docs: Fix link in README

Bump the release note to the latest version

.github/workflows/build.yml

@@ -1,7 +1,7 @@
 name: Github PR
 on:
   push:
-    branches: [ master, merge-key-support ]
+    branches: [ master ]
   pull_request:
     branches: [ master ]
   workflow_dispatch:
@@ -40,7 +40,7 @@ jobs:
           ${{format(matrix.generator != 'Default Generator' && '-G "{0}"' || '', matrix.generator)}}
         CMAKE_INSTALL_PREFIX: "${{ github.workspace }}/install-prefix"
         CMAKE_BUILD_TYPE: Debug
-        CMAKE_CXX_FLAGS_DEBUG: ${{ matrix.googletest == 'build' && '-g -D_GLIBCXX_DEBUG -D_GLIBCXX_DEBUG_PEDANTIC' || '-g' }}
+        CMAKE_CXX_FLAGS_DEBUG: ${{ matrix.googletest == 'build' && '-g -D_GLIBCXX_DEBUG -D_GLIBCXX_DEBUG_PEDANTIC' || '-g' }} 
       runs-on: ${{ matrix.os }}
       steps:
 
@@ -64,8 +64,7 @@ jobs:
               -D CMAKE_CXX_FLAGS_DEBUG="${{ env.CMAKE_CXX_FLAGS_DEBUG }}" \
               -D YAML_BUILD_SHARED_LIBS=${{ env.YAML_BUILD_SHARED_LIBS }} \
               -D YAML_USE_SYSTEM_GTEST=${{ env.YAML_USE_SYSTEM_GTEST }} \
-              -D YAML_CPP_BUILD_TESTS=ON \
-              -DYAML_CPP_SUPPORT_MERGE_KEYS=ON
+              -D YAML_CPP_BUILD_TESTS=ON
 
         - name: Build
           run: |

CMakeLists.txt

@@ -29,7 +29,6 @@ option(YAML_CPP_FORMAT_SOURCE "Format source" ${YAML_CPP_MAIN_PROJECT})
 option(YAML_CPP_DISABLE_UNINSTALL  "Disable uninstallation of yaml-cpp" OFF)
 option(YAML_USE_SYSTEM_GTEST "Use system googletest if found" OFF)
 option(YAML_ENABLE_PIC "Use Position-Independent Code " ON)
-option(YAML_CPP_SUPPORT_MERGE_KEYS "Support YAML merge keys ('<<') in yaml-cpp's executable targets. Use '#define YAML_CPP_SUPPORT_MERGE_KEYS' instead when linking from another project." OFF)
 
 cmake_dependent_option(YAML_CPP_BUILD_TESTS
   "Enable yaml-cpp tests" OFF
@@ -39,7 +38,7 @@ cmake_dependent_option(YAML_MSVC_SHARED_RT
   "CMAKE_SYSTEM_NAME MATCHES Windows" OFF)
 set(YAML_CPP_INSTALL_CMAKEDIR "${CMAKE_INSTALL_LIBDIR}/cmake/yaml-cpp"
   CACHE STRING "Path to install the CMake package to")
-
+ 
 if (YAML_CPP_FORMAT_SOURCE)
     find_program(YAML_CPP_CLANG_FORMAT_EXE NAMES clang-format)
 endif()
@@ -134,8 +133,7 @@ target_compile_definitions(yaml-cpp
     $<$<NOT:$<BOOL:${YAML_BUILD_SHARED_LIBS}>>:YAML_CPP_STATIC_DEFINE>
   PRIVATE
     $<${build-windows-dll}:${PROJECT_NAME}_DLL>
-    $<$<NOT:$<BOOL:${YAML_CPP_BUILD_CONTRIB}>>:YAML_CPP_NO_CONTRIB>
-    $<$<BOOL:${YAML_CPP_SUPPORT_MERGE_KEYS}>:YAML_CPP_SUPPORT_MERGE_KEYS>)
+    $<$<NOT:$<BOOL:${YAML_CPP_BUILD_CONTRIB}>>:YAML_CPP_NO_CONTRIB>)
 
 target_sources(yaml-cpp
   PRIVATE

include/yaml-cpp/emitter.h

@@ -26,6 +26,7 @@
 #include "yaml-cpp/emittermanip.h"
 #include "yaml-cpp/null.h"
 #include "yaml-cpp/ostream_wrapper.h"
+#include "yaml-cpp/fptostring.h"
 
 namespace YAML {
 class Binary;
@@ -186,7 +187,7 @@ inline Emitter& Emitter::WriteStreamable(T value) {
   }
 
   if (!special) {
-    stream << value;
+    stream << FpToString(value, stream.precision());
   }
   m_stream << stream.str();
 

include/yaml-cpp/fptostring.h

@@ -0,0 +1,15 @@
+#ifndef YAML_H_FPTOSTRING
+#define YAML_H_FPTOSTRING
+
+#include "yaml-cpp/dll.h"
+
+#include <string>
+
+namespace YAML {
+// "precision = 0" refers to shortest known unique representation of the value
+YAML_CPP_API std::string FpToString(float v, size_t precision = 0);
+YAML_CPP_API std::string FpToString(double v, size_t precision = 0);
+YAML_CPP_API std::string FpToString(long double v, size_t precision = 0);
+}
+
+#endif

include/yaml-cpp/node/convert.h

@@ -28,6 +28,7 @@
 #include "yaml-cpp/node/node.h"
 #include "yaml-cpp/node/type.h"
 #include "yaml-cpp/null.h"
+#include "yaml-cpp/fptostring.h"
 
 
 namespace YAML {
@@ -129,7 +130,7 @@ inner_encode(const T& rhs, std::stringstream& stream){
       stream << ".inf";
     }
   } else {
-    stream << rhs;
+    stream << FpToString(rhs, stream.precision());
   }
 }
 

include/yaml-cpp/node/detail/node.h

@@ -128,23 +128,12 @@ class node {
     // NOTE: this returns a non-const node so that the top-level Node can wrap
     // it, and returns a pointer so that it can be nullptr (if there is no such
     // key).
-    node* value = static_cast<const node_ref&>(*m_pRef).get(key, pMemory);
-#ifdef YAML_CPP_SUPPORT_MERGE_KEYS
-    if (!value || value->type() == NodeType::Undefined) {
-      return get_value_from_merge_key(key, value, pMemory);
-    }
-#endif
-    return value;
+    return static_cast<const node_ref&>(*m_pRef).get(key, pMemory);
   }
   template <typename Key>
   node& get(const Key& key, shared_memory_holder pMemory) {
     node& value = m_pRef->get(key, pMemory);
     value.add_dependency(*this);
-#ifdef YAML_CPP_SUPPORT_MERGE_KEYS
-    if (value.type() == NodeType::Undefined) {
-      return *get_value_from_merge_key(key, &value, pMemory);
-    }
-#endif
     return value;
   }
   template <typename Key>
@@ -176,33 +165,6 @@ class node {
   }
 
  private:
-#ifdef YAML_CPP_SUPPORT_MERGE_KEYS
-  template <typename Key>
-  inline node* get_value_from_merge_key(const Key& key, node* currentValue,
-                                        shared_memory_holder pMemory) const {
-    node* mergeValue =
-      static_cast<const node_ref&>(*m_pRef).get(std::string("<<"), pMemory);
-    if (!mergeValue) {
-      return currentValue;
-    }
-    if (mergeValue->type() == NodeType::Map) {
-      return &mergeValue->get(key, pMemory);
-    }
-    if (mergeValue->type() == NodeType::Sequence) {
-      for (const_node_iterator it = mergeValue->begin();
-            it != mergeValue->end(); ++it) {
-        if (it->pNode && it->pNode->type() == NodeType::Map) {
-          node* value = it->pNode->get(key, pMemory);
-          if (value && value->type() != NodeType::Undefined) {
-            return value;
-          }
-        }
-      }
-    }
-    return currentValue;
-  }
-#endif
-
   shared_node_ref m_pRef;
   using nodes = std::set<node*, less>;
   nodes m_dependencies;

src/fptostring.cpp

@@ -0,0 +1,238 @@
+#include "yaml-cpp/fptostring.h"
+#include "contrib/dragonbox.h"
+
+#include <array>
+#include <cassert>
+#include <cmath>
+#include <limits>
+#include <sstream>
+#include <tuple>
+
+namespace YAML {
+namespace detail {
+namespace fp_formatting {
+
+/**
+ * Converts a integer into its ASCII digits.
+ *
+ * @param begin/end - a buffer, must be at least 20bytes long.
+ * @param value     - input value.
+ * @param width     - minimum number of digits, fill with '0' to the left. Must be equal or smaller than the buffer size.
+ * @return          - number of digits filled into the buffer (or -1 if preconditions are not meet)
+ *
+ * Example:
+ * std::array<char, 20> buffer;
+ * auto ct = ConvertToChars(buffer.begin(), buffer.end(), 23, 3);
+ * assert(ct = 3);
+ * assert(buffer[0] == '0');
+ * assert(buffer[1] == '2');
+ * assert(buffer[2] == '3');
+ */
+int ConvertToChars(char* begin, char* end, size_t value, int width=1) {
+  // precondition of this function (will trigger in debug build)
+  assert(width >= 1);
+  assert(end >= begin);       // end must be after begin
+  assert(end-begin >= width); // Buffer must be large enough
+  assert(end-begin >= 20);    // 2^64 has 20digits, so at least 20 digits must be available
+
+  // defensive programming, abort if precondition are not met (will trigger in release build)
+  if (width < 1) {
+    return -1;
+  }
+  if (end < begin) {
+    return -1;
+  }
+  if (end-begin < width) {
+    return -1;
+  }
+  if (end-begin < 20) {
+    return -1;
+  }
+
+
+  // count number of digits, and fill digits array accordingly
+  int digits_ct{};
+  while (value > 0) {
+    char c = value % 10 + '0';
+    value = value / 10;
+    digits_ct += 1;
+    *(end-digits_ct) = c;
+  }
+  while(digits_ct < width) {
+    assert(digits_ct < 64);
+    digits_ct += 1;
+    *(end-digits_ct) = '0';
+  }
+  // move data to the front of the array
+  std::memmove(begin, end-digits_ct, digits_ct);
+  return digits_ct;
+}
+
+/**
+ * Converts a float or double to a string.
+ *
+ * converts a value 'v' to a string. Uses dragonbox for formatting.
+ */
+template <typename T>
+std::string FpToString(T v, int precision = 0) {
+  // hard coded constant, at which exponent should switch to a scientific notation
+  int const lowerExponentThreshold = -5;
+  int const upperExponentThreshold =  (precision==0)?6:precision;
+  if (precision == 0) {
+    precision = 6;
+  }
+
+  // dragonbox/to_decimal does not handle value 0, inf, NaN
+  if (v == 0 || std::isinf(v) || std::isnan(v)) {
+    std::stringstream ss;
+    ss.imbue(std::locale("C"));
+    ss << v;
+    return ss.str();
+  }
+
+  auto r = jkj::dragonbox::to_decimal(v);
+
+  auto digits  = std::array<char, 20>{}; // max digits of size_t is 20.
+  auto digits_ct = ConvertToChars(digits.data(), digits.data() + digits.size(), r.significand);
+
+  // defensive programming, ConvertToChars arguments are invalid
+  if (digits_ct == -1) {
+    std::stringstream ss;
+    ss.imbue(std::locale("C"));
+    ss << v;
+    return ss.str();
+  }
+
+  // check if requested precision is lower than
+  // required digits for exact representation
+  if (digits_ct > precision) {
+    auto diff = digits_ct - precision;
+    r.exponent += diff;
+    digits_ct = precision;
+
+    // round numbers if required
+    if (digits[digits_ct] >= '5') {
+      int i{digits_ct-1};
+      digits[i] += 1;
+      while (digits[i] == '9'+1) {
+        digits_ct -= 1;
+        r.exponent += 1;
+        if (i > 0) {
+          digits[i-1] += 1;
+          i -= 1;
+        } else {
+          digits_ct = 1;
+          digits[0] = '1';
+          break;
+        }
+      }
+    }
+  }
+
+  std::array<char, 28> output_buffer; // max digits of size_t plus sign, a dot and 2 letters for 'e+' or 'e-' and 4 letters for the exponent
+  auto output_ptr = &output_buffer[0];
+
+  // print '-' symbol for negative numbers
+  if (r.is_negative) {
+    *(output_ptr++) = '-';
+  }
+
+  // exponent if only a single non-zero digit is before the decimal point
+  int const exponent = r.exponent + digits_ct - 1;
+
+  // case 1: scientific notation
+  if (exponent >= upperExponentThreshold || exponent <= lowerExponentThreshold) {
+    // print first digit
+    *(output_ptr++) = digits[0];
+
+    // print digits after decimal point
+    if (digits_ct > 1) {
+      *(output_ptr++) = '.';
+      // print significant numbers after decimal point
+      for (int i{1}; i < digits_ct; ++i) {
+         *(output_ptr++) = digits[i];
+      }
+    }
+    *(output_ptr++) = 'e';
+    *(output_ptr++) = (exponent>=0)?'+':'-';
+    auto exp_digits = std::array<char, 20>{};
+    auto exp_digits_ct = ConvertToChars(exp_digits.data(), exp_digits.data() + exp_digits.size(), std::abs(exponent), /*.precision=*/ 2);
+
+    // defensive programming, ConvertToChars arguments are invalid
+    if (exp_digits_ct == -1) {
+      std::stringstream ss;
+      ss.imbue(std::locale("C"));
+      ss << v;
+      return ss.str();
+    }
+
+    for (int i{0}; i < exp_digits_ct; ++i) {
+      *(output_ptr++) = exp_digits[i];
+    }
+
+  // case 2: default notation
+  } else {
+    auto const digits_end   = digits.begin() + digits_ct;
+    auto digits_iter    = digits.begin();
+
+    // print digits before point
+    int const before_decimal_digits = digits_ct + r.exponent;
+    if (before_decimal_digits > 0) {
+      // print digits before point
+      for (int i{0}; i < std::min(before_decimal_digits, digits_ct); ++i) {
+        *(output_ptr++) = *(digits_iter++);
+      }
+      // print trailing zeros before point
+      for (int i{0}; i < before_decimal_digits - digits_ct; ++i) {
+        *(output_ptr++) = '0';
+      }
+
+    // print 0 before point if none where printed before
+    } else {
+      *(output_ptr++) = '0';
+    }
+
+    if (digits_iter != digits_end) {
+      *(output_ptr++) = '.';
+      // print 0 after decimal point, to fill until first digits
+      int const after_decimal_zeros = -digits_ct - r.exponent;
+      for (int i{0}; i < after_decimal_zeros; ++i) {
+         *(output_ptr++) = '0';
+      }
+
+      // print significant numbers after decimal point
+      for (;digits_iter < digits_end; ++digits_iter) {
+         *(output_ptr++) = *digits_iter;
+      }
+    }
+  }
+  *output_ptr = '\0';
+  return std::string{&output_buffer[0], output_ptr};
+}
+
+}
+}
+
+std::string FpToString(float v, size_t precision) {
+  return detail::fp_formatting::FpToString(v, precision);
+}
+
+std::string FpToString(double v, size_t precision) {
+  return detail::fp_formatting::FpToString(v, precision);
+}
+
+/**
+ * dragonbox only works for floats/doubles not long double
+ */
+std::string FpToString(long double v, size_t precision) {
+  std::stringstream ss;
+  ss.imbue(std::locale("C"));
+  if (precision == 0) {
+     precision = std::numeric_limits<long double>::max_digits10;
+  }
+  ss.precision(precision);
+  ss << v;
+  return ss.str();
+}
+
+}

test/CMakeLists.txt

@@ -41,9 +41,6 @@ target_compile_options(yaml-cpp-tests
   PRIVATE
     $<$<CXX_COMPILER_ID:Clang>:-Wno-c99-extensions -Wno-variadic-macros -Wno-sign-compare>
     $<$<CXX_COMPILER_ID:GNU>:-Wno-variadic-macros -Wno-sign-compare -Wno-narrowing>)
-target_compile_definitions(yaml-cpp-tests
-  PRIVATE
-    $<$<BOOL:${YAML_CPP_SUPPORT_MERGE_KEYS}>:YAML_CPP_SUPPORT_MERGE_KEYS>)
 target_link_libraries(yaml-cpp-tests
   PRIVATE
     Threads::Threads

test/fptostring_test.cpp

@@ -0,0 +1,242 @@
+#include "yaml-cpp/fptostring.h"
+#include "gtest/gtest.h"
+
+namespace YAML {
+namespace {
+
+/**
+ * Helper function, that converts double to string as std::stringstream would do
+ */
+template <typename T>
+static std::string convert_with_stringstream(T v, size_t precision = 0) {
+  std::stringstream ss;
+  if (precision > 0) {
+    ss << std::setprecision(precision);
+  }
+  ss << v;
+  return ss.str();
+}
+
+// Caution: Test involving 'convert_with_stringstream' are based on std::stringstream
+// having certain printing behavior, if these changes, the unit test might fail.
+// This is not a fault of FpToString just a weakness of the way these
+// tests are constructed
+
+TEST(FpToStringTest, conversion_double) {
+  // Issue motivating FpToString function,
+  // https://github.com/jbeder/yaml-cpp/issues/1289
+  // Original problem at hand:
+  EXPECT_EQ("34.34", FpToString(34.34));
+  EXPECT_EQ("56.56", FpToString(56.56));
+  EXPECT_EQ("12.12", FpToString(12.12));
+  EXPECT_EQ("78.78", FpToString(78.78));
+
+  // Special challenge with rounding
+  // https://github.com/jbeder/yaml-cpp/issues/1289#issuecomment-2211705536
+  EXPECT_EQ("1.54743e+26", FpToString(1.5474250491e+26f));
+  EXPECT_EQ(convert_with_stringstream(1.5474250491e+26f), FpToString(1.5474250491e+26f));
+  EXPECT_EQ("1.5474251e+26", FpToString(1.5474250491e+26f, 8));
+
+  // prints the same way as std::stringstream
+  EXPECT_EQ(convert_with_stringstream(1.), FpToString(1.));
+  EXPECT_EQ(convert_with_stringstream(1e0), FpToString(1e0));
+  EXPECT_EQ(convert_with_stringstream(1e1), FpToString(1e1));
+  EXPECT_EQ(convert_with_stringstream(1e2), FpToString(1e2));
+  EXPECT_EQ(convert_with_stringstream(1e3), FpToString(1e3));
+  EXPECT_EQ(convert_with_stringstream(1e4), FpToString(1e4));
+  EXPECT_EQ(convert_with_stringstream(1e5), FpToString(1e5));
+  EXPECT_EQ(convert_with_stringstream(1e6), FpToString(1e6));
+  EXPECT_EQ(convert_with_stringstream(1e7), FpToString(1e7));
+  EXPECT_EQ(convert_with_stringstream(1e8), FpToString(1e8));
+  EXPECT_EQ(convert_with_stringstream(1e9), FpToString(1e9));
+
+  // Print by default values below 1e6 without scientific notation
+  EXPECT_EQ("1", FpToString(1.));
+  EXPECT_EQ("1", FpToString(1e0));
+  EXPECT_EQ("10", FpToString(1e1));
+  EXPECT_EQ("100", FpToString(1e2));
+  EXPECT_EQ("1000", FpToString(1e3));
+  EXPECT_EQ("10000", FpToString(1e4));
+  EXPECT_EQ("100000", FpToString(1e5));
+  EXPECT_EQ("1e+06", FpToString(1e6));
+  EXPECT_EQ("1e+07", FpToString(1e7));
+  EXPECT_EQ("1e+08", FpToString(1e8));
+  EXPECT_EQ("1e+09", FpToString(1e9));
+
+  // prints the same way as std::stringstream
+  EXPECT_EQ(convert_with_stringstream(1.), FpToString(1.));
+  EXPECT_EQ(convert_with_stringstream(1e-0), FpToString(1e-0));
+  EXPECT_EQ(convert_with_stringstream(1e-1), FpToString(1e-1));
+  EXPECT_EQ(convert_with_stringstream(1e-2), FpToString(1e-2));
+  EXPECT_EQ(convert_with_stringstream(1e-3), FpToString(1e-3));
+  EXPECT_EQ(convert_with_stringstream(1e-4), FpToString(1e-4));
+  EXPECT_EQ(convert_with_stringstream(1e-5), FpToString(1e-5));
+  EXPECT_EQ(convert_with_stringstream(1e-6), FpToString(1e-6));
+  EXPECT_EQ(convert_with_stringstream(1e-7), FpToString(1e-7));
+  EXPECT_EQ(convert_with_stringstream(1e-8), FpToString(1e-8));
+  EXPECT_EQ(convert_with_stringstream(1e-9), FpToString(1e-9));
+
+  // Print by default values above 1e-5 without scientific notation
+  EXPECT_EQ("1", FpToString(1.));
+  EXPECT_EQ("1", FpToString(1e-0));
+  EXPECT_EQ("0.1", FpToString(1e-1));
+  EXPECT_EQ("0.01", FpToString(1e-2));
+  EXPECT_EQ("0.001", FpToString(1e-3));
+  EXPECT_EQ("0.0001", FpToString(1e-4));
+  EXPECT_EQ("1e-05", FpToString(1e-5));
+  EXPECT_EQ("1e-06", FpToString(1e-6));
+  EXPECT_EQ("1e-07", FpToString(1e-7));
+  EXPECT_EQ("1e-08", FpToString(1e-8));
+  EXPECT_EQ("1e-09", FpToString(1e-9));
+
+  // changing precision has the same effect as std::stringstream
+  EXPECT_EQ(convert_with_stringstream(123., 1), FpToString(123., 1));
+  EXPECT_EQ(convert_with_stringstream(1234567., 7), FpToString(1234567., 7));
+  EXPECT_EQ(convert_with_stringstream(12345.67, 7), FpToString(12345.67, 7));
+  EXPECT_EQ(convert_with_stringstream(1234567e-9, 7), FpToString(1234567e-9, 7));
+  EXPECT_EQ(convert_with_stringstream(1234567e-9, 1), FpToString(1234567e-9, 1));
+
+ // known example that is difficult to round
+  EXPECT_EQ("1", FpToString(0.9999, 2));
+  EXPECT_EQ("-1", FpToString(-0.9999, 2));
+
+  // some more random tests
+  EXPECT_EQ("1.25", FpToString(1.25));
+  EXPECT_EQ("34.34", FpToString(34.34));
+  EXPECT_EQ("1e+20", FpToString(1e+20));
+  EXPECT_EQ("1.1e+20", FpToString(1.1e+20));
+  EXPECT_EQ("1e-20", FpToString(1e-20));
+  EXPECT_EQ("1.1e-20", FpToString(1.1e-20));
+  EXPECT_EQ("1e-20", FpToString(0.1e-19));
+  EXPECT_EQ("1.1e-20", FpToString(0.11e-19));
+
+  EXPECT_EQ("19", FpToString(18.9, 2));
+  EXPECT_EQ("20", FpToString(19.9, 2));
+  EXPECT_EQ("2e+01", FpToString(19.9, 1));
+  EXPECT_EQ("1.2e-05", FpToString(1.234e-5, 2));
+  EXPECT_EQ("1.3e-05", FpToString(1.299e-5, 2));
+
+  EXPECT_EQ("-1", FpToString(-1.));
+  EXPECT_EQ("-1.25", FpToString(-1.25));
+  EXPECT_EQ("-34.34", FpToString(-34.34));
+  EXPECT_EQ("-1e+20", FpToString(-1e+20));
+  EXPECT_EQ("-1.1e+20", FpToString(-1.1e+20));
+  EXPECT_EQ("-1e-20", FpToString(-1e-20));
+  EXPECT_EQ("-1.1e-20", FpToString(-1.1e-20));
+  EXPECT_EQ("-1e-20", FpToString(-0.1e-19));
+  EXPECT_EQ("-1.1e-20", FpToString(-0.11e-19));
+
+  EXPECT_EQ("-19", FpToString(-18.9, 2));
+  EXPECT_EQ("-20", FpToString(-19.9, 2));
+  EXPECT_EQ("-2e+01", FpToString(-19.9, 1));
+  EXPECT_EQ("-1.2e-05", FpToString(-1.234e-5, 2));
+  EXPECT_EQ("-1.3e-05", FpToString(-1.299e-5, 2));
+}
+
+TEST(FpToStringTest, conversion_float) {
+  // Issue motivating FpToString function,
+  // https://github.com/jbeder/yaml-cpp/issues/1289
+  // Original problem at hand:
+  EXPECT_EQ("34.34", FpToString(34.34f));
+  EXPECT_EQ("56.56", FpToString(56.56f));
+  EXPECT_EQ("12.12", FpToString(12.12f));
+  EXPECT_EQ("78.78", FpToString(78.78f));
+
+  // prints the same way as std::stringstream
+  EXPECT_EQ(convert_with_stringstream(1.f), FpToString(1.f));
+  EXPECT_EQ(convert_with_stringstream(1e0f), FpToString(1e0f));
+  EXPECT_EQ(convert_with_stringstream(1e1f), FpToString(1e1f));
+  EXPECT_EQ(convert_with_stringstream(1e2f), FpToString(1e2f));
+  EXPECT_EQ(convert_with_stringstream(1e3f), FpToString(1e3f));
+  EXPECT_EQ(convert_with_stringstream(1e4f), FpToString(1e4f));
+  EXPECT_EQ(convert_with_stringstream(1e5f), FpToString(1e5f));
+  EXPECT_EQ(convert_with_stringstream(1e6f), FpToString(1e6f));
+  EXPECT_EQ(convert_with_stringstream(1e7f), FpToString(1e7f));
+  EXPECT_EQ(convert_with_stringstream(1e8f), FpToString(1e8f));
+  EXPECT_EQ(convert_with_stringstream(1e9f), FpToString(1e9f));
+
+  // Print by default values below 1e6 without scientific notation
+  EXPECT_EQ("1", FpToString(1.f));
+  EXPECT_EQ("1", FpToString(1e0f));
+  EXPECT_EQ("10", FpToString(1e1f));
+  EXPECT_EQ("100", FpToString(1e2f));
+  EXPECT_EQ("1000", FpToString(1e3f));
+  EXPECT_EQ("10000", FpToString(1e4f));
+  EXPECT_EQ("100000", FpToString(1e5f));
+  EXPECT_EQ("1e+06", FpToString(1e6f));
+  EXPECT_EQ("1e+07", FpToString(1e7f));
+  EXPECT_EQ("1e+08", FpToString(1e8f));
+  EXPECT_EQ("1e+09", FpToString(1e9f));
+
+  // prints the same way as std::stringstream
+  EXPECT_EQ(convert_with_stringstream(1.f), FpToString(1.f));
+  EXPECT_EQ(convert_with_stringstream(1e-0f), FpToString(1e-0f));
+  EXPECT_EQ(convert_with_stringstream(1e-1f), FpToString(1e-1f));
+  EXPECT_EQ(convert_with_stringstream(1e-2f), FpToString(1e-2f));
+  EXPECT_EQ(convert_with_stringstream(1e-3f), FpToString(1e-3f));
+  EXPECT_EQ(convert_with_stringstream(1e-4f), FpToString(1e-4f));
+  EXPECT_EQ(convert_with_stringstream(1e-5f), FpToString(1e-5f));
+  EXPECT_EQ(convert_with_stringstream(1e-6f), FpToString(1e-6f));
+  EXPECT_EQ(convert_with_stringstream(1e-7f), FpToString(1e-7f));
+  EXPECT_EQ(convert_with_stringstream(1e-8f), FpToString(1e-8f));
+  EXPECT_EQ(convert_with_stringstream(1e-9f), FpToString(1e-9f));
+
+  // Print by default values above 1e-5 without scientific notation
+  EXPECT_EQ("1", FpToString(1.f));
+  EXPECT_EQ("1", FpToString(1e-0f));
+  EXPECT_EQ("0.1", FpToString(1e-1f));
+  EXPECT_EQ("0.01", FpToString(1e-2f));
+  EXPECT_EQ("0.001", FpToString(1e-3f));
+  EXPECT_EQ("0.0001", FpToString(1e-4f));
+  EXPECT_EQ("1e-05", FpToString(1e-5f));
+  EXPECT_EQ("1e-06", FpToString(1e-6f));
+  EXPECT_EQ("1e-07", FpToString(1e-7f));
+  EXPECT_EQ("1e-08", FpToString(1e-8f));
+  EXPECT_EQ("1e-09", FpToString(1e-9f));
+
+  // changing precision has the same effect as std::stringstream
+  EXPECT_EQ(convert_with_stringstream(123.f, 1), FpToString(123.f, 1));
+  EXPECT_EQ(convert_with_stringstream(1234567.f, 7), FpToString(1234567.f, 7));
+  EXPECT_EQ(convert_with_stringstream(12345.67f, 7), FpToString(12345.67f, 7));
+  EXPECT_EQ(convert_with_stringstream(1234567e-9f, 7), FpToString(1234567e-9f, 7));
+  EXPECT_EQ(convert_with_stringstream(1234567e-9f, 1), FpToString(1234567e-9f, 1));
+
+ // known example that is difficult to round
+  EXPECT_EQ("1", FpToString(0.9999f, 2));
+  EXPECT_EQ("-1", FpToString(-0.9999f, 2));
+
+  // some more random tests
+  EXPECT_EQ("1.25", FpToString(1.25f));
+  EXPECT_EQ("34.34", FpToString(34.34f));
+  EXPECT_EQ("1e+20", FpToString(1e+20f));
+  EXPECT_EQ("1.1e+20", FpToString(1.1e+20f));
+  EXPECT_EQ("1e-20", FpToString(1e-20f));
+  EXPECT_EQ("1.1e-20", FpToString(1.1e-20f));
+  EXPECT_EQ("1e-20", FpToString(0.1e-19f));
+  EXPECT_EQ("1.1e-20", FpToString(0.11e-19f));
+
+  EXPECT_EQ("19", FpToString(18.9f, 2));
+  EXPECT_EQ("20", FpToString(19.9f, 2));
+  EXPECT_EQ("2e+01", FpToString(19.9f, 1));
+  EXPECT_EQ("1.2e-05", FpToString(1.234e-5f, 2));
+  EXPECT_EQ("1.3e-05", FpToString(1.299e-5f, 2));
+
+  EXPECT_EQ("-1", FpToString(-1.f));
+  EXPECT_EQ("-1.25", FpToString(-1.25f));
+  EXPECT_EQ("-34.34", FpToString(-34.34f));
+  EXPECT_EQ("-1e+20", FpToString(-1e+20f));
+  EXPECT_EQ("-1.1e+20", FpToString(-1.1e+20f));
+  EXPECT_EQ("-1e-20", FpToString(-1e-20f));
+  EXPECT_EQ("-1.1e-20", FpToString(-1.1e-20f));
+  EXPECT_EQ("-1e-20", FpToString(-0.1e-19f));
+  EXPECT_EQ("-1.1e-20", FpToString(-0.11e-19f));
+
+  EXPECT_EQ("-19", FpToString(-18.9f, 2));
+  EXPECT_EQ("-20", FpToString(-19.9f, 2));
+  EXPECT_EQ("-2e+01", FpToString(-19.9f, 1));
+  EXPECT_EQ("-1.2e-05", FpToString(-1.234e-5f, 2));
+  EXPECT_EQ("-1.3e-05", FpToString(-1.299e-5f, 2));
+}
+
+}  // namespace
+}  // namespace YAML

test/integration/emitter_test.cpp

@@ -124,9 +124,11 @@ TEST_F(EmitterTest, NumberPrecision) {
   out << 3.1425926f;
   out << 53.5893;
   out << 2384626.4338;
+  out << 1999926.4338;
+  out << 9999926.4338;
   out << EndSeq;
 
-  ExpectEmit("- 3.14\n- 54\n- 2.4e+06");
+  ExpectEmit("- 3.14\n- 54\n- 2.4e+06\n- 2e+06\n- 1e+07");
 }
 
 TEST_F(EmitterTest, SimpleSeq) {

test/integration/load_node_test.cpp

@@ -224,57 +224,6 @@ TEST(LoadNodeTest, DereferenceIteratorError) {
   EXPECT_THROW(node.begin()->begin()->Type(), InvalidNode);
 }
 
-#ifdef YAML_CPP_SUPPORT_MERGE_KEYS
-TEST(NodeTest, MergeKeyScalarSupport) {
-  Node node = Load("{<<: {a: 1}}");
-  ASSERT_FALSE(!node["a"]);
-  EXPECT_EQ(1, node["a"].as<int>());
-}
-
-TEST(NodeTest, MergeKeyExistingKey) {
-  Node node = Load("{a: 1, <<: {a: 2}}");
-  ASSERT_FALSE(!node["a"]);
-  EXPECT_EQ(1, node["a"].as<int>());
-}
-
-TEST(NodeTest, MergeKeySequenceSupport) {
-  Node node = Load("<<: [{a: 1}, {a: 2, b: 3}]");
-  ASSERT_FALSE(!node["a"]);
-  ASSERT_FALSE(!node["b"]);
-  EXPECT_EQ(1, node["a"].as<int>());
-  EXPECT_EQ(3, node["b"].as<int>());
-}
-
-TEST(NodeTest, NestedMergeKeys) {
-  Node node = Load("{<<: {<<: {a: 1}}}");
-  ASSERT_FALSE(!node["a"]);
-  EXPECT_EQ(1, node["a"].as<int>());
-}
-
-TEST(NodeTest, AnchorAndMergeKey) {
-  Node node = YAML::Load(R"(
-    a_root: &root_anchor
-      key1: value1
-      key2: value2
-    b_child:
-      <<: *root_anchor
-      key2: value2_override
-  )");
-
-  ASSERT_FALSE(!node["a_root"]);
-  ASSERT_FALSE(!node["b_child"]);
-  EXPECT_EQ("value1", node["a_root"]["key1"].as<std::string>());
-  EXPECT_EQ("value2", node["a_root"]["key2"].as<std::string>());
-  EXPECT_EQ("value1", node["b_child"]["key1"].as<std::string>());
-  EXPECT_EQ("value2_override", node["b_child"]["key2"].as<std::string>());
-}
-#else
-TEST(NodeTest, MergeKeySupport) {
-  Node node = Load("{<<: {a: 1}}");
-  ASSERT_FALSE(node["a"]);
-}
-#endif
-
 TEST(NodeTest, EmitEmptyNode) {
   Node node;
   Emitter emitter;

test/node/node_test.cpp

@@ -757,8 +757,15 @@ TEST_F(NodeEmitterTest, SimpleFlowSeqNode) {
   node.push_back(1.5);
   node.push_back(2.25);
   node.push_back(3.125);
+  node.push_back(34.34);
+  node.push_back(56.56);
+  node.push_back(12.12);
+  node.push_back(78.78);
+  node.push_back(0.0003);
+  node.push_back(4000.);
+  node.push_back(1.5474251e+26f);
 
-  ExpectOutput("[1.5, 2.25, 3.125]", node);
+  ExpectOutput("[1.5, 2.25, 3.125, 34.34, 56.56, 12.12, 78.78, 0.0003, 4000, 1.5474251e+26]", node);
 }
 
 TEST_F(NodeEmitterTest, NestFlowSeqNode) {