1 files changed, 40 insertions, 0 deletions
diff --git a/js/env.js b/js/env.js
new file mode 100644
index 0000000..3c9eac8
--- /dev/null
+++ b/js/env.js
@@ -0,0 +1,40 @@
+// Node vs browser behavior
+var env = {};
+if (typeof module === 'undefined') {
+    var exports = env;
+}
+
+// Env implementation
+function Env(outer, binds, exprs) {
+    this.data = {};
+    this.outer = outer || null;
+
+    if (binds && exprs) {
+        // Returns a new Env with symbols in binds bound to
+        // corresponding values in exprs
+        // TODO: check types of binds and exprs and compare lengths
+        for (var i=0; i<binds.length;i++) {
+            if (binds[i].value === "&") {
+                // variable length arguments
+                this.data[binds[i+1].value] = Array.prototype.slice.call(exprs, i);
+                break;
+            } else {
+                this.data[binds[i].value] = exprs[i];
+            }
+        }
+    }
+    return this;
+}
+Env.prototype.find = function (key) {
+    if (key in this.data) { return this; }
+    else if (this.outer) {  return this.outer.find(key); }
+    else { return null; }
+};
+Env.prototype.set = function(key, value) { this.data[key] = value; return value; },
+Env.prototype.get = function(key) {
+    var env = this.find(key);
+    if (!env) { throw new Error("'" + key + "' not found"); }
+    return env.data[key];
+};
+
+exports.Env = env.Env = Env;