Crate num_bigint
source · [−]Expand description
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.
Example
extern crate num_bigint;
extern crate num_traits;
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);
}
f0
}
// 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;
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);
See the “Features” section for instructions for enabling random number generation.
Features
The std crate feature is mandatory and enabled by default. If you depend on
num-bigint with default-features = false, you must manually enable the
std feature yourself. In the future, we hope to support #![no_std] with
the alloc crate when std is not enabled.
Implementations for i128 and u128 are only available with Rust 1.26 and
later. The build script automatically detects this, but you can make it
mandatory by enabling the i128 crate feature.
Random Generation
num-bigint supports the generation of random big integers when the rand
feature is enabled. To enable it include rand as
rand = "0.5"
num-bigint = { version = "0.2", features = ["rand"] }Note that you must use the version of rand that num-bigint is compatible
with: 0.5.
Compatibility
The num-bigint crate is tested for rustc 1.15 and greater.
Structs
Enums
A Sign is a BigInt’s composing element.