rust create bigint from string

Rust provides the FromStr trait for converting a string into a BigUint (a big integer type). You can use the parse method from the FromStr trait to convert a string into a BigUint. Here's an example:

use num::BigUint;
use std::str::FromStr;

fn main() {
    let number_str = "1234567890";
    let big_int = BigUint::from_str(number_str).unwrap();
    println!("Big integer: {:?}", big_int);
}

In this example, the number_str variable holds the string representation of the big integer. We use the from_str method from the FromStr trait to parse the string and convert it into a BigUint value. If the parsing is successful, we can use the unwrap method to get the actual BigUint value. Finally, we print the big integer using println!.

Make sure to add the num crate to your Cargo.toml file to use the BigUint type and the FromStr trait.