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- // Copyright Antony Polukhin, 2013-2019.
- // Distributed under the Boost Software License, Version 1.0.
- // (See the accompanying file LICENSE_1_0.txt
- // or a copy at <http://www.boost.org/LICENSE_1_0.txt>.)
- //[lexical_cast_variant_to_long_double
- /*`
- In this example we'll make a `to_long_double` method that converts value of the Boost.Variant to `long double`.
- */
- #include <boost/lexical_cast.hpp>
- #include <boost/variant.hpp>
- #include <cassert>
- struct to_long_double_functor: boost::static_visitor<long double> {
- template <class T>
- long double operator()(const T& v) const {
- // Lexical cast has many optimizations including optimizations for situations that usually
- // occur in generic programming, like std::string to std::string or arithmetic type to arithmetic type conversion.
- return boost::lexical_cast<long double>(v);
- }
- };
- // Throws `boost::bad_lexical_cast` if value of the variant is not convertible to `long double`
- template <class Variant>
- long double to_long_double(const Variant& v) {
- return boost::apply_visitor(to_long_double_functor(), v);
- }
- int main() {
- boost::variant<char, int, std::string> v1('0'), v2("10.0001"), v3(1);
- const long double sum = to_long_double(v1) + to_long_double(v2) + to_long_double(v3);
- const int ret = (sum > 11 && sum < 11.1 ? 0 : 1);
- assert(ret == 0);
- return ret;
- }
- //] [/lexical_cast_variant_to_long_double]
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