diff --git a/include/boost/fixed_string/config.hpp b/include/boost/fixed_string/config.hpp
index 4323c22..b7cae89 100644
--- a/include/boost/fixed_string/config.hpp
+++ b/include/boost/fixed_string/config.hpp
@@ -10,8 +10,10 @@
 #ifndef BOOST_FIXED_STRING_CONFIG_HPP
 #define BOOST_FIXED_STRING_CONFIG_HPP
 
-#define BOOST_FIXED_STRING_USE_BOOST
+// Are we dependent on Boost?
+//#define BOOST_FIXED_STRING_USE_BOOST
 
+// C++ version
 #if __cplusplus >= 201703L
 #define BOOST_FIXED_STRING_CPP17
 #elif __cplusplus >= 201402L
@@ -20,16 +22,43 @@
 #define BOOST_FIXED_STRING_CPP11
 #endif
 
+// See if we can use `string_view`
 #if defined(BOOST_FIXED_STRING_CPP17) || defined(BOOST_FIXED_STRING_USE_BOOST)
 #define BOOST_FIXED_STRING_STRING_VIEW
 #endif
 
 #ifdef BOOST_FIXED_STRING_USE_BOOST
 #include <boost/utility/string_view.hpp>
-#elif defined(BOOST_FIXED_STRING_CPP17)
+#include <boost/assert.hpp>
+#include <boost/static_assert.hpp>
+#include <boost/throw_exception.hpp>
+#else
+#include <cassert>
+#ifdef BOOST_FIXED_STRING_CPP17
 #include <string_view>
 #endif
+#endif
 
+// Boost and non-Boost versions of utilities
+#ifdef BOOST_FIXED_STRING_USE_BOOST
+#define BOOST_FIXED_STRING_THROW(ex) BOOST_THROW_EXCEPTION(ex)
+#define BOOST_FIXED_STRING_STATIC_ASSERT(cond, msg) BOOST_STATIC_ASSERT_MSG(cond, msg)
+#define BOOST_FIXED_STRING_ASSERT(cond) BOOST_ASSERT(cond)
+#ifdef BOOST_NODISCARD
+#define BOOST_FIXED_STRING_NODISCARD BOOST_NODISCARD
+#else
+#define BOOST_FIXED_STRING_NODISCARD
+#endif
+#else
+#define BOOST_FIXED_STRING_THROW(ex) throw ex
+#define BOOST_FIXED_STRING_STATIC_ASSERT(cond, msg) static_assert(cond, msg)
+#define BOOST_FIXED_STRING_ASSERT(cond) assert(cond)
+#ifdef BOOST_FIXED_STRING_CPP17
+#define BOOST_FIXED_STRING_NODISCARD [[nodiscard]]
+#else
+#define BOOST_FIXED_STRING_NODISCARD
+#endif
+#endif
 
 namespace boost {
 namespace fixed_string {
@@ -54,17 +83,6 @@ using basic_string_view =
     std::basic_string_view<CharT, Traits>;
 #endif
 #endif
-
-#ifndef BOOST_NODISCARD
-#define BOOST_NODISCARD
-#endif
-
-#ifdef BOOST_FIXED_STRING_USE_BOOST
-#define BOOST_FIXED_STRING_THROW(e) (BOOST_THROW_EXCEPTION(e))
-#else
-#define BOOST_FIXED_STRING_THROW(e) (throw e)
-#endif
-
 } // fixed_string
 } // boost
 
diff --git a/include/boost/fixed_string/detail/fixed_string.hpp b/include/boost/fixed_string/detail/fixed_string.hpp
index 3a0542e..d1d3df4 100644
--- a/include/boost/fixed_string/detail/fixed_string.hpp
+++ b/include/boost/fixed_string/detail/fixed_string.hpp
@@ -10,7 +10,7 @@
 #ifndef BOOST_FIXED_STRING_DETAIL_FIXED_STRING_HPP
 #define BOOST_FIXED_STRING_DETAIL_FIXED_STRING_HPP
 
-#include <boost/assert.hpp>
+#include <boost/fixed_string/config.hpp>
 #include <boost/core/ignore_unused.hpp>
 #include <iterator>
 #include <type_traits>
@@ -126,11 +126,7 @@ CharT*
 raw_to_string(CharT* last, std::size_t size, Integer i)
 {
     boost::ignore_unused(size);
-#ifdef BOOST_FIXED_STRING_USE_BOOST
-    BOOST_ASSERT(size >= max_digits(sizeof(Integer)));
-#else
-    assert(size >= max_digits(sizeof(Integer)));
-#endif
+    BOOST_FIXED_STRING_ASSERT(size >= max_digits(sizeof(Integer)));
     return raw_to_string<CharT, Integer, Traits>(
         last, i, std::is_signed<Integer>{});
 }
diff --git a/include/boost/fixed_string/fixed_string.hpp b/include/boost/fixed_string/fixed_string.hpp
index fb3e988..c79046d 100644
--- a/include/boost/fixed_string/fixed_string.hpp
+++ b/include/boost/fixed_string/fixed_string.hpp
@@ -607,7 +607,7 @@ public:
     //--------------------------------------------------------------------------
 
     /// Returns `true` if the string is empty.
-    BOOST_NODISCARD
+    BOOST_FIXED_STRING_NODISCARD
     bool
     empty() const
     {
@@ -916,12 +916,8 @@ public:
     void
     pop_back()
     {
-#ifdef BOOST_FIXED_STRING_USE_BOOST
-        BOOST_ASSERT(n_ > 0);
-#else
-        assert(n > 0);
-#endif
-        Traits::assign(s_[--n_], 0);
+      BOOST_FIXED_STRING_ASSERT(n_ > 0);
+      Traits::assign(s_[--n_], 0);
     }
 
     /** Appends `count` copies of character `ch`
@@ -1326,16 +1322,17 @@ public:
     swap(
         fixed_string<M, CharT, Traits>& s);
 
-
+    template<size_t N>
     fixed_string&
     replace(
         size_type pos1,
         size_type n1,
-        const fixed_string& str)
+        const fixed_string<N, CharT, Traits>& str)
     {
       return replace(pos1, n1, str.data(), str.size());
     }
 
+    
     fixed_string&
     replace(
         size_type pos1,
@@ -1344,7 +1341,7 @@ public:
         size_type pos2,
         size_type n2 = npos)
     {
-      return replace(pos1, n1, string_view_type(str).substr(pos2, n2));
+      return replace(pos1, n1, str.substr(pos2, n2));
     }
 
 #ifdef BOOST_FIXED_STRING_STRING_VIEW
@@ -1369,7 +1366,8 @@ public:
 
 #ifdef BOOST_FIXED_STRING_STRING_VIEW
     template<typename T>
-#if GENERATING_DOCUMENTATION
+#if GENERATI
+    NG_DOCUMENTATION
     fixed_string&
 #else
     typename std::enable_if<
diff --git a/include/boost/fixed_string/impl/fixed_string.hpp b/include/boost/fixed_string/impl/fixed_string.hpp
index 15c7862..7168476 100644
--- a/include/boost/fixed_string/impl/fixed_string.hpp
+++ b/include/boost/fixed_string/impl/fixed_string.hpp
@@ -12,9 +12,6 @@
 
 #include <boost/fixed_string/config.hpp>
 #include <boost/fixed_string/detail/fixed_string.hpp>
-#include <boost/assert.hpp>
-#include <boost/static_assert.hpp>
-#include <boost/throw_exception.hpp>
 
 namespace boost {
 namespace fixed_string {
@@ -795,11 +792,7 @@ to_fixed_string(Integer x)
 {
     using CharT = char;
     using Traits = std::char_traits<CharT>;
-#ifdef BOOST_FIXED_STRING_USE_BOOST
-    BOOST_STATIC_ASSERT(std::is_integral<Integer>::value);
-#else
-    static_assert(std::is_integral<Integer>::value);
-#endif
+    BOOST_FIXED_STRING_STATIC_ASSERT(std::is_integral<Integer>::value, "Integer must be an integral type");
     char buf[detail::max_digits(sizeof(Integer))];
     auto last = buf + sizeof(buf);
     auto it = detail::raw_to_string<