Update format docs and examples

doc/modules/ROOT/pages/format.adoc

@@ -8,7 +8,7 @@ https://www.boost.org/LICENSE_1_0.txt
 = Formating support
 :idprefix: format_
 
-Boost.Decimal supports formatting with both `<format>` (when C++20 and header are both available) and `<fmt/format.h>`.
+Boost.Decimal supports formatting with both `<format>` (when C++20 and header are both available), and `<fmt/format.h>` with all language standards.
 
 [#std_format]
 == `<format>`
@@ -87,31 +87,8 @@ String literal pass:["{Sign, Padding, Precision, Type, Locale}"]
 
 === Examples
 
-The example is padding modifiers can be done like so
+This example can be found in the examples/ folder as https://github.com/cppalliance/decimal/blob/develop/examples/fmt_format.cpp[fmt_format.cpp]
 
-[source, c++]
-----
-#include <boost/decimal.hpp> // or <boost/decimal/format.hpp>
-#include <format>
-#include <iostream>
-
-int main()
-{
-    constexpr boost::decimal::decimal64_t val1 {314, -2};
-    constexpr boost::decimal::decimal32_t val2 {3141, -3};
-
-    std::cout << std::format("{:10.3e}", val1) << '\n';
-    std::cout << std::format("{:10.3e}", val2) << std::endl;
-
-    return 0;
-}
-----
-
-[#fmt_format]
-== `<fmt/format.h>`
-
-Support for pass:[{fmt}] is also available.
-All the above information on modifiers is the same for fmtlib, just in a different namespace (i.e. `fmt::` instead of `std::`).
 The header `<boost/decimal/fmt_format.hpp>` is *NOT* part of the convenience header, because it is an optional dependency on a potentially compiled library.
 
 [source, c++]
@@ -123,12 +100,52 @@ The header `<boost/decimal/fmt_format.hpp>` is *NOT* part of the convenience hea
 
 int main()
 {
-    constexpr boost::decimal::decimal64_t val1 {314, -2};
-    constexpr boost::decimal::decimal32_t val2 {3141, -3};
-
+    constexpr boost::decimal::decimal64_t val1 {"3.14"};
+    constexpr boost::decimal::decimal32_t val2 {"3.141"};
+
+    // The easiest is no specification which is general format
+    // Given these values they will print in fixed format
+    std::cout << "Default Format:\n";
+    std::cout << fmt::format("{}", val1) << '\n';
+    std::cout << fmt::format("{}", val2) << "\n\n";
+
+    // Next we can add a type modifier to get scientific formatting
+    std::cout << "Scientific Format:\n";
+    std::cout << fmt::format("{:e}", val1) << '\n';
+    std::cout << fmt::format("{:e}", val2) << "\n\n";
+
+    // Next we can add a type modifier to get scientific formatting
+    // Here this gives one digit of precision rounded according to current rounding mode
+    std::cout << "Scientific Format with Specified Precision:\n";
+    std::cout << fmt::format("{:.1e}", val1) << '\n';
+    std::cout << fmt::format("{:.1e}", val2) << "\n\n";
+
+    // This combines the padding modifier (10), precision (3 digits), and a type modifier (e)
+    std::cout << "Scientific Format with Specified Precision and Padding:\n";
     std::cout << fmt::format("{:10.3e}", val1) << '\n';
-    std::cout << fmt::format("{:10.3e}", val2) << std::endl;
+    std::cout << fmt::format("{:10.3e}", val2) << '\n';
 
     return 0;
 }
 ----
+
+Output:
+----
+Default Format:
+3.14
+3.141
+
+Scientific Format:
+3.14e+00
+3.141e+00
+
+Scientific Format with Specified Precision:
+3.1e+00
+3.1e+00
+
+Scientific Format with Specified Precision and Padding:
+03.140e+00
+03.141e+00
+----
+
+This same example can be run with `<format>` by replacing namespaces `fmt::` with `std::`.

examples/fmt_format.cpp

@@ -10,8 +10,8 @@
 
 int main()
 {
-    constexpr boost::decimal::decimal64_t val1 {314, -2};
-    constexpr boost::decimal::decimal32_t val2 {3141, -3};
+    constexpr boost::decimal::decimal64_t val1 {"3.14"};
+    constexpr boost::decimal::decimal32_t val2 {"3.141"};
 
     // The easiest is no specification which is general format
     // Given these values they will print in fixed format

examples/format.cpp

@@ -11,11 +11,30 @@
 
 int main()
 {
-    constexpr boost::decimal::decimal64_t val1 {314, -2};
-    constexpr boost::decimal::decimal32_t val2 {3141, -3};
-
+    constexpr boost::decimal::decimal64_t val1 {"3.14"};
+    constexpr boost::decimal::decimal32_t val2 {"3.141"};
+
+    // The easiest is no specification which is general format
+    // Given these values they will print in fixed format
+    std::cout << "Default Format:\n";
+    std::cout << std::format("{}", val1) << '\n';
+    std::cout << std::format("{}", val2) << "\n\n";
+
+    // Next we can add a type modifier to get scientific formatting
+    std::cout << "Scientific Format:\n";
+    std::cout << std::format("{:e}", val1) << '\n';
+    std::cout << std::format("{:e}", val2) << "\n\n";
+
+    // Next we can add a type modifier to get scientific formatting
+    // Here this gives one digit of precision rounded according to current rounding mode
+    std::cout << "Scientific Format with Specified Precision:\n";
+    std::cout << std::format("{:.1e}", val1) << '\n';
+    std::cout << std::format("{:.1e}", val2) << "\n\n";
+
+    // This combines the padding modifier (10), precision (3 digits), and a type modifier (e)
+    std::cout << "Scientific Format with Specified Precision and Padding:\n";
     std::cout << std::format("{:10.3e}", val1) << '\n';
-    std::cout << std::format("{:10.3e}", val2) << std::endl;
+    std::cout << std::format("{:10.3e}", val2) << '\n';
 
     return 0;
 }

include/boost/decimal/format.hpp

@@ -5,9 +5,7 @@
 #ifndef BOOST_DECIMAL_FORMAT_HPP
 #define BOOST_DECIMAL_FORMAT_HPP
 
-// Many compilers seem to have <format> with completely broken support so narrow down our support range
-#if (__cplusplus >= 202002L || (defined(_MSVC_LANG) && _MSVC_LANG >= 202002L)) && !defined(BOOST_DECIMAL_DISABLE_CLIB) && \
-    ((defined(__GNUC__) && __GNUC__ >= 13) || (defined(__clang__) && __clang_major__ >= 18) || (defined(_MSC_VER) && _MSC_VER >= 1940))
+#if __has_include(<format>) && defined(__cpp_lib_format) && __cpp_lib_format >= 201907L && !defined(BOOST_DECIMAL_DISABLE_CLIB)
 
 #define BOOST_DECIMAL_HAS_FORMAT_SUPPORT
 
@@ -315,6 +313,6 @@ struct formatter<T, CharT>
 
 } // Namespace std
 
-#endif
+#endif // <format> compatibility
 
 #endif //BOOST_DECIMAL_FORMAT_HPP