41 wiersze
1.1 KiB
Rust
41 wiersze
1.1 KiB
Rust
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//-- #########################
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//-- Task: Implementing mapt for Result
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//-- Author: Vigneshwer.D
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//-- Version: 1.0.0
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//-- Date: 26 March 17
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//-- #########################
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use std::num::ParseIntError;
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// With the return type rewritten, we use pattern matching without `unwrap()`.
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fn double_number(number_str: &str) -> Result<i32, ParseIntError> {
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match number_str.parse::<i32>() {
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Ok(n) => Ok(2 * n),
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Err(e) => Err(e),
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}
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}
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// As with `Option`, we can use combinators such as `map()`.
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// This function is otherwise identical to the one above and reads:
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// Modify n if the value is valid, otherwise pass on the error.
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fn double_number_map(number_str: &str) -> Result<i32, ParseIntError> {
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number_str.parse::<i32>().map(|n| 2 * n)
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}
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fn print(result: Result<i32, ParseIntError>) {
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match result {
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Ok(n) => println!("n is {}", n),
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Err(e) => println!("Error: {}", e),
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}
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}
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fn main() {
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// This still presents a reasonable answer.
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let twenty = double_number("10");
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print(twenty);
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// The following now provides a much more helpful error message.
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let tt = double_number_map("t");
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print(tt);
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}
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