如何验证数字 [英] How to validate numbers

问题描述

基本上，我想知道如何声明程序在有人输入字符时不会搞砸

我以为可能是

while(height！=``float'')loop等

但是这种方法不起作用，而且确实会搞砸.请帮忙！

Right basically I want to know how to declare the program to not screw up when someone enters a character

I thought it might be something like

while( height != ''float'')loop etc

but that dose not work and it does screw up. Please help!

推荐答案

您可以定义定义数字的规则，只需为此创建代码
您将需要类似以下规则的代码:
1.可以以可选的减号(``-'')
开头 2. 1个或多个数字(``0''.``9'')
3.可选的单个点(''.'')，再次为否2.

第二种选择是考虑使用正则表达式(此示例仅接受数字0..9).

You could define the rules that define a number and simply create code for that
You would need code to rules like:
1. can start with an optional minus (''-'')
2. 1 or more digits (''0''..''9'')
3. optional a single dot (''.'') and again no 2.

A second option is to consider using a regex expression (this example only accepts digits 0..9).

string Temp = "Hax00r L33t";
string Output = Regex.Replace(Temp, "[^0-9]", "");

祝你好运！

Good luck!

键盘输入验证始终是一个挑战.此函数处理一些常见情况:

Hi,

Keyboard input validation is always a challenge. This function handles some usual cases:

#include <sstream>
template <class Num>
bool Validate(const std::string& input, Num& num)
{
    Num tmp;
    std::istringstream iss(input);
    iss >> std::skipws >> tmp >> std::skipws;
    return iss.eof() && !iss.fail() ? num = tmp, true : false;
}

请检查:

Check with:

#include <iostream>
int main()
{
    std::string input;
    for (;;)
    {
        std::getline(std::cin, input); // get all input
        int i = 0;
        bool bint = Validate(input, i);
        float f = 0;
        bool bfloat = Validate(input, f);
    }
    return 0;
}

"123"，"123""-123"被验证为int和float.
"12 3"，"12 3"-123"作为int和float无效.
"123."，".123""-12.3""-.123e4"被无效为int并被验证为float.

欢呼声，
AR

"123", " 123 " "-123" are validated as int and float.
"12 3", " 12 3 " "- 123" are invalidated as int and float.
"123.", " .123 " "-12.3" " -.123e4 " are invalidated as int and validated as float.

cheers,
AR

这篇关于如何验证数字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！