From eeaf52ca86b9422d146e112bc62dc944fc63d899 Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Tue, 6 Jan 2026 00:30:40 -0500
Subject: [PATCH] xo-arena: annex cmpresult.*pp from xo-alloc2

---
 cmake/xo_arenaConfig.cmake.in  |  1 +
 include/xo/arena/cmpresult.hpp | 87 ++++++++++++++++++++++++++++++++++
 src/arena/CMakeLists.txt       |  2 +
 src/arena/cmpresult.cpp        | 38 +++++++++++++++
 4 files changed, 128 insertions(+)
 create mode 100644 include/xo/arena/cmpresult.hpp
 create mode 100644 src/arena/cmpresult.cpp

diff --git a/cmake/xo_arenaConfig.cmake.in b/cmake/xo_arenaConfig.cmake.in
index 3b32fb0..1700fb8 100644
--- a/cmake/xo_arenaConfig.cmake.in
+++ b/cmake/xo_arenaConfig.cmake.in
@@ -7,6 +7,7 @@ include(CMakeFindDependencyMacro)
 #       in CMakeLists.txt
 #
 find_dependency(xo_reflectutil)
+find_dependency(indentlog)
 
 include("${CMAKE_CURRENT_LIST_DIR}/@PROJECT_NAME@Targets.cmake")
 check_required_components("@PROJECT_NAME@")
diff --git a/include/xo/arena/cmpresult.hpp b/include/xo/arena/cmpresult.hpp
new file mode 100644
index 0000000..0a9a911
--- /dev/null
+++ b/include/xo/arena/cmpresult.hpp
@@ -0,0 +1,87 @@
+/** @file cmpresult.hpp
+*
+ *  @author Roland Conybeare, Dec 2025
+ **/
+
+#pragma once
+
+#include <iostream>
+#include <cstdint>
+
+namespace xo {
+    namespace mm {
+        enum class comparison : int32_t {
+            invalid      = -1,
+            comparable   =  0,
+            incomparable = +1,
+        };
+
+        extern const char * comparison2str(comparison x);
+
+        inline std::ostream &
+        operator<<(std::ostream & os, comparison x) {
+            os << comparison2str(x);
+            return os;
+        }
+
+        /** Result of a generic comparison operation
+         **/
+        struct cmpresult {
+            /** @defgroup mm-cmpresult-ctors cmpresult ctors **/
+            ///@{
+            cmpresult() : err_{comparison::invalid}, cmp_{0} {}
+            cmpresult(comparison err, std::int16_t cmp) : err_{err}, cmp_{cmp} {}
+
+            static cmpresult incomparable() { return cmpresult(comparison::incomparable,  0); }
+            static cmpresult       lesser() { return cmpresult(comparison::comparable,   -1); }
+            static cmpresult        equal() { return cmpresult(comparison::comparable,    0); }
+            static cmpresult      greater() { return cmpresult(comparison::comparable,   +1); }
+            template<typename T>
+            static cmpresult from_cmp(T && x, T && y) {
+                if (x < y)
+                    return cmpresult::lesser();
+                else if (x == y)
+                    return cmpresult::equal();
+                else
+                    return cmpresult::greater();
+            }
+
+            ///@}
+
+            /** @defgroup mm-cmpresult-methods cmpresult methods **/
+            ///@{
+
+            /** print to stream **/
+            void display(std::ostream & os) const;
+
+            bool is_lesser() const {
+                return (err_ == comparison::comparable) && (cmp_ < 0);
+            }
+            bool is_equal() const {
+                return (err_ == comparison::comparable) && (cmp_ == 0);
+            }
+            ///@}
+
+            /** @defgroup mm-cmpresult-instance-vars cmpresult instance vars **/
+            ///@{
+            /** -1 -> invalid (sentinel)
+             *   0 -> comparable
+             *  +1 -> incomparable (e.g. iterators from different arenas)
+             **/
+            comparison   err_ = comparison::invalid;
+            /** <0 -> lesser; 0 -> equal, >0 -> greater **/
+            std::int16_t cmp_ = 0;
+            ///@}
+        };
+
+        inline std::ostream & operator<<(std::ostream & os,
+                                         const cmpresult & x)
+        {
+            x.display(os);
+            return os;
+        }
+
+    } /*namespace mm*/
+} /*namespace xo*/
+
+/* end cmpresult.hpp */
diff --git a/src/arena/CMakeLists.txt b/src/arena/CMakeLists.txt
index 345e9cc..4097723 100644
--- a/src/arena/CMakeLists.txt
+++ b/src/arena/CMakeLists.txt
@@ -5,6 +5,7 @@ set(SELF_SRCS
     AllocError.cpp
     AllocInfo.cpp
     ArenaConfig.cpp
+    cmpresult.cpp
 )
 
 xo_add_shared_library4(${SELF_LIB} ${PROJECT_NAME}Targets ${PROJECT_VERSION} 1 ${SELF_SRCS})
@@ -17,5 +18,6 @@ xo_install_include_tree3(include/xo/arena)
 #       xo-arena/cmake/xo_arenaConfig.cmake.in
 
 xo_dependency(${SELF_LIB} xo_reflectutil)
+xo_dependency(${SELF_LIB} indentlog)
 
 # end src/CMakeLists.txt
diff --git a/src/arena/cmpresult.cpp b/src/arena/cmpresult.cpp
new file mode 100644
index 0000000..cd7c299
--- /dev/null
+++ b/src/arena/cmpresult.cpp
@@ -0,0 +1,38 @@
+/** @file cmpresult.cpp
+ *
+ *  @author Roland Conybeare, Dec 2025
+ **/
+
+#include "cmpresult.hpp"
+#include <xo/indentlog/print/tag.hpp>
+#include <iostream>
+
+namespace xo {
+    namespace mm {
+        const char *
+        comparison2str(comparison x)
+        {
+            switch (x) {
+            case comparison::invalid:
+                break;
+            case comparison::comparable:
+                return "cmp";
+            case comparison::incomparable:
+                return "!cmp";
+            }
+
+            return "?comparison";
+        }
+
+        void
+        cmpresult::display(std::ostream & os) const
+        {
+            os << "<cmpresult "
+               << xtag("err", err_)
+               << xtag("cmp", cmp_)
+               << ">";
+        }
+    } /*namespace mm*/
+} /*namespace xo*/
+
+/* end cmpresult.cpp */