// SPDX-License-Identifier: MIT OR Apache-2.0
use std.convert as convert;

fn double_number(text: String) -> Result<Int, convert.ParseIntError> {
    let number = convert.parse_int(text)?;
    return Result.Ok(number * 2);
}

fn main() {
    println(match double_number("21") {
        Result.Ok(number) => convert.format_int(number),
        Result.Err(_) => "Please enter a decimal integer.",
    });
    println(match double_number("hello") {
        Result.Ok(number) => convert.format_int(number),
        Result.Err(_) => "Please enter a decimal integer.",
    });
}