Testing Whether a String Contains a Valid Number - C++ boost

C++ examples for boost:Number

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Introduction

Boost lexical_cast function template can check if the string contains a valid number.

A valid number can include a preceding minus sign, or a preceding plus sign, but not whitespace. 

#include <iostream>
#include <boost/lexical_cast.hpp>

using namespace std;
using boost::lexical_cast;
using boost::bad_lexical_cast;

template<typename T>
bool isValid(const string& num) {

   bool res = true;
   try {
      T tmp = lexical_cast<T>(num);
   }
   catch (bad_lexical_cast &e) {
      res = false;
   }

   return(res);
}

void test(const string& s) {

   if (isValid<int>(s))
      cout << s << " is a valid integer." << endl;
   else
      cout << s << " is NOT a valid integer." << endl;

   if (isValid<double>(s))
      cout << s << " is a valid double." << endl;
   else
      cout << s << " is NOT a valid double." << endl;

   if (isValid<float>(s))
      cout << s << " is a valid float." << endl;
   else
      cout << s << " is NOT a valid float." << endl;
}

int main() {

   test("12345");
   test("1.23456");
   test("-1.23456");
   test(" - 1.23456");
   test("+1.23456");
   test("  1.23456  ");
   test("asdf");
}

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