Character classification in C++ is possible using functions specified in function library . Numerous function to classify characters are discussed in this article.
1. isalpha() : This function returns true if character is an alphabet else returns false. All the characters from a-z and A-Z return true according to this function.
2. isalnum() : This function returns true if character is an alphabet or a number else returns false. All the characters from a-z , A-Z and all numbers return true according to this function.
3. isdigit() : This function returns true if character is a number else returns false. All all numbers return true according to this function.
// C++ program to demonstrate insalpha(), isnum() // and isdigit() #include <cctype> #include <iostream> using namespace std; int main() { // initializing character array char ch[5] = "g1"; // checking for isalpha() function for (int i=0; i<2; i++) { if (isalpha(ch[i])) cout << ch[i] << " is alphabet" << endl; else cout << ch[i] << " is not alphabet" << endl; } cout << endl; // checking for isalnum() function for (int i=0; i<2; i++) { if (isalnum(ch[i])) cout << ch[i] << " is alphanumeric" << endl; else cout << ch[i] << " is not alphanumeric" << endl; } cout << endl; // checking for isdigit() function for (int i=0; i<2; i++) { if (isdigit(ch[i])) cout << ch[i] << " is digit" << endl; else cout << ch[i] << " is not digit" << endl; } } |
Output :
g is alphabet 1 is not alphabet g is alphanumeric 1 is alphanumeric g is not digit 1 is digit
4. isblank() : This function returns true if character is a space or tab else returns false.
5. isspace() : This function returns true if character is a space or tab or whitespace control code ( Eg. , ) else returns false.
6. iscntrl() : This function returns true if character is tab or any control code else returns false.
// C++ program to demonstrate iscntrl(), isblank() and // isspace() #include <cctype> #include <iostream> using namespace std; int main() { // initializing character array char ch[4] = "
"; // checking for iscntrl() function for (int i=0; i<3; i++) { if (iscntrl(ch[i])) cout << " Character is control code " << endl; else cout << " Character is not control code" << endl; } cout << endl; // checking for isblank() function for (int i=0; i<3; i++) { if (isblank(ch[i])) cout << " Character is blank" << endl; else cout << " Character is not blank" << endl; } cout << endl; // checking for isspace() function for (int i=0; i<3; i++) { if (isspace(ch[i])) cout << " Character is space" << endl; else cout << " Character is not space" << endl; } } |
Output :
Character is not control code Character is control code Character is control code Character is blank Character is not blank Character is blank Character is space Character is space Character is space
7. isprint() : This function returns true if character is printable on console i.e. all characters except control code else returns false.
8. isxdigit() : This function returns true if character is hexadecimal i.e 0-9 and a-f else returns false.
9. ispunct() : This function returns true if character is punctuation mark else returns false.
// C++ program to demonstrate isprint(), isxdigit() and // ispunct() #include <cctype> #include <iostream> using namespace std; int main() { // initializing character array char ch[6] = " @gf1"; // checking for isprint() function for (int i=0; i<5; i++) { if (isprint(ch[i])) cout << ch[i] << " is printable character " << endl; else cout << ch[i] << " is not printable Character" << endl; } cout << endl; // checking for isxdigit() function for (int i=0; i<5; i++) { if (isxdigit(ch[i])) cout << ch[i] << " is hexadecimal Character" << endl; else cout << ch[i] << " is not hexadecimal Character" << endl; } cout << endl; // checking for ispunct() function for (int i=0; i<5; i++) { if (ispunct(ch[i])) cout << ch[i] << " is punctuation mark" << endl; else cout << ch[i] << " is not punctuation mark" << endl; } } |
Output :
is not printable Character @ is printable character g is printable character f is printable character 1 is printable character is not hexadecimal Character @ is not hexadecimal Character g is not hexadecimal Character f is hexadecimal Character 1 is hexadecimal Character is not punctuation mark @ is punctuation mark g is not punctuation mark f is not punctuation mark 1 is not punctuation mark
Reference : http://www.cplusplus.com/reference/cctype/
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