readFn vars [(StrVar "float")] =
    do line <- getLine
       return $ Map.insert "return" (DblVar $ read line) vars
readFn vars [(StrVar "float")] =
    do line <- getLine
       return $ Map.insert "return" (DblVar $ read line) vars
readFn vars [(StrVar "float")] =
    do line <- getLine
       return $ Map.insert "return" (DblVar $ read line) vars