1 files changed, 83 insertions, 0 deletions
diff --git a/js/step2_eval.js b/js/step2_eval.js
new file mode 100644
index 0000000..f2cb8b1
--- /dev/null
+++ b/js/step2_eval.js
@@ -0,0 +1,83 @@
+var types = require('./types');
+var reader = require('./reader');
+if (typeof module !== 'undefined') {
+    var readline = require('./node_readline');
+}
+
+// read
+function READ(str) {
+    return reader.read_str(str);
+}
+
+// eval
+function eval_ast(ast, env) {
+    if (types.symbol_Q(ast)) {
+        return env[ast];
+    } else if (types.list_Q(ast)) {
+        return ast.map(function(a) { return EVAL(a, env); });
+    } else if (types.vector_Q(ast)) {
+        var v = ast.map(function(a) { return EVAL(a, env); });
+        v.__isvector__ = true;
+        return v;
+    } else if (types.hash_map_Q(ast)) {
+        var new_hm = {};
+        for (k in ast) {
+            new_hm[EVAL(k, env)] = EVAL(ast[k], env);
+        }
+        return new_hm;
+    } else {
+        return ast;
+    }
+}
+
+function _EVAL(ast, env) {
+    if (!types.list_Q(ast)) {
+        return eval_ast(ast, env);
+    }
+
+    // apply list
+    var el = eval_ast(ast, env), f = el[0];
+    return f.apply(f, el.slice(1));
+}
+
+function EVAL(ast, env) {
+    var result = _EVAL(ast, env);
+    return (typeof result !== "undefined") ? result : null;
+}
+
+// print
+function PRINT(exp) {
+    return types._pr_str(exp, true);
+}
+
+// repl
+repl_env = {};
+var rep = function(str) { return PRINT(EVAL(READ(str), repl_env)); };
+
+repl_env['+'] = function(a,b){return a+b;};
+repl_env['-'] = function(a,b){return a-b;};
+repl_env['*'] = function(a,b){return a*b;};
+repl_env['/'] = function(a,b){return a/b;};
+
+if (typeof require === 'undefined') {
+    // Asynchronous browser mode
+    readline.rlwrap(function(line) { return rep(line); },
+                    function(exc) {
+                        if (exc instanceof reader.BlankException) { return; }
+                        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 instanceof reader.BlankException) { continue; }
+            if (exc.stack) { console.log(exc.stack); } else { console.log(exc); }
+        }
+    }
+} else {
+    exports.rep = rep;
+}