C++ isalpha() / isdigit() / isalnum() / islower() / isupper()

       isalpha() / isdigit() / isalnum() / islower() / isupper()参数为字符型变量，分别用于判断字符是否为字母 / 数字(注意是字符型) / 字母或数字 / 小写字母 / 大写字母。如果是，返回非0；如果不是，返回0。

#include<bits/stdc++.h>

using namespace std;

int main(){
	char ch = 'Z';
	cout << "isalpha: " << isalpha(ch) << endl;
	cout << "isdigit: " << isdigit(ch) << endl;
	cout << "isalnum: " << isalnum(ch) << endl;
	cout << "islower: " << islower(ch) << endl;
	cout << "isupper: " << isupper(ch) << endl;
    return 0;
} 

isalpha: 1
isdigit: 0
isalnum: 1
islower: 0
isupper: 1

--------------------------------
Process exited after 0.2368 seconds with return value 0
请按任意键继续. . .

#include<bits/stdc++.h>

using namespace std;

int main(){
	char ch = '9';
	cout << "isalpha: " << isalpha(ch) << endl;
	cout << "isdigit: " << isdigit(ch) << endl;
	cout << "isalnum: " << isalnum(ch) << endl;
	cout << "islower: " << islower(ch) << endl;
	cout << "isupper: " << isupper(ch) << endl;
    return 0;
} 

isalpha: 0
isdigit: 1
isalnum: 4
islower: 0
isupper: 0

--------------------------------
Process exited after 2.475 seconds with return value 0
请按任意键继续. . .