
+    assert_eq!(engine.eval::<i64>("1 / 2")?, 0);
+    assert_eq!(engine.eval::<i64>("3 % 2")?, 1);
+    assert_eq!(
+        engine.eval::<i64>("(-9223372036854775807).abs()")?,
+        9223372036854775807
+    );
+
+    // Overflow/underflow/division-by-zero errors
+    match engine.eval::<i64>("9223372036854775807 + 1") {
+        Err(EvalAltResult::ErrorArithmetic(_, _)) => (),
+        r => panic!("should return overflow error: {:?}", r),
+    }
+    match engine.eval::<i64>("(-9223372036854775807) - 2") {
+        Err(EvalAltResult::ErrorArithmetic(_, _)) => (),
+        r => panic!("should return underflow error: {:?}", r),
+    }
+    match engine.eval::<i64>("9223372036854775807 * 9223372036854775807") {
+        Err(EvalAltResult::ErrorArithmetic(_, _)) => (),
+        r => panic!("should return overflow error: {:?}", r),
+    }
+    match engine.eval::<i64>("9223372036854775807 / 0") {
+        Err(EvalAltResult::ErrorArithmetic(_, _)) => (),
+        r => panic!("should return division by zero error: {:?}", r),
+    }
+    match engine.eval::<i64>("9223372036854775807 % 0") {
+        Err(EvalAltResult::ErrorArithmetic(_, _)) => (),
+        r => panic!("should return division by zero error: {:?}", r),
+    }
+
+    Ok(())
+}