rustlings/exercises/13_error_handling/errors3.rs

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// This is a program that is trying to use a completed version of the
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// `total_cost` function from the previous exercise. It's not working though!
// Why not? What should we do to fix it?
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use std::num::ParseIntError;
fn main() {
let mut tokens = 100;
let pretend_user_input = "8";
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let cost = total_cost(pretend_user_input)?;
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if cost > tokens {
println!("You can't afford that many!");
} else {
tokens -= cost;
println!("You now have {} tokens.", tokens);
}
}
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fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
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let processing_fee = 1;
let cost_per_item = 5;
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let qty = item_quantity.parse::<i32>()?;
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Ok(qty * cost_per_item + processing_fee)
}