用于显示给定数字不是实数的代码，如果它在C＃中包含两个点 [英] code for displaying that the given number is not a real number if it contains two dots in C#

问题描述

如果在C＃中包含两个点，则显示给定数字不是实数的代码。



我正在研究编译器构造的词法分析器阶段。我hava写了一个代码，如果它包含一个点，它将数字显示为实数，但如果它包含两个点，则它不会产生错误。

这是我的代码..........

code for displaying that the given number is not a real number if it contains two dots in C#.

i am working on lexical analyzer phase of complier construction. i hava written a code that display the number as a real number if it contains one dot int it, but if it contains two dot it does not generate an error.
here is my code..........

bool containReal = ss.Any(char.IsDigit) && ss.Contains('.');
                                       if (containReal)
                                       {
                                           MessageBox.Show("this is a Real Number");
                                           break;
                                       }
                                       //invalid b/c of two dots
                                       string str2 = ss.Substring(1, ss.IndexOf('.'));
                                       string str3 = ss.Substring(ss.IndexOf('.') + 1);
                                       bool chk_dot = (str2.Any(char.IsLetter) || str3.Any(char.IsLetter) || str2.IndexOfAny("!@%^&*()#$-_+<>".ToCharArray()) != -1 || str3.IndexOfAny("!@%^&*()#$-_+<>".ToCharArray()) != -1);
 if ( chk_dot)
                                        {
                                            MessageBox.Show("Error: Line num  " + linecount + "  Invalid b/c of two dots in a real number");
                                            errorcount++;
                                            break;

                                        }

任何人都可以请帮助我................

can anyone please help me................

推荐答案

-_ +<> .ToCharArray （））！= -1 || str3.IndexOfAny（ ！@％^& *（）＃

-_+<>".ToCharArray()) != -1 || str3.IndexOfAny("!@%^&*()#

-_ +<> .ToCharArray（））！= -1）;
if （chk_dot）
{
MessageBox.Show（ 错误：行数 + linecount + 实数中两个点的b / c无效）;
errorcount ++;
break ;

}

-_+<>".ToCharArray()) != -1); if ( chk_dot) { MessageBox.Show("Error: Line num " + linecount + " Invalid b/c of two dots in a real number"); errorcount++; break; }

任何人都可以帮助我............... 。

can anyone please help me................

使用不同的人工方法验证实数有很多问题。你不需要任何一个。比如，该号码被声明为 double 。验证是：

There are many questions on validation of real numbers using different artificial methods. You don't need any of them. Say, the number is declared as double. The the validation is:

string numericLiteral = // from input of the analyzer, part of user's code
bool isValid = double.TryParse(numericLiteral, out value);

那就是。没有人关心文字中的错误;编译器从不在错误描述中显示它。您只能显示文字的值，并告诉用户 isValid == false ：无效的数字格式。

-SA

That's is. Nobody cares what's exactly wrong in the literal; compilers never show it in the error description. You can only show the value of the literal and tell the user if isValid == false: "invalid numeric format".

—SA

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