From bb4854fca80cc20f0ebd60bfae2557d7c754073e Mon Sep 17 00:00:00 2001
From: Recolic Keghart <root@recolic.net>
Date: Wed, 11 Aug 2021 10:54:18 +0000
Subject: [PATCH] bug fix for rlib::printable_iter, to allow object that only
has nonconst begin() to get printable_iter
---
require/cxx20 | 12 ++++++++++++
stdio.hpp | 49 +++++++++++++++++++++++++++++-----------------
test/src/common.cc | 7 ++++++-
3 files changed, 49 insertions(+), 19 deletions(-)
create mode 100644 require/cxx20
diff --git a/require/cxx20 b/require/cxx20
new file mode 100644
index 0000000..8202250
--- /dev/null
+++ b/require/cxx20
@@ -0,0 +1,12 @@
+#ifndef R_CXX20_REQUIRED
+#define R_CXX20_REQUIRED
+
+#include <rlib/sys/os.hpp>
+
+#if RLIB_CXX_STD <= 2017
+#error This file requires compiler and library support \
+for the ISO C++ 2020 standard. This support must be enabled \
+with the -std=c++20 or -std=c++2a compiler options.
+#endif
+
+#endif
diff --git a/stdio.hpp b/stdio.hpp
index cdc028a..ced54db 100644
--- a/stdio.hpp
+++ b/stdio.hpp
@@ -102,19 +102,22 @@ namespace rlib {
template <typename Iterable, typename Printable>
struct _printable_iterable : private std::pair<Iterable, Printable> {
using std::pair<Iterable, Printable>::pair;
- const Iterable &arg() const {return std::pair<Iterable, Printable>::first;}
- const Printable &spliter() const {return std::pair<Iterable, Printable>::second;}
+ using _printable_iterable_tag = void;
+ Iterable &arg() & {return std::pair<Iterable, Printable>::first;}
+ Printable &spliter() & {return std::pair<Iterable, Printable>::second;}
+ Iterable &&arg() && {return std::pair<Iterable, Printable>::first;}
+ Printable &&spliter() && {return std::pair<Iterable, Printable>::second;}
+ const Iterable &arg() const & {return std::pair<Iterable, Printable>::first;}
+ const Printable &spliter() const & {return std::pair<Iterable, Printable>::second;}
};
+ template <typename FirstT, typename SecondT> using FirstOf = FirstT;
}
- // 2 more interfaces...
- template <typename Iterable, typename Printable>
- const impl::_printable_iterable<Iterable, Printable> printable_iter(Iterable arg, Printable spliter) {
- return impl::_printable_iterable<Iterable, Printable>(arg, spliter);
- }
- template <typename Iterable>
- const impl::_printable_iterable<Iterable, char> printable_iter(Iterable arg) {
- return impl::_printable_iterable<Iterable, char>(arg, ' ');
+ // more interfaces...
+ template <typename Iterable, typename Printable = char>
+ auto printable_iter(Iterable &&arg, Printable spliter = ' ') -> impl::_printable_iterable<typename std::decay<Iterable>::type, Printable> {
+ // TODO: avoid the extra copy while passing lvalue reference on constructing return value obj.
+ return impl::_printable_iterable<typename std::decay<Iterable>::type, Printable>(std::forward<Iterable>(arg), spliter);
}
inline bool sync_with_stdio(bool sync = true) noexcept {
@@ -124,8 +127,8 @@ namespace rlib {
return impl::enable_endl_flush() = enable;
}
-// Implements.
- template < class CharT, class Traits >
+ // Implements below ---------------------
+ template <typename CharT, typename Traits>
inline std::basic_ostream<CharT, Traits>& endl(std::basic_ostream<CharT, Traits>& os) {
os << RLIB_IMPL_ENDLINE;
if(impl::enable_endl_flush())
@@ -215,12 +218,22 @@ namespace rlib {
}
} // end namespace rlib
-template <typename Iterable, typename Printable>
-std::ostream& operator<< (std::ostream& stream, const rlib::impl::_printable_iterable<Iterable, Printable> &p) {
- for(auto val : p.arg()) {
- stream << val << p.spliter();
- }
- return stream;
+// auto-deduct const/nonconst left/right value ref.
+// For C++20 std::view, it doesn't have a `begin()` method for const lvalue ref. So we have to support
+// passing rvalue from rlib::printable_iter() to rlib::impl::_printable_iterable to operator<<
+// Instead of writing 3 overloads here, let us deduce automatically.
+template <typename PrintableIterableT>
+rlib::impl::FirstOf<std::ostream&, typename std::decay<PrintableIterableT>::type::_printable_iterable_tag> operator<< (std::ostream& stream, PrintableIterableT &&p) {
+ for(auto val : p.arg())
+ stream << val << p.spliter();
+ return stream;
}
+// // Old version, for backup
+// template <typename Iterable, typename Printable>
+// std::ostream& operator<< (std::ostream& stream, rlib::impl::_printable_iterable<Iterable, Printable> &&p) {
+// for(auto val : p.arg())
+// stream << val << p.spliter();
+// return stream;
+// }
#endif
diff --git a/test/src/common.cc b/test/src/common.cc
index 183c976..946908f 100644
--- a/test/src/common.cc
+++ b/test/src/common.cc
@@ -82,7 +82,12 @@ TEST_CASE("stdio.hpp") {
std::stringstream ss1, ss2;
rlib::println(ss1, rlib::printable_iter(v, rlib::printable_iter(v)));
rlib::print(ss2, rlib::printable_iter(v, rlib::printable_iter(v)));
- rlib::println(ss1.str() == answer + '\n', ss2.str() == answer);
+ rlib::println(ss1.str() == answer + RLIB_IMPL_ENDLINE, ss2.str() == answer);
+
+ const rlib_test_iterable vc{1.2, 6.666, 12, -11.11};
+ std::stringstream ssvc;
+ rlib::println(ssvc, rlib::printable_iter(vc, rlib::printable_iter(vc)));
+ REQUIRE(ssvc.str() == answer + RLIB_IMPL_ENDLINE);
}
--
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