variables defined using def in a let statement now escape local scope

test added as well.

src/stl/control.rs

@@ -111,6 +111,7 @@ Since the call to some-func is the final form, its value is returned.";
 
 pub fn let_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, String> {
     let mut localsyms = syms.clone();
+    let mut locals = vec![];
     let locals_form: &Seg;
     let eval_forms: &Seg;
     if let Ctr::Seg(ref locals_form_list) = *ast.car {
@@ -156,6 +157,7 @@ pub fn let_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, String> {
                             &Seg::from_mono(Box::new(*var_val_res.unwrap().clone())),
                             None),
                     );
+                    locals.push(name.clone());
                 }
             } else if let Ctr::None = *var_form.car {
                 // nothing to declare
@@ -201,6 +203,17 @@ pub fn let_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, String> {
         return Err("evaluation failure".to_string());
     }
 
+    // we need to get any var declared from within the let eval forms
+    // those need to exist in the outside context
+    for i in localsyms.iter() {
+        if !locals.contains(i.0) && !syms.contains_key(i.0) {
+            syms.insert(
+                i.0.clone(),
+                i.1.clone(),
+            );
+        }
+    }
+
     Ok((*result).clone())
 }