Function file_extension_previous_value 

pub fn file_extension_previous_value<V: Into<String>>(
    value: V,
) -> Result<String>

Returns the previous file extension value.

Example

use zff::*;
 
let file_extension = "z05";
assert_eq!(file_extension_previous_value(file_extension).unwrap(), "z04");

Error

fails if the file-extension is in an unsuitable format or if the previous value is < 0.