refactored ast tables, added eval method

ast/var_table.go

@@ -19,21 +19,27 @@ package ast
 
 type VarTable map[string]*Token
 
-var (
-    GlobalVarTable *VarTable
-)
+func (VarTable vt) GetVar(arg string) *Token {
+    val, ok := vt[arg]
+    if !ok {
+        return nil
+    }
+
+    return val
+}
 
 // Library represents variables defined in inner scope
 // It is assumed library is ordered from innermost scope to outermost scope
 func GetVar(arg string, library []VarTable) *Token {
-    for scope, dict := range library {
-        val, ok := dict[arg]
-        if ok {
-            scope = scope // TEMP LINE
-            // TODO: maybe log which scope it was found in?
-            return val
+    var res *Token
+    res = nil
+    for i := 0; i < len(library); i += 1 {
+        res = library[i].GetVar(arg)
+        if res != nil {
+            // TODO: Log scope res was found in?
+            break
         }
     }
 
-    return nil
+    return res
 }