simple + operator support

interpret.js

@@ -1,27 +1,39 @@
 let program = [
-
-  { print: 'hello' },
-  { print: 'world' }
-
+  { 
+    print: { '+': [3,5] } 
+  },
 ]
 
 let builtins = {
   print: (text) => { console.log(text) }
 }
 
+let binaryOperators = {
+  '+': (a,b) => { return a+b },
+}
+
 interpret = (program) => {
   for (let stmt of program) {
     exec(stmt)
   }
 };
 
 exec = (stmt) => {
+
+  if(typeof stmt === 'number' || typeof stmt === 'string'){
+    return stmt;
+  }
+
   let key = Object.keys(stmt)[0]
   if (typeof builtins[key] === 'function') {
-    builtins[key](stmt[key])
+    builtins[key](exec(stmt[key]))
+  } else if (typeof binaryOperators[key] === 'function') {
+    let firstArgument = stmt[key][0];
+    let secondArgument = stmt[key][1];
+    return binaryOperators[key](firstArgument, secondArgument)
   }else{
     console.error('unknown instruction: '+key)
   }
 }
 
-interpret(program)
+interpret(program)