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