add calculate

Author: lencx

examples/calculate/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "calculate"
+version = "0.1.0"
+authors = ["lencx <[email protected]>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

examples/calculate/src/main.rs

@@ -0,0 +1,17 @@
+macro_rules! calculate {
+    (eval $e: expr) => {{
+        {
+            let val: usize = $e; // force types to be integer
+            println!("{} = {}", stringify!($e), val);
+        }
+    }}
+}
+
+fn main() {
+    calculate! {
+        eval 1 + 2
+    }
+    calculate! {
+        eval (2 * 5) + (4 / 6)
+    }
+}