From b4c3ba4dda9409887d04a100524d1dac899b9914 Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Fri, 5 Apr 2024 01:37:06 -0400
Subject: [PATCH] xo-unit: + numeric_concept + unit_concept

---
 include/xo/unit/numeric_concept.hpp  | 38 +++++++++++++++++++++
 include/xo/unit/quantity_concept.hpp |  3 +-
 include/xo/unit/unit_concept.hpp     | 49 ++++++++++++++++++++++++++++
 3 files changed, 89 insertions(+), 1 deletion(-)
 create mode 100644 include/xo/unit/numeric_concept.hpp
 create mode 100644 include/xo/unit/unit_concept.hpp

diff --git a/include/xo/unit/numeric_concept.hpp b/include/xo/unit/numeric_concept.hpp
new file mode 100644
index 00000000..720099a3
--- /dev/null
+++ b/include/xo/unit/numeric_concept.hpp
@@ -0,0 +1,38 @@
+/* @file numeric_concept.hpp */
+
+#pragma once
+
+#include <concepts>
+
+namespace xo {
+    namespace unit {
+        /** @concept numeric_concept
+         *  @brief Concept for values that participate in arithmetic operations (+,-,*,/) and comparisons
+         *
+         *  Intended to include at least:
+         *  - built-in integral and floating-point types
+         *  - boost::rational<U>
+         *  - std::complex<U>
+         *  - xo::unit::quantity<U,R>
+         *
+         *  This implies we don't require T to be totally ordered,
+         *  and don't require (<,<=,>=,>) operators.
+         *
+         *  Intend numeric_concept to apply to types suitable for
+         *  xo::unit::quantity::repr_type.
+         **/
+        template <typename T, typename U = T>
+        concept numeric_concept = requires(T x, U y)
+        {
+            { -x };
+            { x - y };
+            { x + y };
+            { x * y };
+            { x / y };
+            { x == y };
+            { x != y };
+        };
+    } /*namespace unit*/
+} /*namespace xo*/
+
+/* end numeric_concept.hpp */
diff --git a/include/xo/unit/quantity_concept.hpp b/include/xo/unit/quantity_concept.hpp
index 09d33446..1235a277 100644
--- a/include/xo/unit/quantity_concept.hpp
+++ b/include/xo/unit/quantity_concept.hpp
@@ -2,7 +2,8 @@
 
 #pragma once
 
-#include <concepts>
+#include "unit_concept.hpp"
+#include "numeric_concept.hpp"
 
 namespace xo {
     namespace unit {
diff --git a/include/xo/unit/unit_concept.hpp b/include/xo/unit/unit_concept.hpp
new file mode 100644
index 00000000..8c5fe59c
--- /dev/null
+++ b/include/xo/unit/unit_concept.hpp
@@ -0,0 +1,49 @@
+/* @file unit_concept.hpp */
+
+#pragma once
+
+#include "dimension_concept.hpp"
+
+namespace xo {
+    namespace unit {
+        /** @brief concept for a Unit type, suitable for use with the quantity template
+         *
+         *  Example:
+         *  @code
+         *  using namespace xo::unit;
+         *  static_assert(unit_concept<units::day>);
+         *  @endcode
+         **/
+        template <typename Unit>
+        concept unit_concept = requires(Unit unit)
+        {
+            typename Unit::scalefactor_type;
+            typename Unit::dim_type;
+            typename Unit::canon_type;
+        }
+            && (ratio_concept<typename Unit::scalefactor_type>
+                && bpu_list_concept<typename Unit::dim_type>
+                && bpu_list_concept<typename Unit::canon_type>);
+
+
+        /** @brief concept for a Unit type, that contains exactly one basis dimension
+         *
+         *  Example:
+         *  @code
+         *  using namespace xo::unit
+         *  static_assert(basis_unit_concept<units::volatility_250d>);
+         *  @endcode
+         **/
+        template <typename Unit>
+        concept basis_unit_concept = requires(Unit unit)
+        {
+            typename Unit::dim_type;
+            typename Unit::dim_type::rest_type;
+        }
+            && (std::same_as<typename Unit::dim_type::rest_type, void>)
+            && (unit_concept<Unit>);
+    } /*namespace unit*/
+} /*namespace xo*/
+
+
+/* end unit_concept.hpp */