[lmi-commits] [lmi] odd/concepts_smf 315b931e 1/2: Begin to use 'concepts'

[Greg Chicares]

branch: odd/concepts_smf
commit 315b931edb4cef0671cdeef31eb40aab9354a2a5
Author: Gregory W. Chicares <gchicares@sbcglobal.net>
Commit: Gregory W. Chicares <gchicares@sbcglobal.net>

    Begin to use 'concepts'
    
    This commit is much like the idea sketched here:
      https://lists.nongnu.org/archive/html/lmi/2022-07/msg00108.html
    
    It seems at least arguably useful to explain why a request to move is
    fulfilled by copying.
---
 currency.hpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/currency.hpp b/currency.hpp
index d0338185..c4175abe 100644
--- a/currency.hpp
+++ b/currency.hpp
@@ -24,10 +24,14 @@
 
 #include "config.hpp"
 
+#include "smf.hpp"                      // well_move_*<>
+
 #include <cmath>                        // rint()
+#include <concepts>
 #include <limits>
 #include <ostream>
 #include <stdexcept>                    // runtime_error
+#include <type_traits>
 #include <vector>
 
 class raw_cents {}; // Tag class.
@@ -45,6 +49,7 @@ class currency
 
   public:
     using data_type = double;
+    static_assert(std::is_arithmetic_v<data_type>);
 
     currency() = default;
     currency(currency const&) = default;
@@ -68,6 +73,12 @@ class currency
 
     data_type m_ = {};
 };
+// Becomes 'regular' below, once equality operators are defined.
+static_assert(std::semiregular<currency>);
+// Move operations deliberately not defined because there is only one
+// data member and it is of a builtin arithmetic type.
+static_assert(!well_move_assignable<currency>);
+static_assert(!well_move_constructible<currency>);
 
 consteval currency operator""_cents(unsigned long long int cents)
 {
@@ -93,6 +104,8 @@ inline bool operator<=(currency lhs, currency rhs)
 inline bool operator>=(currency lhs, currency rhs)
     {return !operator< (lhs, rhs);}
 
+static_assert(std::regular<currency>);
+
 inline currency operator+(currency lhs, currency rhs)
     {return currency {lhs} += rhs;}
 inline currency operator-(currency lhs, currency rhs)