[PATCH 2/2] libstdc++: Optimize operator<< for piecewise distributions.

[Tomasz Kamiński]

This avoids creating an temporary vector and uses _M_int and _M_den
members of _M_param. Empty _M_int (default) values are handled by
printing values direclty.

libstdc++-v3/ChangeLog:

	* include/bits/random.h	(piecewise_constant_distribution::param_type)
	(piecewise_linear_distribution::param_type): Befriend operator<<.
	* include/bits/random.tcc
	(operator<<(basic_ostream&, piecewise_linear_distribution)
	(operator<<(basic_ostream&, piecewise_constant_distribution):
	Use __x._M_param._M_int and __x._M_param._M_den instead of accessors.
---
In addition to avoid allocating a temporary vectors, this output the
type stored in _M_den vector, even if the signature of interface changes.
And also gives a choice of the output, with simple replacements of auto
in for each loop.

Testing on x86_64-linux. All *piecewise* test already passed.
OK for trunk when all test passes?

 libstdc++-v3/include/bits/random.h   | 10 +++++++
 libstdc++-v3/include/bits/random.tcc | 44 ++++++++++++++++------------
 2 files changed, 36 insertions(+), 18 deletions(-)

diff --git a/libstdc++-v3/include/bits/random.h b/libstdc++-v3/include/bits/random.h
index 5d037465d3c..a0592a00763 100644
--- a/libstdc++-v3/include/bits/random.h
+++ b/libstdc++-v3/include/bits/random.h
@@ -6474,6 +6474,11 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
 	std::vector<_RealType> _M_int;
 	std::vector<double> _M_den;
 	std::vector<double> _M_cp;
+
+	template<typename _RealType1, typename _CharT, typename _Traits>
+	  friend std::basic_ostream<_CharT, _Traits>&
+	  operator<<(std::basic_ostream<_CharT, _Traits>&,
+		     const std::piecewise_constant_distribution<_RealType1>&);
       };
 
       piecewise_constant_distribution()
@@ -6758,6 +6763,11 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
 	std::vector<double> _M_den;
 	std::vector<double> _M_cp;
 	std::vector<double> _M_m;
+
+	template<typename _RealType1, typename _CharT, typename _Traits>
+	  friend std::basic_ostream<_CharT, _Traits>&
+	  operator<<(std::basic_ostream<_CharT, _Traits>&,
+		     const std::piecewise_linear_distribution<_RealType1>&);
       };
 
       piecewise_linear_distribution()
diff --git a/libstdc++-v3/include/bits/random.tcc b/libstdc++-v3/include/bits/random.tcc
index 80b51d099fa..e581f912764 100644
--- a/libstdc++-v3/include/bits/random.tcc
+++ b/libstdc++-v3/include/bits/random.tcc
@@ -3173,15 +3173,19 @@ namespace __detail
       __os.fill(__space);
       __os.precision(std::numeric_limits<_RealType>::max_digits10);
 
-      std::vector<_RealType> __int = __x.intervals();
-      __os << __int.size() - 1;
-
-      for (auto __xit = __int.begin(); __xit != __int.end(); ++__xit)
-	__os << __space << *__xit;
-
-      std::vector<double> __den = __x.densities();
-      for (auto __dit = __den.begin(); __dit != __den.end(); ++__dit)
-	__os << __space << *__dit;
+      const auto& __int = __x._M_param._M_int;
+      if (__int.empty())
+	__os << size_t(1)
+	     << __space << _RealType(0) << __space << _RealType(1)
+	     << __space << _RealType(1);
+      else
+	{
+	  __os << __int.size() - 1;
+	  for (auto __xv : __int)
+	    __os << __space << __xv;
+	  for (auto __dv : __x._M_param._M_den)
+	    __os << __space << __dv;
+	}
 
       __os.flags(__flags);
       __os.fill(__fill);
@@ -3436,15 +3440,19 @@ namespace __detail
       __os.fill(__space);
       __os.precision(std::numeric_limits<_RealType>::max_digits10);
 
-      std::vector<_RealType> __int = __x.intervals();
-      __os << __int.size() - 1;
-
-      for (auto __xit = __int.begin(); __xit != __int.end(); ++__xit)
-	__os << __space << *__xit;
-
-      std::vector<double> __den = __x.densities();
-      for (auto __dit = __den.begin(); __dit != __den.end(); ++__dit)
-	__os << __space << *__dit;
+      auto const& __int = __x._M_param._M_int;
+      if (__int.empty())
+	__os << size_t(1)
+	     << __space << _RealType(0) << __space << _RealType(1)
+	     << __space << _RealType(1) << __space << _RealType(1);
+      else
+	{
+	  __os << __int.size() - 1;
+	  for (auto __xv : __int)
+	    __os << __space << __xv;
+	  for (auto __dv : __x._M_param._M_den)
+	    __os << __space << __dv;
+	}
 
       __os.flags(__flags);
       __os.fill(__fill);
-- 
2.54.0