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2d7ffed101
- Add an "Acknowledgements" section - Rename Boost.Hana to Hana for now (not officially a Boost library) - Partially write the section on "Introspection" Fixes #46 I feel like the documentation now provides enough real world examples: - switchAny - Euclidean distance - JSON generation (to be written) - MPL reimplementation
47 lines
1007 B
C++
47 lines
1007 B
C++
/*
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@copyright Louis Dionne 2015
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#include <boost/hana.hpp>
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#include <string>
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#include <vector>
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using namespace boost::hana;
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struct yes { std::string toString() const { return "yes"; } };
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struct no { };
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//! [optionalToString.sfinae]
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template <typename T>
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std::string optionalToString(T const& obj) {
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auto maybe_toString = sfinae([](auto&& x) -> decltype(x.toString()) {
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return x.toString();
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});
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return from_maybe("toString not defined", maybe_toString(obj));
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}
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//! [optionalToString.sfinae]
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int main() {
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BOOST_HANA_RUNTIME_CHECK(optionalToString(yes{}) == "yes");
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BOOST_HANA_RUNTIME_CHECK(optionalToString(no{}) == "toString not defined");
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{
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//! [maybe_add]
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auto maybe_add = sfinae([](auto x, auto y) -> decltype(x + y) {
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return x + y;
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});
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maybe_add(1, 2); // just(3)
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std::vector<int> v;
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maybe_add(v, "foobar"); // nothing
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//! [maybe_add]
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}
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}
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