num-bigint 0.1.38

Big integer implementation for Rust

A Big integer (signed version: BigInt, unsigned version: BigUint).

A BigUint is represented as a vector of BigDigits. A BigInt is a combination of BigUint and Sign.

Common numerical operations are overloaded, so we can treat them the same way we treat other numbers.


extern crate num_bigint;
extern crate num_traits;

# fn main() {
use num_bigint::BigUint;
use num_traits::{Zero, One};
use std::mem::replace;

// Calculate large fibonacci numbers.
fn fib(n: usize) -> BigUint {
    let mut f0: BigUint = Zero::zero();
    let mut f1: BigUint = One::one();
    for _ in 0..n {
        let f2 = f0 + &f1;
        // This is a low cost way of swapping f0 with f1 and f1 with f2.
        f0 = replace(&mut f1, f2);

// This is a very large number.
println!("fib(1000) = {}", fib(1000));
# }

It's easy to generate large random numbers:

extern crate rand;
extern crate num_bigint as bigint;

# #[cfg(feature = "rand")]
# fn main() {
use bigint::{ToBigInt, RandBigInt};

let mut rng = rand::thread_rng();
let a = rng.gen_bigint(1000);

let low = -10000.to_bigint().unwrap();
let high = 10000.to_bigint().unwrap();
let b = rng.gen_bigint_range(&low, &high);

// Probably an even larger number.
println!("{}", a * b);
# }

# #[cfg(not(feature = "rand"))]
# fn main() {
# }