improve repl

server/repl.js

@@ -6,13 +6,32 @@ import vm from "./vm.js";
 const rl = readline.createInterface({
   input: process.stdin,
   output: process.stdout,
-  prompt: 'OHAI> '
+  prompt: 'λ '
 });
 
 rl.prompt();
 
+var last;
+
 rl.on('line', (line) => {
-  console.log(vm.evaluateString(line));
+  try {
+    if (line.trim().length == 0) {
+      rl.prompt();
+    }
+    else {
+      last = vm.evaluateString(line);
+      if (last == undefined) {
+        rl.prompt();
+      }
+      else {
+        console.log(last);
+        vm.env.bindings["it"] = last;
+      }
+    }
+  }
+  catch (e) {
+    console.log(e.errormessage);
+  }
   rl.prompt();
 }).on('close', () => {
   console.log('Bye');

server/vm.js

@@ -90,6 +90,9 @@ function evaluate(ast, environment) {
   else if (ast.exprType === "Name") {
     return lookup(ast.ident, environment);
   }
+  else if (ast.exprType === "Bool") {
+    return ast.val;
+  }
   else if (ast.exprType === "If") {
     if (evaluate(ast.condition, environment)) {
       return evaluate(ast.thenexp, environment);
@@ -117,5 +120,6 @@ function evaluate(ast, environment) {
 }
 
 export default {
-  evaluateString : evaluateString
+  evaluateString : evaluateString,
+  env : testenv
 };