diff --git a/.github/workflows/real-time-cpp-snippets.yml b/.github/workflows/real-time-cpp-snippets.yml
index e046be3f1..75141ad6a 100644
--- a/.github/workflows/real-time-cpp-snippets.yml
+++ b/.github/workflows/real-time-cpp-snippets.yml
@@ -30,7 +30,7 @@ jobs:
       - name: host-snippets-all
         run: |
           cd ${{ matrix.chapter }}
-          ./${{ matrix.chapter }}.sh ${{ matrix.compiler }} c++20
+          ./${{ matrix.chapter }}.sh ${{ matrix.compiler }} c++23
         working-directory: ./code_snippets
   host-snippets-chapter06:
     runs-on: ubuntu-latest
diff --git a/code_snippets/chapter03/chapter03.sh b/code_snippets/chapter03/chapter03.sh
index 55c8870e3..47fcb013b 100755
--- a/code_snippets/chapter03/chapter03.sh
+++ b/code_snippets/chapter03/chapter03.sh
@@ -70,6 +70,10 @@ ${GCC} -std=${STD} -Wall -Wextra -Wpedantic -Werror -O3 -m64 -fsanitize=address
 ${GCC} -std=${STD} -Wall -Wextra -Wpedantic -Werror -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter03_21-001_span.cpp                     -o ./bin/chapter03_21-001_span.exe
 ${GCC} -std=${STD} -Wall -Wextra -Wpedantic -Werror -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter03_22-001_mersenne_twister_19937.cpp   -o ./bin/chapter03_22-001_mersenne_twister_19937.exe
 ${GCC} -std=${STD} -Wall -Wextra -Wpedantic -Werror -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter03_22-002_test_random_engines.cpp      -o ./bin/chapter03_22-002_test_random_engines.exe
+if [[ "${GCC}" == "g++" ]]; then
+${GCC} -std=${STD} -Wall -Wextra -Wpedantic -Werror -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter03_23-001_expected_div_int.cpp         -o ./bin/chapter03_23-001_expected_div_int.exe
+${GCC} -std=${STD} -Wall -Wextra -Wpedantic -Werror -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter03_23-002_expected_div_integral.cpp    -o ./bin/chapter03_23-002_expected_div_integral.exe
+fi
 
 if [[ "${GCC}" == "g++" ]]; then
 ls -la \
@@ -112,7 +116,9 @@ ls -la \
 ./bin/chapter03_20-002_alias.exe                      \
 ./bin/chapter03_21-001_span.exe                       \
 ./bin/chapter03_22-001_mersenne_twister_19937.exe     \
-./bin/chapter03_22-002_test_random_engines.exe
+./bin/chapter03_22-002_test_random_engines.exe        \
+./bin/chapter03_23-001_expected_div_int.exe           \
+./bin/chapter03_23-002_expected_div_integral.exe
 else
 ls -la \
 ./bin/chapter03_01-001_declare_locals.exe             \
diff --git a/code_snippets/chapter03/chapter03_23-001_expected_div_int.cpp b/code_snippets/chapter03/chapter03_23-001_expected_div_int.cpp
new file mode 100644
index 000000000..5abb1b659
--- /dev/null
+++ b/code_snippets/chapter03/chapter03_23-001_expected_div_int.cpp
@@ -0,0 +1,61 @@
+///////////////////////////////////////////////////////////////////////////////
+//  Copyright Christopher Kormanyos 2025.
+//  Distributed under the Boost Software License,
+//  Version 1.0. (See accompanying file LICENSE_1_0.txt
+//  or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#include <expected>
+#include <iostream>
+
+// chapter03_23-001_expected_div_int.cpp
+
+enum class div_error
+{
+  div_none,
+  div_by_zero
+};
+
+auto safe_divide(int a, int b) noexcept -> std::expected<int, div_error>
+{
+  if (b == 0)
+  {
+    return std::unexpected(div_error::div_by_zero);
+  }
+  else
+  {
+    return a / b;
+  }
+}
+
+auto do_something() -> void
+{
+  // Division by zero.
+  auto result = safe_divide(10, 0);
+
+  if (result.error() == div_error::div_by_zero)
+  {
+    std::cout << "Division by zero" << std::endl;
+  }
+  else
+  {
+    std::cout << "Division ok, result: " << *result << std::endl;
+  }
+
+  result = safe_divide(10, 2);
+
+  if (result.error() == div_error::div_by_zero)
+  {
+    std::cout << "Division by zero" << std::endl;
+  }
+  else
+  {
+    // Division ok, result: 5
+    std::cout << "Division ok, result: " << *result << std::endl;
+  }
+}
+
+auto main() -> int
+{
+  do_something();
+}
diff --git a/code_snippets/chapter03/chapter03_23-002_expected_div_integral.cpp b/code_snippets/chapter03/chapter03_23-002_expected_div_integral.cpp
new file mode 100644
index 000000000..7a3eb58b8
--- /dev/null
+++ b/code_snippets/chapter03/chapter03_23-002_expected_div_integral.cpp
@@ -0,0 +1,64 @@
+///////////////////////////////////////////////////////////////////////////////
+//  Copyright Christopher Kormanyos 2025.
+//  Distributed under the Boost Software License,
+//  Version 1.0. (See accompanying file LICENSE_1_0.txt
+//  or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#include <expected>
+#include <iostream>
+
+// chapter03_23-001_expected_div_int.cpp
+
+enum class div_error
+{
+  div_none,
+  div_by_zero
+};
+
+template<typename T>
+auto safe_divide(T a, T b)
+  -> std::enable_if_t<std::is_integral_v<T>,
+                      std::expected<T, div_error>>
+{
+  if (b == T { 0 })
+  {
+    return std::unexpected(div_error::div_by_zero);
+  }
+  else
+  {
+    return a / b;
+  }
+}
+
+auto do_something() -> void
+{
+  // Division by zero.
+  auto result = safe_divide(10U, 0U);
+
+  if (result.error() == div_error::div_by_zero)
+  {
+    std::cout << "Division by zero" << std::endl;
+  }
+  else
+  {
+    std::cout << "Division ok, result: " << *result << std::endl;
+  }
+
+  result = safe_divide(10, 2);
+
+  if (result.error() == div_error::div_by_zero)
+  {
+    std::cout << "Division by zero" << std::endl;
+  }
+  else
+  {
+    // Division ok, result: 5
+    std::cout << "Division ok, result: " << *result << std::endl;
+  }
+}
+
+auto main() -> int
+{
+  do_something();
+}
diff --git a/code_snippets/chapter05/chapter05.sh b/code_snippets/chapter05/chapter05.sh
index a34c11a1d..895e56af6 100755
--- a/code_snippets/chapter05/chapter05.sh
+++ b/code_snippets/chapter05/chapter05.sh
@@ -36,7 +36,9 @@ $GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion
 $GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_05-002_template_point.cpp                     -o ./bin/chapter05_05-002_template_point.exe
 $GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_05-003_template_point.cpp                     -o ./bin/chapter05_05-003_template_point.exe
 $GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_06-001_template_specialization.cpp            -o ./bin/chapter05_06-001_template_specialization.exe
-$GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_06-002_template_point.cpp                     -o ./bin/chapter05_06-002_template_point.exe
+$GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_06-002_template_enable_if.cpp                 -o ./bin/chapter05_06-002_template_enable_if.exe
+$GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_06-003_template_concepts.cpp                  -o ./bin/chapter05_06-003_template_concepts.exe
+$GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_06-004_template_point.cpp                     -o ./bin/chapter05_06-004_template_point.exe
 $GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_07-001_led_static_polymorphism.cpp            -o ./bin/chapter05_07-001_led_static_polymorphism.exe
 $GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_08-001_using_the_stl.cpp                      -o ./bin/chapter05_08-001_using_the_stl.exe
 $GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_08-002_using_the_stl_algo.cpp                 -o ./bin/chapter05_08-002_using_the_stl_algo.exe
@@ -44,8 +46,8 @@ $GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion
 $GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_09-001_factory_simple.cpp                     -o ./bin/chapter05_09-001_factory_simple.exe
 $GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_09-002_factory_variadic_template.cpp          -o ./bin/chapter05_09-002_factory_variadic_template.exe
 $GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_10-001_metaprogram_factorial.cpp              -o ./bin/chapter05_10-001_metaprogram_factorial.exe
-$GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_10-002_metaprogram_pow10.cpp                  -o ./bin/chapter05_10-002_metaprogram_pow10.exe
-$GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_10-003_metaprogram_inner_product.cpp          -o ./bin/chapter05_10-003_metaprogram_inner_product.exe
+$GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_10-002_const_eval_pow10.cpp                   -o ./bin/chapter05_10-002_const_eval_pow10.exe
+$GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_10-003_const_eval_inner_product.cpp           -o ./bin/chapter05_10-003_const_eval_inner_product.exe
 $GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_11-001_tuple_things_simple.cpp                -o ./bin/chapter05_11-001_tuple_things_simple.exe
 $GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_11-002_tuple_things_metaprogram.cpp           -o ./bin/chapter05_11-002_tuple_things_metaprogram.exe
 $GCC -std=$STD  -Wall -Wextra -Wpedantic -Werror -Wconversion -Wsign-conversion -O3 -m64 -fsanitize=address -fsanitize=shift -fsanitize=shift-exponent -fsanitize=shift-base -fsanitize=integer-divide-by-zero -fsanitize=null -fsanitize=signed-integer-overflow -fsanitize=bounds -fsanitize=alignment -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize=enum ./chapter05_11-003_tuple_things_metaprogram.cpp           -o ./bin/chapter05_11-003_tuple_things_metaprogram.exe
@@ -67,7 +69,9 @@ ls -la \
 ./bin/chapter05_05-002_template_point.exe                  \
 ./bin/chapter05_05-003_template_point.exe                  \
 ./bin/chapter05_06-001_template_specialization.exe         \
-./bin/chapter05_06-002_template_point.exe                  \
+./bin/chapter05_06-002_template_enable_if.exe              \
+./bin/chapter05_06-003_template_concepts.exe               \
+./bin/chapter05_06-004_template_point.exe                  \
 ./bin/chapter05_07-001_led_static_polymorphism.exe         \
 ./bin/chapter05_08-001_using_the_stl.exe                   \
 ./bin/chapter05_08-002_using_the_stl_algo.exe              \
@@ -75,8 +79,8 @@ ls -la \
 ./bin/chapter05_09-001_factory_simple.exe                  \
 ./bin/chapter05_09-002_factory_variadic_template.exe       \
 ./bin/chapter05_10-001_metaprogram_factorial.exe           \
-./bin/chapter05_10-002_metaprogram_pow10.exe               \
-./bin/chapter05_10-003_metaprogram_inner_product.exe       \
+./bin/chapter05_10-002_const_eval_pow10.exe                \
+./bin/chapter05_10-003_const_eval_inner_product.exe        \
 ./bin/chapter05_11-001_tuple_things_simple.exe             \
 ./bin/chapter05_11-002_tuple_things_metaprogram.exe        \
 ./bin/chapter05_11-003_tuple_things_metaprogram.exe        \
diff --git a/code_snippets/chapter05/chapter05_06-001_template_specialization.cpp b/code_snippets/chapter05/chapter05_06-001_template_specialization.cpp
index 849dde956..7af36756c 100644
--- a/code_snippets/chapter05/chapter05_06-001_template_specialization.cpp
+++ b/code_snippets/chapter05/chapter05_06-001_template_specialization.cpp
@@ -1,52 +1,34 @@
 ///////////////////////////////////////////////////////////////////////////////
-//  Copyright Christopher Kormanyos 2017 - 2018.
+//  Copyright Christopher Kormanyos 2017 - 2025.
 //  Distributed under the Boost Software License,
 //  Version 1.0. (See accompanying file LICENSE_1_0.txt
 //  or copy at http://www.boost.org/LICENSE_1_0.txt)
 //
 
 #include <iostream>
+#include <string>
 
 // chapter05_06-001_template_specialization.cpp
 
-// The original add template function.
+// Generic add template function.
 template<typename T>
-T add(const T& a, const T& b)
+auto add(T a, T b) -> T
 {
   return a + b;
 }
 
-// Make template specializations of add() with
-// easy-to-detect errors for float, double
-// and long double.
-
-template<>
-float add<float>(const float&, const float&)
-{
-  // Explicitly create an erroneous result!
-  return 0.0F;
-}
-
+// Specialize add() for the type int.
 template<>
-double add<double>(const double&, const double&)
+auto add<int>(int a, int b) -> int
 {
-  // Explicitly create an erroneous result!
-  return 0.0;
+  return a + b;
 }
 
-template<>
-long double add<long double>(const long double&,
-                             const long double&)
+auto main() -> int
 {
-  // Explicitly create an erroneous result!
-  return 0.0L;
-}
+  // Add with generic template to get result "abcxyz".
+  std::cout << add(std::string("abc"), std::string("xyz")) << std::endl;
 
-int main()
-{
-  // 3
+  // Add with specialized template to get result 3.
   std::cout << add(1, 2) << std::endl;
-
-  // 0
-  std::cout << add(1.0F, 2.0F) << std::endl;
 }
diff --git a/code_snippets/chapter05/chapter05_06-002_template_enable_if.cpp b/code_snippets/chapter05/chapter05_06-002_template_enable_if.cpp
new file mode 100644
index 000000000..cc750fcb3
--- /dev/null
+++ b/code_snippets/chapter05/chapter05_06-002_template_enable_if.cpp
@@ -0,0 +1,40 @@
+///////////////////////////////////////////////////////////////////////////////
+//  Copyright Christopher Kormanyos 2017 - 2025.
+//  Distributed under the Boost Software License,
+//  Version 1.0. (See accompanying file LICENSE_1_0.txt
+//  or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#include <iostream>
+
+// chapter05_06-002_template_enable_if.cpp
+
+// The original add template function.
+template<typename T>
+auto add(T a, T b) noexcept
+  -> std::enable_if_t<!std::is_floating_point_v<T>, T>
+{
+  return a + b;
+}
+
+// Easy-to-detect errors for float, double
+// and long double.
+
+template<typename T>
+auto add(T, T) noexcept
+  -> std::enable_if_t<std::is_floating_point_v<T>, T>
+{
+  // Explicitly create an erroneous result!
+  return T { 0.0F };
+}
+
+auto main() -> int;
+
+auto main() -> int
+{
+  // 3
+  std::cout << add(1, 2) << std::endl;
+
+  // 0
+  std::cout << add(1.0F, 2.0F) << std::endl;
+}
diff --git a/code_snippets/chapter05/chapter05_06-003_template_concepts.cpp b/code_snippets/chapter05/chapter05_06-003_template_concepts.cpp
new file mode 100644
index 000000000..238047168
--- /dev/null
+++ b/code_snippets/chapter05/chapter05_06-003_template_concepts.cpp
@@ -0,0 +1,46 @@
+///////////////////////////////////////////////////////////////////////////////
+//  Copyright Christopher Kormanyos 2025.
+//  Distributed under the Boost Software License,
+//  Version 1.0. (See accompanying file LICENSE_1_0.txt
+//  or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#include <concepts>
+#include <iostream>
+#include <string>
+#include <type_traits>
+
+// chapter05_06-003_template_concepts.cpp
+
+// Generic add template function.
+template<typename T>
+auto add(T a, T b) -> T
+{
+  return a + b;
+}
+
+template<typename T>
+requires std::integral<T>
+auto add(T a, T b) -> T
+{
+  return a + b;
+}
+
+auto do_something() -> void
+{
+  // 3U
+  const unsigned c { add(1U, 2U) };
+
+  std::cout << c << std::endl;
+
+  // abcxyz
+  const std::string str
+    { add(std::string("abc"), std::string("xyz")) };
+
+  std::cout << str << std::endl;
+}
+
+auto main() -> int
+{
+  do_something();
+}
diff --git a/code_snippets/chapter05/chapter05_06-002_template_point.cpp b/code_snippets/chapter05/chapter05_06-004_template_point.cpp
similarity index 93%
rename from code_snippets/chapter05/chapter05_06-002_template_point.cpp
rename to code_snippets/chapter05/chapter05_06-004_template_point.cpp
index 80a5e347f..6ddeb2a03 100644
--- a/code_snippets/chapter05/chapter05_06-002_template_point.cpp
+++ b/code_snippets/chapter05/chapter05_06-004_template_point.cpp
@@ -1,11 +1,11 @@
 ///////////////////////////////////////////////////////////////////////////////
-//  Copyright Christopher Kormanyos 2017 - 2023.
+//  Copyright Christopher Kormanyos 2017 - 2025.
 //  Distributed under the Boost Software License,
 //  Version 1.0. (See accompanying file LICENSE_1_0.txt
 //  or copy at http://www.boost.org/LICENSE_1_0.txt)
 //
 
-// chapter05_06-002_template_point.cpp
+// chapter05_06-004_template_point.cpp
 
 #include <cstdint>
 #include <iostream>
diff --git a/code_snippets/chapter05/chapter05_10-002_const_eval_pow10.cpp b/code_snippets/chapter05/chapter05_10-002_const_eval_pow10.cpp
new file mode 100644
index 000000000..c58ab3039
--- /dev/null
+++ b/code_snippets/chapter05/chapter05_10-002_const_eval_pow10.cpp
@@ -0,0 +1,58 @@
+///////////////////////////////////////////////////////////////////////////////
+//  Copyright Christopher Kormanyos 2018 - 2025.
+//  Distributed under the Boost Software License,
+//  Version 1.0. (See accompanying file LICENSE_1_0.txt
+//  or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+// chapter05_10-002_const_eval_pow10.cpp
+
+#include <cstdint>
+#include <cmath>
+#include <iostream>
+#include <type_traits>
+
+extern std::uint32_t p_nonconst;
+
+template<typename T>
+constexpr auto pow10(T p)
+  -> std::enable_if_t<std::is_unsigned_v<T>, T>;
+
+template<typename T>
+constexpr auto pow10(T p)
+  -> std::enable_if_t<std::is_unsigned_v<T>, T>
+{
+  if(std::is_constant_evaluated())
+  {
+    constexpr T ten { 10 };
+
+    return   p == 0 ? T { 1 }
+           : p == 1 ? ten
+           : ten * pow10(T { p - 1U });
+  }
+  else
+  {
+    using std::pow;
+
+    return static_cast<T>(pow(10, p));
+  }
+}
+
+auto main() -> int
+{
+  constexpr std::uint32_t p { UINT64_C(6) };
+
+  // This is constexpr.
+  constexpr std::uint32_t million { pow10(p) };
+
+  static_assert(million == UINT32_C(1'000'000),
+                "Error: wrong result for pow10 function.");
+
+  // This is not constexpr.
+  const std::uint32_t million_nonconst { pow10(p_nonconst) };
+
+  std::cout << "million:          " << million          << std::endl;
+  std::cout << "million_nonconst: " << million_nonconst << std::endl;
+}
+
+std::uint32_t p_nonconst { UINT64_C(6) };
diff --git a/code_snippets/chapter05/chapter05_10-002_metaprogram_pow10.cpp b/code_snippets/chapter05/chapter05_10-002_metaprogram_pow10.cpp
deleted file mode 100644
index 1cff2dee0..000000000
--- a/code_snippets/chapter05/chapter05_10-002_metaprogram_pow10.cpp
+++ /dev/null
@@ -1,33 +0,0 @@
-///////////////////////////////////////////////////////////////////////////////
-//  Copyright Christopher Kormanyos 2018 - 2019.
-//  Distributed under the Boost Software License,
-//  Version 1.0. (See accompanying file LICENSE_1_0.txt
-//  or copy at http://www.boost.org/LICENSE_1_0.txt)
-//
-
-// chapter05_10-002_metaprogram_pow10.cpp
-
-#include <cstdint>
-#include <iostream>
-
-template<const std::uint32_t n>
-constexpr std::uint32_t pow10()
-{
-  static_assert(n <= 9U, "Error: n is limited to 9 or less.");
-
-  return pow10<n - 1U>() * UINT32_C(10);
-};
-
-template<>
-constexpr std::uint32_t pow10<UINT32_C(0)>()
-{
-  return UINT32_C(1);
-};
-
-int main()
-{
-  // 1,000,000
-  constexpr std::uint32_t million = pow10<6U>();
-
-  std::cout << million << std::endl;
-}
diff --git a/code_snippets/chapter05/chapter05_10-003_const_eval_inner_product.cpp b/code_snippets/chapter05/chapter05_10-003_const_eval_inner_product.cpp
new file mode 100644
index 000000000..422a7b645
--- /dev/null
+++ b/code_snippets/chapter05/chapter05_10-003_const_eval_inner_product.cpp
@@ -0,0 +1,40 @@
+///////////////////////////////////////////////////////////////////////////////
+//  Copyright Christopher Kormanyos 2018 - 2025.
+//  Distributed under the Boost Software License,
+//  Version 1.0. (See accompanying file LICENSE_1_0.txt
+//  or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+// chapter05_10-003_const_eval_inner_product.cpp
+
+#include <array>
+#include <iostream>
+#include <numeric>
+
+// chapter05_10-003_const_eval_inner_product.cpp
+
+constexpr std::array<unsigned, 3U> u
+{
+  { 1U, 2U, 3U }
+};
+
+constexpr std::array<unsigned, 3U> v
+{
+  { 4U, 5U, 6U }
+};
+
+// The result is 32.
+constexpr unsigned w
+{
+  std::inner_product(u.cbegin(),
+                     u.cend(),
+                     v.cbegin(),
+                     0U)
+};
+
+static_assert(w == 32U, "Error in inner_produce");
+
+auto main() -> int
+{
+  std::cout << "Result of inner product is: " << w << std::endl;
+}
diff --git a/code_snippets/chapter05/chapter05_10-003_metaprogram_inner_product.cpp b/code_snippets/chapter05/chapter05_10-003_metaprogram_inner_product.cpp
deleted file mode 100644
index 7a17cdb18..000000000
--- a/code_snippets/chapter05/chapter05_10-003_metaprogram_inner_product.cpp
+++ /dev/null
@@ -1,69 +0,0 @@
-///////////////////////////////////////////////////////////////////////////////
-//  Copyright Christopher Kormanyos 2018.
-//  Distributed under the Boost Software License,
-//  Version 1.0. (See accompanying file LICENSE_1_0.txt
-//  or copy at http://www.boost.org/LICENSE_1_0.txt)
-//
-
-// chapter05_10-003_metaprogram_inner_product.cpp
-
-#include <array>
-#include <cstddef>
-#include <cstdint>
-#include <iostream>
-
-template<const std::size_t N,
-         const std::size_t M = 0U>
-struct inner_product
-{
-  template<typename iterator_left,
-           typename iterator_right,
-           typename result_type>
-  static result_type sum(iterator_left u,
-                         iterator_right v,
-                         const result_type& init)
-  {
-    // Add (u[M] * v[M]) recursively.
-    const result_type uvm
-      = *(u + M) * result_type(*(v + M));
-
-    return uvm
-      + inner_product<N, M + 1U>::sum(u, v, init);
-  }
-};
-
-template<const std::size_t N>
-struct inner_product<N, N>
-{
-  template<typename iterator_left,
-           typename iterator_right,
-           typename result_type>
-  static result_type sum(iterator_left,
-                         iterator_right,
-                         const result_type&)
-  {
-    // N'th specialization terminates the recursion.
-    return result_type(0);
-  }
-};
-
-int main()
-{
-  constexpr std::array<unsigned, 3U> u
-  {
-    { 1U, 2U, 3U }
-  };
-
-  constexpr std::array<unsigned, 3U> v
-  {
-    { 4U, 5U, 6U }
-  };
-
-  // The result is 32.
-  const unsigned w =
-    inner_product<3U>::sum(u.cbegin(),
-                           v.cbegin(),
-                           0U);
-
-  std::cout << "Result of inner product is: " << w << std::endl;
-}
diff --git a/examples/chapter02_02/chapter02_02.vcxproj b/examples/chapter02_02/chapter02_02.vcxproj
index 40036ff57..a773fe7b4 100644
--- a/examples/chapter02_02/chapter02_02.vcxproj
+++ b/examples/chapter02_02/chapter02_02.vcxproj
@@ -45,10 +45,10 @@
   </ImportGroup>
   <PropertyGroup Label="UserMacros" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='avr|Win32'">
-    <NMakeBuildCommandLine>build.bat $(SolutionDir)tools\Util\msys64\usr\local\gcc-11.2.0-avr\bin avr</NMakeBuildCommandLine>
+    <NMakeBuildCommandLine>build.bat $(SolutionDir)tools\Util\msys64\usr\local\gcc-15.1.0-avr\bin avr</NMakeBuildCommandLine>
     <NMakeOutput>$(OutDir)led.hex</NMakeOutput>
     <NMakeCleanCommandLine>del /Q bin\*.*</NMakeCleanCommandLine>
-    <NMakeReBuildCommandLine>build.bat $(SolutionDir)tools\Util\msys64\usr\local\gcc-11.2.0-avr\bin avr</NMakeReBuildCommandLine>
+    <NMakeReBuildCommandLine>build.bat $(SolutionDir)tools\Util\msys64\usr\local\gcc-15.1.0-avr\bin avr</NMakeReBuildCommandLine>
     <NMakePreprocessorDefinitions>
     </NMakePreprocessorDefinitions>
     <IntDir>$(SolutionDir)bin\</IntDir>
@@ -65,6 +65,9 @@
     <BuildLog>
       <Path>$(OutDir)$(Configuration).log</Path>
     </BuildLog>
+    <ClCompile>
+      <LanguageStandard>stdcpp20</LanguageStandard>
+    </ClCompile>
   </ItemDefinitionGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
diff --git a/examples/chapter02_02/mcal_reg.h b/examples/chapter02_02/mcal_reg.h
index 7148876e1..a8eef6cb6 100644
--- a/examples/chapter02_02/mcal_reg.h
+++ b/examples/chapter02_02/mcal_reg.h
@@ -10,21 +10,19 @@
 
   #include <cstdint>
 
-  namespace mcal
-  {
-    namespace reg
-    {
-      constexpr std::uint8_t portb { UINT8_C(0x25U) };
+  namespace mcal::reg {
 
-      constexpr std::uint8_t bval0 { UINT8_C(0x01) };
-      constexpr std::uint8_t bval1 { UINT8_C(0x01) << 1U };
-      constexpr std::uint8_t bval2 { UINT8_C(0x01) << 2U };
-      constexpr std::uint8_t bval3 { UINT8_C(0x01) << 3U };
-      constexpr std::uint8_t bval4 { UINT8_C(0x01) << 4U };
-      constexpr std::uint8_t bval5 { UINT8_C(0x01) << 5U };
-      constexpr std::uint8_t bval6 { UINT8_C(0x01) << 6U };
-      constexpr std::uint8_t bval7 { UINT8_C(0x01) << 7U };
-    }
-  }
+  constexpr std::uint8_t portb { UINT8_C(0x25U) };
+
+  constexpr std::uint8_t bval0 { UINT8_C(0x01) };
+  constexpr std::uint8_t bval1 { UINT8_C(0x01) << 1U };
+  constexpr std::uint8_t bval2 { UINT8_C(0x01) << 2U };
+  constexpr std::uint8_t bval3 { UINT8_C(0x01) << 3U };
+  constexpr std::uint8_t bval4 { UINT8_C(0x01) << 4U };
+  constexpr std::uint8_t bval5 { UINT8_C(0x01) << 5U };
+  constexpr std::uint8_t bval6 { UINT8_C(0x01) << 6U };
+  constexpr std::uint8_t bval7 { UINT8_C(0x01) << 7U };
+
+  } // namespace mcal::reg
 
 #endif // MCAL_REG_2011_11_04_H
diff --git a/examples/chapter02_06/chapter02_06.vcxproj b/examples/chapter02_06/chapter02_06.vcxproj
index 8d86bb5eb..a773fe7b4 100644
--- a/examples/chapter02_06/chapter02_06.vcxproj
+++ b/examples/chapter02_06/chapter02_06.vcxproj
@@ -65,6 +65,9 @@
     <BuildLog>
       <Path>$(OutDir)$(Configuration).log</Path>
     </BuildLog>
+    <ClCompile>
+      <LanguageStandard>stdcpp20</LanguageStandard>
+    </ClCompile>
   </ItemDefinitionGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
diff --git a/examples/chapter02_06/mcal_reg.h b/examples/chapter02_06/mcal_reg.h
index 7148876e1..a8eef6cb6 100644
--- a/examples/chapter02_06/mcal_reg.h
+++ b/examples/chapter02_06/mcal_reg.h
@@ -10,21 +10,19 @@
 
   #include <cstdint>
 
-  namespace mcal
-  {
-    namespace reg
-    {
-      constexpr std::uint8_t portb { UINT8_C(0x25U) };
+  namespace mcal::reg {
 
-      constexpr std::uint8_t bval0 { UINT8_C(0x01) };
-      constexpr std::uint8_t bval1 { UINT8_C(0x01) << 1U };
-      constexpr std::uint8_t bval2 { UINT8_C(0x01) << 2U };
-      constexpr std::uint8_t bval3 { UINT8_C(0x01) << 3U };
-      constexpr std::uint8_t bval4 { UINT8_C(0x01) << 4U };
-      constexpr std::uint8_t bval5 { UINT8_C(0x01) << 5U };
-      constexpr std::uint8_t bval6 { UINT8_C(0x01) << 6U };
-      constexpr std::uint8_t bval7 { UINT8_C(0x01) << 7U };
-    }
-  }
+  constexpr std::uint8_t portb { UINT8_C(0x25U) };
+
+  constexpr std::uint8_t bval0 { UINT8_C(0x01) };
+  constexpr std::uint8_t bval1 { UINT8_C(0x01) << 1U };
+  constexpr std::uint8_t bval2 { UINT8_C(0x01) << 2U };
+  constexpr std::uint8_t bval3 { UINT8_C(0x01) << 3U };
+  constexpr std::uint8_t bval4 { UINT8_C(0x01) << 4U };
+  constexpr std::uint8_t bval5 { UINT8_C(0x01) << 5U };
+  constexpr std::uint8_t bval6 { UINT8_C(0x01) << 6U };
+  constexpr std::uint8_t bval7 { UINT8_C(0x01) << 7U };
+
+  } // namespace mcal::reg
 
 #endif // MCAL_REG_2011_11_04_H