isdigit函数

isdigit是计算机C(C++)语言中的一个函数，主要用于检查其参数是否为十进制数字字符。

函数定义:int isdigit(int c)
函数说明:检查参数是否为十进制数字字符(判断括号内是否为0~9的数字。)
函数所需头文件：#include<cctype>
返回值:若参数c为阿拉伯数字0~9，则返回非0值，否则返回0。

代码示例

	    //isdigit:判断字符是否为阿拉伯数字0~9
		#include<iostream>
		#include<cctype>
		 
		using namespace std;
		 
		int main()
		{
		    string str = "123456789asdfghjkl~!@#$%";
		    for(int i = 0; str[i] != 0; ++i)
		    {
		        if(isdigit(str[i]))
		            cout << str[i] << " is  digit" << endl;
		        else
		            cout << str[i] << " is not digit!" << endl;
		    }
		    
		    return 0;
		}

打印输出

标准输出：0 is  digit
1 is  digit
2 is  digit
3 is  digit
4 is  digit
5 is  digit
6 is  digit
7 is  digit
8 is  digit
9 is  digit
a is not digit!
s is not digit!
d is not digit!
f is not digit!
g is not digit!
h is not digit!
j is not digit!
k is not digit!
l is not digit!
~ is not digit!
! is not digit!
@ is not digit!
# is not digit!
$ is not digit!
% is not digit!

引经据典

https://baike.baidu.com/item/isdigit/9455880?fr=aladdin