Cleanups.

Author: pleroy

numerics/elementary_functions_body.hpp

@@ -43,12 +43,12 @@ Product<Q1, Q2> FusedMultiplyAdd(Q1 const& x,
   return x * y + z;
 }
 
-template<typename Q>
+template<cpp_number Q>
 Q Abs(Q const& x) {
   return abs(x);
 }
 
-template<typename Q>
+template<cpp_number Q>
 Q Round(Q const& x) {
   // TODO(phl): This is clunky.  Use `divide_qr` or something.
   return static_cast<Q>(round(static_cast<cpp_bin_float_50>(x)));

quantities/cantor.hpp

@@ -14,7 +14,7 @@ using namespace boost::multiprecision;
 using namespace principia::base::_traits;
 
 // The `cpp_` concepts should be used sparingly, and only in places where the
-// Boost multiprecision API differs from our or from the standard C++ API.  At
+// Boost multiprecision API differs from ours or from the standard C++ API.  At
 // any rate, the multiprecision traits should never be used directly.
 
 template<typename T>
@@ -45,12 +45,11 @@ concept continuum = std::floating_point<T> || cpp_bin_float<T>;
 
 }  // namespace internal
 
+// `cpp_int` and `cpp_rational` are not exported on purpose.
 using internal::continuum;
 using internal::countable;
 using internal::cpp_bin_float;
-using internal::cpp_int;
 using internal::cpp_number;
-using internal::cpp_rational;
 using internal::discrete;
 
 }  // namespace _cantor

quantities/generators_body.hpp

@@ -48,9 +48,9 @@ struct NthRootGenerator<Quantity<D>, n> : not_constructible {
 };
 
 // NOTE(phl): This is designed so that we can write something like `Sqrt(2)`.
-template<typename Q, int n>
-  requires dimensionless<Q>
+template<dimensionless Q, int n>
 struct NthRootGenerator<Q, n> : not_constructible {
+  // TODO(phl): This is not what we want for things like Boost types.
   using Type = double;
 };