From 574a62e66d865765f83fd9c8b3c18736495f16ed Mon Sep 17 00:00:00 2001
From: evoskuil <eric@voskuil.org>
Date: Tue, 28 Jan 2025 20:09:11 -0500
Subject: [PATCH] Remove obsolete workaround for lack of std::views::reverse.

---
 include/bitcoin/system/boost.hpp              | 10 ----------
 include/bitcoin/system/impl/radix/base_16.ipp |  3 ++-
 src/chain/block.cpp                           |  3 ++-
 src/chain/chain_state.cpp                     |  3 ++-
 4 files changed, 6 insertions(+), 13 deletions(-)

diff --git a/include/bitcoin/system/boost.hpp b/include/bitcoin/system/boost.hpp
index 172aaf9433..e5c89bbfd1 100644
--- a/include/bitcoin/system/boost.hpp
+++ b/include/bitcoin/system/boost.hpp
@@ -55,16 +55,6 @@
 ////#include <boost/predef.h>  // platform identifications
 #include <boost/program_options.hpp>
 
-// C++20 suport for ranges not yet available on other platforms.
-#if defined(HAVE_RANGES)
-    #include <ranges>
-    #define views_reverse std::views::reverse
-#else
-    // boost::adaptors::reverse is not constexpr.
-    #include <boost/range/adaptor/reversed.hpp>
-    #define views_reverse boost::adaptors::reverse
-#endif
-
 // ADL free functions for use with boost-json.
 #define DECLARE_JSON_VALUE_CONVERTORS(name) \
 BC_API name tag_invoke(boost::json::value_to_tag<name>, \
diff --git a/include/bitcoin/system/impl/radix/base_16.ipp b/include/bitcoin/system/impl/radix/base_16.ipp
index 17a87f7705..b2f5c60b3f 100644
--- a/include/bitcoin/system/impl/radix/base_16.ipp
+++ b/include/bitcoin/system/impl/radix/base_16.ipp
@@ -20,6 +20,7 @@
 #define LIBBITCOIN_SYSTEM_RADIX_BASE_16_IPP
 
 #include <algorithm>
+#include <ranges>
 #include <string>
 #include <string_view>
 #include <bitcoin/system/data/data.hpp>
@@ -116,7 +117,7 @@ SRCONSTEXPR std::string encode_hash(const data_slice& hash) NOEXCEPT
     auto digit = out.begin();
 
     // views_reverse is RCONSTEXPR
-    for (const auto byte: views_reverse(hash))
+    for (const auto byte: std::views::reverse(hash))
     {
         *digit++ = to_base16_character(shift_right(byte, to_half(byte_bits)));
         *digit++ = to_base16_character(bit_and(byte, 0x0f_u8));
diff --git a/src/chain/block.cpp b/src/chain/block.cpp
index 33dff1d784..31c05c7f5a 100644
--- a/src/chain/block.cpp
+++ b/src/chain/block.cpp
@@ -22,6 +22,7 @@
 #include <iterator>
 #include <memory>
 #include <numeric>
+#include <ranges>
 #include <set>
 #include <type_traits>
 #include <utility>
@@ -619,7 +620,7 @@ bool block::is_invalid_witness_commitment() const NOEXCEPT
     // Last output of commitment pattern holds the committed value (bip141).
     hash_digest reserved{}, committed{};
     if (coinbase->inputs_ptr()->front()->reserved_hash(reserved))
-        for (const auto& output: views_reverse(*coinbase->outputs_ptr()))
+        for (const auto& output: std::views::reverse(*coinbase->outputs_ptr()))
             if (output->committed_hash(committed))
                 if (committed == sha256::double_hash(
                     generate_merkle_root(true), reserved))
diff --git a/src/chain/chain_state.cpp b/src/chain/chain_state.cpp
index 57f5f307aa..9b9b417751 100644
--- a/src/chain/chain_state.cpp
+++ b/src/chain/chain_state.cpp
@@ -21,6 +21,7 @@
 #include <algorithm>
 #include <chrono>
 #include <iterator>
+#include <ranges>
 #include <bitcoin/system/chain/block.hpp>
 #include <bitcoin/system/chain/chain_state.hpp>
 #include <bitcoin/system/chain/checkpoint.hpp>
@@ -451,7 +452,7 @@ uint32_t chain_state::easy_work_required(const data& values,
     const auto& bits = values.bits.ordered;
 
     // Reverse iterate the ordered-by-height list of header bits.
-    for (auto bit: views_reverse(bits))
+    for (auto bit: std::views::reverse(bits))
     {
         if (is_retarget_or_non_limit(--height, bit, retargeting_interval,
             proof_of_work_limit))