Fix clang-tidy findings and document JSON_USE_SIMDUTF in the nav

- number_parse.hpp: use std::array for the powers-of-ten table
  (avoid-c-arrays) and `auto` for the cast-initialized result
  (modernize-use-auto), matching the codebase style (cf. the serializer's
  utf8d table). Indexing casts keep the -Wsign-conversion build clean.
- add JSON_USE_SIMDUTF to the mkdocs navigation so the macro page is
  reachable.

No behavior change; clang-tidy is clean on the new headers and the
amalgamation is regenerated.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AXcDtEma2PjxgmPS9cQGzA
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

docs/mkdocs/mkdocs.yml

@@ -296,6 +296,7 @@ nav:
           - 'JSON_USE_GLOBAL_UDLS': api/macros/json_use_global_udls.md
           - 'JSON_USE_IMPLICIT_CONVERSIONS': api/macros/json_use_implicit_conversions.md
           - 'JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON': api/macros/json_use_legacy_discarded_value_comparison.md
+          - 'JSON_USE_SIMDUTF': api/macros/json_use_simdutf.md
           - 'NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE': api/macros/nlohmann_define_derived_type.md
           - 'NLOHMANN_DEFINE_TYPE_INTRUSIVE, NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE': api/macros/nlohmann_define_type_intrusive.md
           - 'NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE': api/macros/nlohmann_define_type_non_intrusive.md

include/nlohmann/detail/input/number_parse.hpp

@@ -8,6 +8,8 @@
 
 #pragma once
 
+#include <array> // array
+#include <cstddef> // size_t
 #include <cstdint> // int64_t, uint64_t
 #include <limits> // numeric_limits
 
@@ -113,10 +115,12 @@ below).
 template<typename DecimalPointType>
 bool parse_float_fast(const char* first, const char* last, DecimalPointType decimal_point, double& out) noexcept
 {
-    static const double powers_of_ten[] =
+    static const std::array<double, 23> powers_of_ten =
     {
-        1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9, 1e10, 1e11,
+        {
-        1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19, 1e20, 1e21, 1e22
+            1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9, 1e10, 1e11,
+            1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19, 1e20, 1e21, 1e22
+        }
     };
 
     const char* p = first;
@@ -208,14 +212,14 @@ bool parse_float_fast(const char* first, const char* last, DecimalPointType deci
         return false; // significand not exactly representable as double
     }
 
-    double result = static_cast<double>(significand);
+    auto result = static_cast<double>(significand);
     if (scale >= 0)
     {
         if (JSON_HEDLEY_UNLIKELY(scale > 22))
         {
             return false;
         }
-        result *= powers_of_ten[scale];
+        result *= powers_of_ten[static_cast<std::size_t>(scale)];
     }
     else
     {
@@ -223,7 +227,7 @@ bool parse_float_fast(const char* first, const char* last, DecimalPointType deci
         {
             return false;
         }
-        result /= powers_of_ten[-scale];
+        result /= powers_of_ten[static_cast<std::size_t>(-scale)];
     }
     out = negative ? -result : result;
     return true;

single_include/nlohmann/json.hpp

@@ -7790,6 +7790,8 @@ NLOHMANN_JSON_NAMESPACE_END
 
 
 
+#include <array> // array
+#include <cstddef> // size_t
 #include <cstdint> // int64_t, uint64_t
 #include <limits> // numeric_limits
 
@@ -7896,10 +7898,12 @@ below).
 template<typename DecimalPointType>
 bool parse_float_fast(const char* first, const char* last, DecimalPointType decimal_point, double& out) noexcept
 {
-    static const double powers_of_ten[] =
+    static const std::array<double, 23> powers_of_ten =
     {
-        1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9, 1e10, 1e11,
+        {
-        1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19, 1e20, 1e21, 1e22
+            1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9, 1e10, 1e11,
+            1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19, 1e20, 1e21, 1e22
+        }
     };
 
     const char* p = first;
@@ -7991,14 +7995,14 @@ bool parse_float_fast(const char* first, const char* last, DecimalPointType deci
         return false; // significand not exactly representable as double
     }
 
-    double result = static_cast<double>(significand);
+    auto result = static_cast<double>(significand);
     if (scale >= 0)
     {
         if (JSON_HEDLEY_UNLIKELY(scale > 22))
         {
             return false;
         }
-        result *= powers_of_ten[scale];
+        result *= powers_of_ten[static_cast<std::size_t>(scale)];
     }
     else
     {
@@ -8006,7 +8010,7 @@ bool parse_float_fast(const char* first, const char* last, DecimalPointType deci
         {
             return false;
         }
-        result /= powers_of_ten[-scale];
+        result /= powers_of_ten[static_cast<std::size_t>(-scale)];
     }
     out = negative ? -result : result;
     return true;