Crate num_bigint
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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
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:
use num_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 enabled by default, and is mandatory before Rust
1.36 and the stabilized alloc crate. If you depend on num-bigint with
default-features = false, you must manually enable the std feature yourself
if your compiler is not new enough.
Random Generation
num-bigint supports the generation of random big integers when the rand
feature is enabled. To enable it include rand as
rand = "0.7"
num-bigint = { version = "0.3", features = ["rand"] }Note that you must use the version of rand that num-bigint is compatible
with: 0.7.
Compatibility
The num-bigint crate is tested for rustc 1.31 and greater.
Structs
u32 digits representation of a BigUint or BigInt,
ordered least significant digit first.u64 digits representation of a BigUint or BigInt,
ordered least significant digit first.Enums
BigInt’s composing element.