added shell tab complete

ast/var_table.go

@@ -73,6 +73,18 @@ func SetVar(variable string, value *Token, vt VarTable) {
     }
 }
 
+/* lists all vars in tables
+ */
+func ListVars(vt VarTable) []string {
+    keys := make([]string, len(*vt))
+    i := 0
+    for k := range *vt {
+        keys[i] = k
+    }
+
+    return keys
+}
+
 // Library represents variables defined in inner scope
 // It is assumed library is ordered from innermost scope to outermost scope
 func GetVarFromTables(arg string, library []VarTable) *Token {