lexical_eval

Handy C++11 function similar to lexical_cast with some added support for scientific notation, octal, and hexadecimal. The main focus of lexical_eval is correctly casting std::string objects into C++ fundamental types (like bool, int, char) according to rules normally honored by the C++ scanner.

Some examples:

• lexical_eval<int>("3") = 3
• lexical_eval<int>("0xFF") = 255
• lexical_eval<int>("0777") = 511

Usage

Copy include/lexical_eval.hpp into your include path and just include where you'd like to use it.

#include <iostream>
#include <string>
#include <lexical_eval.hpp>

int main() {
  std::string s;
  std::cout << "Enter a number: ";
  std::cin >> s;
  std::cout << "As integer: " << lexical_eval<int>(s) << std::endl;
  std::cout << "As floating point: " << lexical_eval<float>(s) << std::endl;
}

Notes

• lexical_eval assumes you probably would like the numeric data over the character data, so calls to it with std::string as the source and char as the target follow this rule, which is not usual for stream semantics. There are better ways to extract character data from strings; this is not one of them.
• Currently lexical_eval is not very safe, as no exceptions are thrown for bad inputs, so use judiciously.