1 files changed, 42 insertions, 0 deletions
diff --git a/js/step0_repl.js b/js/step0_repl.js
new file mode 100644
index 0000000..5fa10f2
--- /dev/null
+++ b/js/step0_repl.js
@@ -0,0 +1,42 @@
+if (typeof module !== 'undefined') {
+    var readline = require('./node_readline');
+}
+
+// read
+function READ(str) {
+    return str;
+}
+
+// eval
+function EVAL(ast, env) {
+    return eval(ast);
+}
+
+// print
+function PRINT(exp) {
+    return exp;
+}
+
+// repl
+var rep = function(str) { return PRINT(EVAL(READ(str), {})); };
+
+if (typeof require === 'undefined') {
+    // Asynchronous browser mode
+    readline.rlwrap(function(line) { return rep(line); },
+                    function(exc) {
+                        if (exc.stack) { console.log(exc.stack); } else { console.log(exc); }
+                    });
+} else if (require.main === module) {
+    // Synchronous node.js commandline mode
+    while (true) {
+        var line = readline.readline("user> ");
+        if (line === null) { break; }
+        try {
+            if (line) { console.log(rep(line)); }
+        } catch (exc) {
+            if (exc.stack) { console.log(exc.stack); } else { console.log(exc); }
+        }
+    }
+} else {
+    exports.rep = rep;
+}