258 lines
8.3 KiB
C++
258 lines
8.3 KiB
C++
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/*
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@file
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Defines `boost::hana::experimental::print`.
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@copyright Louis Dionne 2013-2016
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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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#ifndef BOOST_HANA_EXPERIMENTAL_PRINTABLE_HPP
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#define BOOST_HANA_EXPERIMENTAL_PRINTABLE_HPP
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#include <boost/hana/concept/constant.hpp>
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#include <boost/hana/concept/product.hpp>
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#include <boost/hana/concept/sequence.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/to.hpp>
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#include <boost/hana/core/dispatch.hpp>
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#include <boost/hana/first.hpp>
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#include <boost/hana/for_each.hpp>
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#include <boost/hana/intersperse.hpp>
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#include <boost/hana/second.hpp>
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#include <boost/hana/transform.hpp>
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#include <boost/hana/tuple.hpp>
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// models for different containers
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#include <boost/hana/fwd/map.hpp>
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#include <boost/hana/fwd/optional.hpp>
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#include <boost/hana/fwd/set.hpp>
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#include <boost/hana/fwd/string.hpp>
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#include <boost/hana/fwd/type.hpp>
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#include <boost/core/demangle.hpp>
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#include <iostream>
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#include <regex>
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#include <sstream>
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#include <string>
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#include <typeinfo>
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#include <utility>
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BOOST_HANA_NAMESPACE_BEGIN namespace experimental {
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template <typename T>
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struct Printable;
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//! @cond
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template <typename T, typename = void>
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struct print_impl : print_impl<T, hana::when<true>> { };
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template <typename T, bool condition>
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struct print_impl<T, hana::when<condition>> : hana::default_ {
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template <typename ...Args>
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static constexpr auto apply(Args&& ...) = delete;
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};
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//! @endcond
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//! @ingroup group-experimental
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//! Returns a string representation of the given object.
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//!
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//! This function is defined for most containers provided by Hana, and
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//! also for objects that define an `operator<<` that can be used with
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//! a `std::basic_ostream`. It can recursively print containers within
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//! containers, but do not expect any kind of proper indentation.
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//!
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//! This function requires (the rest of) Boost to be available on the
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//! system. It also requires RTTI to be enabled.
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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auto print = [](auto const& x) -> std::string {
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return tag-dispatched;
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};
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#else
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struct print_t {
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template <typename T>
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std::string operator()(T const& t) const {
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using Tag = typename hana::tag_of<T>::type;
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using Print = BOOST_HANA_DISPATCH_IF(print_impl<Tag>,
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hana::experimental::Printable<Tag>::value
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);
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#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
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static_assert(hana::experimental::Printable<Tag>::value,
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"hana::experimental::print(t) requires 't' to be Printable");
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#endif
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return Print::apply(t);
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}
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};
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constexpr print_t print{};
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#endif
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// Define the `Printable` concept
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template <typename T>
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struct Printable {
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using Tag = typename hana::tag_of<T>::type;
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static constexpr bool value = !hana::is_default<print_impl<Tag>>::value;
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};
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namespace print_detail {
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std::string strip_type_junk(std::string const& str) {
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return std::regex_replace(str, std::regex("^([a-z_]+::)*([a-z_]*)_t<"), "$2<");
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}
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}
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// model for Sequences
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template <typename S>
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struct print_impl<S, hana::when<hana::Sequence<S>::value>> {
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template <typename Xs>
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static std::string apply(Xs const& xs) {
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std::string result = "(";
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auto comma_separated = hana::intersperse(xs, ", ");
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hana::for_each(comma_separated, [&result](auto const& x) {
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result += hana::experimental::print(x);
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});
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result += ")";
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return result;
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}
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};
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// model for OutputStreamable types
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//! @cond
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template <typename S>
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struct print_impl<S, hana::when_valid<decltype(
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std::declval<std::ostringstream&>() << std::declval<S const&>()
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)>> {
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template <typename T>
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static std::string apply(T const& t) {
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std::ostringstream os;
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os << t;
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return os.str();
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}
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};
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//! @endcond
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// model for hana::optional
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template <>
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struct print_impl<hana::optional_tag> {
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template <typename O>
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static std::string apply(O const& optional) {
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return hana::maybe("nothing",
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[](auto const& x) {
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return "just(" + hana::experimental::print(x) + ")";
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}, optional);
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}
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};
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// model for hana::maps
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template <>
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struct print_impl<hana::map_tag> {
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template <typename M>
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static std::string apply(M const& map) {
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std::string result = "{";
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auto pairs = hana::transform(hana::to_tuple(map),
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[](auto const& pair) {
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return hana::experimental::print(hana::first(pair))
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+ " => "
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+ hana::experimental::print(hana::second(pair));
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});
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auto comma_separated = hana::intersperse(pairs, ", ");
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hana::for_each(comma_separated, [&result](auto const& element) {
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result += element;
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});
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result += "}";
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return result;
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}
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};
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// model for hana::metafunctions
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template <template <typename ...> class F>
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struct print_impl<hana::metafunction_t<F>> {
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template <typename T>
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static std::string apply(T const&) {
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return print_detail::strip_type_junk(boost::core::demangle(typeid(T).name()));
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}
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};
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// model for hana::metafunction_classes
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template <typename F>
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struct print_impl<hana::metafunction_class_t<F>> {
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template <typename T>
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static std::string apply(T const&) {
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return print_detail::strip_type_junk(boost::core::demangle(typeid(T).name()));
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}
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};
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// model for Constants holding a `Printable`
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template <typename C>
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struct print_impl<C, hana::when<
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hana::Constant<C>::value &&
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Printable<typename C::value_type>::value
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>> {
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template <typename T>
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static std::string apply(T const&) {
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constexpr auto value = hana::value<T>();
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return hana::experimental::print(value);
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}
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};
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// model for Products
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template <typename P>
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struct print_impl<P, hana::when<hana::Product<P>::value>> {
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template <typename T>
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static std::string apply(T const& t) {
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return '(' + hana::experimental::print(hana::first(t))
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+ ", "
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+ hana::experimental::print(hana::second(t)) + ')';
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}
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};
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// model for hana::strings
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template <>
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struct print_impl<hana::string_tag> {
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template <typename S>
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static std::string apply(S const& s) {
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return '"' + std::string{hana::to<char const*>(s)} + '"';
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}
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};
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// model for hana::sets
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template <>
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struct print_impl<hana::set_tag> {
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template <typename S>
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static std::string apply(S const& set) {
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std::string result = "{";
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auto as_tuple = hana::transform(hana::to_tuple(set),
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hana::experimental::print);
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auto comma_separated = hana::intersperse(as_tuple, ", ");
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hana::for_each(comma_separated, [&result](auto const& element) {
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result += element;
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});
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result += "}";
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return result;
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}
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};
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// model for hana::templates
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template <template <typename ...> class F>
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struct print_impl<template_t<F>> {
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template <typename T>
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static std::string apply(T const&) {
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return print_detail::strip_type_junk(boost::core::demangle(typeid(T).name()));
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}
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};
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// model for hana::types
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template <>
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struct print_impl<hana::type_tag> {
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template <typename T>
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static std::string apply(T const&) {
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using Type = typename T::type;
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return "type<" + boost::core::demangle(typeid(Type).name()) + '>';
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}
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};
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} BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_EXPERIMENTAL_PRINTABLE_HPP
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