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1 | /* |
2 | @file | |
3 | Defines `boost::hana::experimental::print`. | |
4 | ||
5 | @copyright Louis Dionne 2013-2016 | |
6 | Distributed under the Boost Software License, Version 1.0. | |
7 | (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) | |
8 | */ | |
9 | ||
10 | #ifndef BOOST_HANA_EXPERIMENTAL_PRINTABLE_HPP | |
11 | #define BOOST_HANA_EXPERIMENTAL_PRINTABLE_HPP | |
12 | ||
13 | #include <boost/hana/concept/constant.hpp> | |
14 | #include <boost/hana/concept/product.hpp> | |
15 | #include <boost/hana/concept/sequence.hpp> | |
16 | #include <boost/hana/config.hpp> | |
17 | #include <boost/hana/core/to.hpp> | |
18 | #include <boost/hana/core/dispatch.hpp> | |
19 | #include <boost/hana/first.hpp> | |
20 | #include <boost/hana/for_each.hpp> | |
21 | #include <boost/hana/intersperse.hpp> | |
22 | #include <boost/hana/second.hpp> | |
23 | #include <boost/hana/transform.hpp> | |
24 | #include <boost/hana/tuple.hpp> | |
25 | ||
26 | // models for different containers | |
27 | #include <boost/hana/fwd/map.hpp> | |
28 | #include <boost/hana/fwd/optional.hpp> | |
29 | #include <boost/hana/fwd/set.hpp> | |
30 | #include <boost/hana/fwd/string.hpp> | |
31 | #include <boost/hana/fwd/type.hpp> | |
32 | ||
33 | #include <boost/core/demangle.hpp> | |
34 | ||
35 | #include <iostream> | |
36 | #include <regex> | |
37 | #include <sstream> | |
38 | #include <string> | |
39 | #include <typeinfo> | |
40 | #include <utility> | |
41 | ||
42 | ||
43 | BOOST_HANA_NAMESPACE_BEGIN namespace experimental { | |
44 | template <typename T> | |
45 | struct Printable; | |
46 | ||
47 | //! @cond | |
48 | template <typename T, typename = void> | |
49 | struct print_impl : print_impl<T, hana::when<true>> { }; | |
50 | ||
51 | template <typename T, bool condition> | |
52 | struct print_impl<T, hana::when<condition>> : hana::default_ { | |
53 | template <typename ...Args> | |
54 | static constexpr auto apply(Args&& ...) = delete; | |
55 | }; | |
56 | //! @endcond | |
57 | ||
58 | //! @ingroup group-experimental | |
59 | //! Returns a string representation of the given object. | |
60 | //! | |
61 | //! This function is defined for most containers provided by Hana, and | |
62 | //! also for objects that define an `operator<<` that can be used with | |
63 | //! a `std::basic_ostream`. It can recursively print containers within | |
64 | //! containers, but do not expect any kind of proper indentation. | |
65 | //! | |
66 | //! This function requires (the rest of) Boost to be available on the | |
67 | //! system. It also requires RTTI to be enabled. | |
68 | #ifdef BOOST_HANA_DOXYGEN_INVOKED | |
69 | auto print = [](auto const& x) -> std::string { | |
70 | return tag-dispatched; | |
71 | }; | |
72 | #else | |
73 | struct print_t { | |
74 | template <typename T> | |
75 | std::string operator()(T const& t) const { | |
76 | using Tag = typename hana::tag_of<T>::type; | |
77 | using Print = BOOST_HANA_DISPATCH_IF(print_impl<Tag>, | |
78 | hana::experimental::Printable<Tag>::value | |
79 | ); | |
80 | ||
81 | #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS | |
82 | static_assert(hana::experimental::Printable<Tag>::value, | |
83 | "hana::experimental::print(t) requires 't' to be Printable"); | |
84 | #endif | |
85 | ||
86 | return Print::apply(t); | |
87 | } | |
88 | }; | |
89 | ||
90 | constexpr print_t print{}; | |
91 | #endif | |
92 | ||
93 | // Define the `Printable` concept | |
94 | template <typename T> | |
95 | struct Printable { | |
96 | using Tag = typename hana::tag_of<T>::type; | |
97 | static constexpr bool value = !hana::is_default<print_impl<Tag>>::value; | |
98 | }; | |
99 | ||
100 | namespace print_detail { | |
101 | std::string strip_type_junk(std::string const& str) { | |
102 | return std::regex_replace(str, std::regex("^([a-z_]+::)*([a-z_]*)_t<"), "$2<"); | |
103 | } | |
104 | } | |
105 | ||
106 | // model for Sequences | |
107 | template <typename S> | |
108 | struct print_impl<S, hana::when<hana::Sequence<S>::value>> { | |
109 | template <typename Xs> | |
110 | static std::string apply(Xs const& xs) { | |
111 | std::string result = "("; | |
112 | auto comma_separated = hana::intersperse(xs, ", "); | |
113 | hana::for_each(comma_separated, [&result](auto const& x) { | |
114 | result += hana::experimental::print(x); | |
115 | }); | |
116 | result += ")"; | |
117 | return result; | |
118 | } | |
119 | }; | |
120 | ||
121 | // model for OutputStreamable types | |
122 | //! @cond | |
123 | template <typename S> | |
124 | struct print_impl<S, hana::when_valid<decltype( | |
125 | std::declval<std::ostringstream&>() << std::declval<S const&>() | |
126 | )>> { | |
127 | template <typename T> | |
128 | static std::string apply(T const& t) { | |
129 | std::ostringstream os; | |
130 | os << t; | |
131 | return os.str(); | |
132 | } | |
133 | }; | |
134 | //! @endcond | |
135 | ||
136 | // model for hana::optional | |
137 | template <> | |
138 | struct print_impl<hana::optional_tag> { | |
139 | template <typename O> | |
140 | static std::string apply(O const& optional) { | |
141 | return hana::maybe("nothing", | |
142 | [](auto const& x) { | |
143 | return "just(" + hana::experimental::print(x) + ")"; | |
144 | }, optional); | |
145 | } | |
146 | }; | |
147 | ||
148 | // model for hana::maps | |
149 | template <> | |
150 | struct print_impl<hana::map_tag> { | |
151 | template <typename M> | |
152 | static std::string apply(M const& map) { | |
153 | std::string result = "{"; | |
154 | auto pairs = hana::transform(hana::to_tuple(map), | |
155 | [](auto const& pair) { | |
156 | return hana::experimental::print(hana::first(pair)) | |
157 | + " => " | |
158 | + hana::experimental::print(hana::second(pair)); | |
159 | }); | |
160 | auto comma_separated = hana::intersperse(pairs, ", "); | |
161 | hana::for_each(comma_separated, [&result](auto const& element) { | |
162 | result += element; | |
163 | }); | |
164 | result += "}"; | |
165 | return result; | |
166 | } | |
167 | }; | |
168 | ||
169 | // model for hana::metafunctions | |
170 | template <template <typename ...> class F> | |
171 | struct print_impl<hana::metafunction_t<F>> { | |
172 | template <typename T> | |
173 | static std::string apply(T const&) { | |
174 | return print_detail::strip_type_junk(boost::core::demangle(typeid(T).name())); | |
175 | } | |
176 | }; | |
177 | ||
178 | // model for hana::metafunction_classes | |
179 | template <typename F> | |
180 | struct print_impl<hana::metafunction_class_t<F>> { | |
181 | template <typename T> | |
182 | static std::string apply(T const&) { | |
183 | return print_detail::strip_type_junk(boost::core::demangle(typeid(T).name())); | |
184 | } | |
185 | }; | |
186 | ||
187 | // model for Constants holding a `Printable` | |
188 | template <typename C> | |
189 | struct print_impl<C, hana::when< | |
190 | hana::Constant<C>::value && | |
191 | Printable<typename C::value_type>::value | |
192 | >> { | |
193 | template <typename T> | |
194 | static std::string apply(T const&) { | |
195 | constexpr auto value = hana::value<T>(); | |
196 | return hana::experimental::print(value); | |
197 | } | |
198 | }; | |
199 | ||
200 | // model for Products | |
201 | template <typename P> | |
202 | struct print_impl<P, hana::when<hana::Product<P>::value>> { | |
203 | template <typename T> | |
204 | static std::string apply(T const& t) { | |
205 | return '(' + hana::experimental::print(hana::first(t)) | |
206 | + ", " | |
207 | + hana::experimental::print(hana::second(t)) + ')'; | |
208 | } | |
209 | }; | |
210 | ||
211 | // model for hana::strings | |
212 | template <> | |
213 | struct print_impl<hana::string_tag> { | |
214 | template <typename S> | |
215 | static std::string apply(S const& s) { | |
216 | return '"' + std::string{hana::to<char const*>(s)} + '"'; | |
217 | } | |
218 | }; | |
219 | ||
220 | // model for hana::sets | |
221 | template <> | |
222 | struct print_impl<hana::set_tag> { | |
223 | template <typename S> | |
224 | static std::string apply(S const& set) { | |
225 | std::string result = "{"; | |
226 | auto as_tuple = hana::transform(hana::to_tuple(set), | |
227 | hana::experimental::print); | |
228 | auto comma_separated = hana::intersperse(as_tuple, ", "); | |
229 | hana::for_each(comma_separated, [&result](auto const& element) { | |
230 | result += element; | |
231 | }); | |
232 | result += "}"; | |
233 | return result; | |
234 | } | |
235 | }; | |
236 | ||
237 | // model for hana::templates | |
238 | template <template <typename ...> class F> | |
239 | struct print_impl<template_t<F>> { | |
240 | template <typename T> | |
241 | static std::string apply(T const&) { | |
242 | return print_detail::strip_type_junk(boost::core::demangle(typeid(T).name())); | |
243 | } | |
244 | }; | |
245 | ||
246 | // model for hana::types | |
247 | template <> | |
248 | struct print_impl<hana::type_tag> { | |
249 | template <typename T> | |
250 | static std::string apply(T const&) { | |
251 | using Type = typename T::type; | |
252 | return "type<" + boost::core::demangle(typeid(Type).name()) + '>'; | |
253 | } | |
254 | }; | |
255 | } BOOST_HANA_NAMESPACE_END | |
256 | ||
257 | #endif // !BOOST_HANA_EXPERIMENTAL_PRINTABLE_HPP |