f# stackoverflow 项目 euler #4 [英] f# stackoverflow project euler #4

问题描述

我正在处理 Project Euler 的问题四，并且遇到了 stackoverflow 异常.我不是在寻求解决问题的帮助，我只是想解释为什么我遇到了stackoverflow异常.这通常是因为无限递归，但我不相信这次是这种情况(如果我只是瞎了，现在没看到，请告诉我).

I'm working on problem four of Project Euler and am running into a stackoverflow exception. I'm not asking for help on solving the problem, I'd just like it explained why I am getting a stackoverflow exception. It's usually because of infinite recursion but I don't believe that is the case this time (if I'm just blind and not seeing it right now please let me know).

代码如下:

let Euler4 =

let reverse sum =
    let rec loop (n,x) =
        if n = 0
        then
            x
        else
            loop (n/10,(x*10) + (n%10))

    loop (sum, 0);

let isPalindrome arg = (arg = (reverse arg));

let findPalindromes (startx,starty) =
    let rec loop (x,y) acc =
        let result = if isPalindrome (x * y) then ((x,y) :: acc) else acc;
        let next = match (x,y) with
            | (x,y) when y = 100 -> (x-1,starty)
            | _ -> (x,y-1)
        if x = 100 then
            result
        else
            loop (next) result

    loop (startx,starty) [];


let value = (999,999);
printfn "%A" (findPalindromes value);

;

推荐答案

您是在调试"模式还是发布"模式下编译?VS 中的调试模式默认关闭尾调用(编译器标志--tailcalls-")，以保留用于调试的堆栈，但这需要权衡 StackOverflow.您可以切换到发布"模式，或者

Are you compiling in 'Debug' mode or 'Release' mode? Debug mode in VS has tail calls turned off by default (compiler flag "--tailcalls-"), in order to preserve stacks for debugging, but this has the trade-off that you may StackOverflow. You can either switch to 'Release' mode, or

• 右键单击解决方案资源管理器中的项目属性，选择属性"
• 转到构建"标签
• 确保选择了调试"配置
• 点击生成尾调用"框

使用调试"设置打开尾调用.

to turn on tail calls with 'Debug' settings.

(你的程序在启用尾调用的情况下运行良好.)

(Your program runs fine for me with tail calls enabled.)

这篇关于f# stackoverflow 项目 euler #4的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！