(C++) std::isdigit

 

std::isdigit is an STL function to test of a character is a decimal digit.

 

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#include <cassert> #include <string> int main() {   const std::string s = "1a";   //'a' is no decimal digit   assert( std::isdigit(s[0]));   assert(!std::isdigit(s[1]));   //'a' is a hexadecimal digit   assert( std::isxdigit(s[0]));   assert( std::isxdigit(s[1])); }