在do ... while中将相关表达式匹配设置为false [英] Setting a relevant expression match to false in a do...while

问题描述

我正在尝试编写一些非常基本的代码，但是我也在正则表达式方面挑战自己.我一直可以弄清整个代码，但是我真正遇到的一个问题是，我试图在表达式为假的情况下运行do ... while循环.在这一点上，我绝对没有错误，但是do ... while循环一直在运行.

我在下面附上相关代码，希望对您有所帮助.

提前谢谢

  if(tollResponse ==是"){Console.WriteLine(您每次旅行要付多少钱?");字符串tollTax = Console.ReadLine();匹配费用= Regex.Match(tollTax，@"[\ d.] +");如果(收费成功){Math.Round(Convert.ToDecimal(tollTax)，2);Console.WriteLine(好主啊，这是你的钱");}别的{做{Console.WriteLine(请输入正确的数字");tollTax = Console.ReadLine();}while(toll.Success == false);}} 

解决方案

简单的编码错误...在代码中添加了注释以解释问题

  if(tollResponse ==是"){Console.WriteLine(您每次旅行要付多少钱?");字符串tollTax = Console.ReadLine();//toll.Success在这里设置.匹配费用= Regex.Match(tollTax，@"[\ d.] +");如果(收费成功){//不确定为什么要这样做，因为在给定的代码中没有使用它Math.Round(Convert.ToDecimal(tollTax)，2);Console.WriteLine(好主啊，这是你的钱");}别的{//这是一个无限循环，因为toll.Success不再设置.做{Console.WriteLine(请输入正确的数字");tollTax = Console.ReadLine();} while(toll.Success == false);}} 

---

我想你想要的

  if(tollResponse ==是"){Console.WriteLine(您每次旅行要付多少钱?");//使用else语句遍历Console.ReadLine()并在第一次正确时退出做{字符串tollTax = Console.ReadLine();//toll.Success在这里设置.匹配费用= Regex.Match(tollTax，@"^ [+-]?[0-9] {1,3}(?:，?[0-9] {3})*(?:\.[0-9] {2})?$)；如果(收费成功){Console.WriteLine(好主啊，这是你的钱");//将退出}别的{Console.WriteLine(请输入正确的数字");}} while(toll.Success == false);} 

注意::还删除了1行重复代码，更新为使用我推荐的正则表达式，并删除了 Math.Round

---

正则表达式工具

  [\ d.] + 

说明:

 数字(必需十进制)^ [+-]?[0-9] {1,3}(?:，?[0-9] {3})* \.[0-9] {2} $选项:不区分大小写在字符串«^»的开头声明位置匹配«[+-]?»下面列表中的单个字符在零到一遍之间，尽可能多地遍历，并根据需要回馈(贪婪)«?»字符"+"«+»人物 "-" "-"匹配"0"和"9"之间的单个字符«[0-9] {1,3}»在1至3次之间，尽可能多地进行，根据需要进行回馈(贪婪)«{1,3}»匹配«(?:，?[0-9] {3})*»下的正则表达式在0到无限制的时间之间，尽可能地多次，并根据需要进行回馈(贪婪)«*»匹配字符，"，字面上是«，?»在零到一遍之间，尽可能多地遍历，并根据需要回馈(贪婪)«?»匹配"0"和"9"之间的单个字符«[0-9] {3}»恰好是"{3}"的3倍匹配字符."字面上地 "\."匹配"0"和"9"之间的单个字符«[0-9] {2}»恰好是"{2}"的2倍在字符串结尾处声明位置(或在字符串结尾处的换行符之前，如果有的话)«$» 

将匹配:

  1,432.01456.56654,246.43432321,5431423972921379312.32 

将不匹配

  324,123.432,,, 312，.32123，.23 

取自我的答案

解决方案

Simple coding bug...comments added to your code to explain issue

if (tollResponse == "yes")
{
    Console.WriteLine("How much do you pay per trip?");
    string tollTax = Console.ReadLine();
    //toll.Success gets set here.
    Match toll = Regex.Match(tollTax, @"[\d .]+");

    if (toll.Success)
    {
        //Not sure why you are doing this since you aren't using it in the given code
        Math.Round(Convert.ToDecimal(tollTax), 2);
        Console.WriteLine("Good lord that's high... well it's your money");
    }
    else
    {
        //This is an infinite loop because toll.Success is never set again.
        do
        {
            Console.WriteLine("Please enter a proper number");
            tollTax = Console.ReadLine();
        } while (toll.Success == false);
    }
}

---

What i think you want

if (tollResponse == "yes")
{
    Console.WriteLine("How much do you pay per trip?");

    //Loop over the Console.ReadLine() using the else statement and exit if it is right the first time
    do
    {
        string tollTax = Console.ReadLine();
        //toll.Success gets set here.
        Match toll = Regex.Match(tollTax, @"^[+-]?[0-9]{1,3}(?:,?[0-9]{3})*(?:\.[0-9]{2})?$");

        if (toll.Success)
        {
            Console.WriteLine("Good lord that's high... well it's your money");
            //will exit
        }
        else
        {
            Console.WriteLine("Please enter a proper number");
        } 
    } while (toll.Success == false);
}

Note: Removed 1 line of duplicate code as well, updated to use my recommended regex and removed Math.Round

---

Regex Tool

[\d .]+

Debuggex Demo

A more Valid Regex for currency

decimal optional (two decimal places)

^[+-]?[0-9]{1,3}(?:,?[0-9]{3})*(?:\.[0-9]{2})?$

Debuggex Demo

Explained:

number (decimal required)

^[+-]?[0-9]{1,3}(?:,?[0-9]{3})*\.[0-9]{2}$

Options: case insensitive

Assert position at the beginning of the string «^»
Match a single character present in the list below «[+-]?»
   Between zero and one times, as many times as possible, giving back as needed (greedy) «?»
   The character "+" «+»
   The character "-" «-»
Match a single character in the range between "0" and "9" «[0-9]{1,3}»
   Between one and 3 times, as many times as possible, giving back as needed (greedy) «{1,3}»
Match the regular expression below «(?:,?[0-9]{3})*»
   Between zero and unlimited times, as many times as possible, giving back as needed (greedy) «*»
   Match the character "," literally «,?»
      Between zero and one times, as many times as possible, giving back as needed (greedy) «?»
   Match a single character in the range between "0" and "9" «[0-9]{3}»
      Exactly 3 times «{3}»
Match the character "." literally «\.»
Match a single character in the range between "0" and "9" «[0-9]{2}»
   Exactly 2 times «{2}»
Assert position at the end of the string (or before the line break at the end of the string, if any) «$»

Will Match:

1,432.01
456.56
654,246.43
432
321,543
14239729
21379312.32

Will not Match

324,123.432
,,,312,.32
123,.23

taken from my answer here php - regex - how to extract a number with decimal (dot and comma) from a string (e.g. 1,120.01)?

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