Implement calculating

src/eval.rs

@@ -0,0 +1,34 @@
+use crate::tokenizer::Token;
+
+pub fn eval(tokens: Vec<Token>) -> i32 {
+  let mut stack = Vec::new();
+
+  for t in tokens {
+    match t {
+      Token::Number(val) => stack.push(val),
+      Token::Addition => {
+        let right = stack.pop().unwrap();
+        let left = stack.pop().unwrap();
+        stack.push(left + right);
+      },
+      Token::Substruction => {
+        let right = stack.pop().unwrap();
+        let left = stack.pop().unwrap();
+        stack.push(left - right);
+      },
+      Token::Multiplication => {
+        let right = stack.pop().unwrap();
+        let left = stack.pop().unwrap();
+        stack.push(left * right);
+      },
+      Token::Division => {
+        let right = stack.pop().unwrap();
+        let left = stack.pop().unwrap();
+        stack.push(left / right);
+      },
+      _ => {}
+    }
+  }
+
+  return stack.pop().unwrap();
+}

src/main.rs

@@ -7,6 +7,9 @@ use tokenizer::tokenizer;
 mod rpn;
 use rpn::to_rpn;
 
+mod eval;
+use eval::eval;
+
 
 fn main() {
   let stdin = io::stdin();
@@ -20,6 +23,9 @@ fn main() {
 
     let tokens = tokenizer(&buffer);
     let rpn = to_rpn(tokens);
+    let res = eval(rpn);
+
+    println!("= {}\n", res);
 
     buffer.clear();
   }