递归函数计算阶乘导致堆栈溢出 [英] Recursive function calculating factorials leads to stack overflow

问题描述

我在Rust中尝试了递归阶乘算法。我使用的是此版本的编译器：

I tried a recursive factorial algorithm in Rust. I use this version of the compiler:

rustc 1.12.0 (3191fbae9 2016-09-23)
cargo 0.13.0-nightly (109cb7c 2016-08-19)

代码：

extern crate num_bigint;
extern crate num_traits;

use num_bigint::{BigUint, ToBigUint};
use num_traits::One;

fn factorial(num: u64) -> BigUint {
    let current: BigUint = num.to_biguint().unwrap();
    if num <= 1 {
        return One::one();
    }
    return current * factorial(num - 1);
}

fn main() {
    let num: u64 = 100000;
    println!("Factorial {}! = {}", num, factorial(num))
}

我收到此错误：

$ cargo run

thread 'main' has overflowed its stack
fatal runtime error: stack overflow
error: Process didn't exit successfully

如何解决？以及为什么在使用Rust时会看到此错误？

How to fix that? And why do I see this error when using Rust?

推荐答案

Rust没有尾调用消除功能，因此递归受到限制根据您的堆栈大小。将来可能会成为Rust的功能（您可以在 Rust FAQ ），但与此同时，您将不必递归那么深或使用循环。

Rust doesn't have tail call elimination, so your recursion is limited by your stack size. It may be a feature for Rust in the future (you can read more about it at the Rust FAQ), but in the meantime you will have to either not recurse so deep or use loops.

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