Merge pull request #122 from boostorg/hexadecimal

Print float128 as hexadecimal floating point literals if the ios_base…
boostorg · Apr 12, 2019 · de3ab81 · de3ab81
2 parents c062629 + 32628fb
commit de3ab81
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Showing 2 changed files with 37 additions and 4 deletions.
diff --git a/include/boost/multiprecision/float128.hpp b/include/boost/multiprecision/float128.hpp
@@ -264,8 +264,7 @@ struct float128_backend
    std::string str(std::streamsize digits, std::ios_base::fmtflags f)const
    {
 #ifndef BOOST_MP_USE_QUAD
-      char buf[100];
-      boost::scoped_array<char> buf2;
+      char buf[128];
       std::string format = "%";
       if(f & std::ios_base::showpos)
          format += "+";
@@ -275,18 +274,25 @@ struct float128_backend
       if(digits == 0)
          digits = 36;
       format += "Q";
+
       if(f & std::ios_base::scientific)
          format += "e";
       else if(f & std::ios_base::fixed)
          format += "f";
       else
          format += "g";
 
-      int v = quadmath_snprintf (buf, 100, format.c_str(), digits, m_value);
+      int v;
+      if ((f & std::ios_base::scientific) && (f & std::ios_base::fixed) ) {
+         v = quadmath_snprintf (buf, sizeof buf, "%Qa", m_value);
+      } else {
+         v = quadmath_snprintf (buf, sizeof buf, format.c_str(), digits, m_value);
+      }
 
-      if((v < 0) || (v >= 99))
+      if((v < 0) || (v >= 127))
       {
          int v_max = v;
+         boost::scoped_array<char> buf2;
          buf2.reset(new char[v+3]);
          v = quadmath_snprintf (&buf2[0], v_max + 3, format.c_str(), digits, m_value);
          if(v >= v_max + 3)

diff --git a/test/test_float_io.cpp b/test/test_float_io.cpp
@@ -300,6 +300,32 @@ void test_round_trip()
    }
 }
 
+#ifdef TEST_FLOAT128
+void test_hexadecimal_floating_point()
+{
+   using boost::multiprecision::float128;
+
+   float128 x = 0x1p+0Q;
+
+   std::string s = x.str(0, std::ios_base::fmtflags(std::ios_base::fixed | std::ios_base::scientific));
+   BOOST_CHECK_EQUAL(s, "0x1p+0");
+
+   s = x.str(0, std::ios_base::fmtflags(std::ios_base::floatfield));
+   BOOST_CHECK_EQUAL(s, "0x1p+0");
+
+   x = -1;
+   s = x.str(0, std::ios_base::fmtflags(std::ios_base::floatfield));
+   BOOST_CHECK_EQUAL(s, "-0x1p+0");
+
+   // hexadecimal representation of pi; test a round trip:
+   float128 pi1 = 0x1.921fb54442d18469898cc51701b8p+1Q;
+   s = pi1.str(0, std::ios_base::fmtflags(std::ios_base::floatfield));
+   float128 pi2(s);
+   BOOST_CHECK_EQUAL(pi1, pi2);
+
+}
+#endif
+
 int main()
 {
 #ifdef TEST_MPFR_50
@@ -336,6 +362,7 @@ int main()
 #endif
 #ifdef TEST_FLOAT128
    test<boost::multiprecision::float128>();
+   test_hexadecimal_floating_point();
 #ifndef BOOST_INTEL
    test_round_trip<boost::multiprecision::float128>();
 #endif