(C++) CanLexicalCast

January 11, 2018 · View on GitHub

(C++) CanLexicalCast

CanLexicalCast is a Checking code snippet that let you check if you can convert a std::string to another data type using boost::lexical_cast.

`#include <cassert> #include <string> #include <boost/lexical_cast.hpp> //From http://www.richelbilderbeek.nl/CppCanLexicalCast.htm template <class TargetType> bool CanLexicalCast(const std::string& from) { try { boost::lexical_cast<TargetType>(from); } catch (boost::bad_lexical_cast) { return false; } catch (...) { assert(!"Something unexpected happened"); throw; } return true; }`

Comparison between CanCast and CanLexicalCast

The table below shows if a std::string can be converted according to CanCast (CC) and CanLexicalCast (CLC). Note that the first std::string was a space (' '). Below the table I show the code I've used to generate this output. CanCast serves the same purpose as CanLexicalCast, but does not throw an exception and does not use Boost. Note that there are differences between CanCast and CanLexicalCast, as CanLexicalCast is more strict.

#include <vector> int main() { std::vector<std::string> v; v.push_back(""); v.push_back("a"); v.push_back("1"); v.push_back("1,1"); v.push_back("1.1"); v.push_back("1.1.1"); v.push_back("-1"); v.push_back("-1.1"); v.push_back("-1.1.1"); std::cout << "Type" << '\t' << "int" << '\t' << "int" << '\t' << "double" << '\t' << "double" << std::endl; std::cout << "string" << '\t' << "CC" << '\t' << "CLC" << '\t' << "CC" << '\t' << "CLC" << std::endl; std::cout << std::boolalpha; const std::size_t size = v.size(); for (std::size_t i=0; i!=size; ++i) { std::cout << v[i] << '\t' << CanCast<int>(v[i]) << '\t' << CanLexicalCast<int>(v[i]) << '\t' << CanCast<double>(v[i]) << '\t' << CanLexicalCast<double>(v[i]) << '\n'; } }