diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6499816d..bd1c1eaa 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -294,6 +294,7 @@ list (
     colour.hpp
     concepts.hpp
     concepts/clock.hpp
+    concepts/string.hpp
     container.hpp
     coord.hpp
     coord/fwd.hpp
diff --git a/cast.hpp b/cast.hpp
index 07177a0f..0ae2b779 100644
--- a/cast.hpp
+++ b/cast.hpp
@@ -9,7 +9,7 @@
 #pragma once
 
 
-#include "concepts.hpp"
+#include "concepts/traits.hpp"
 #include "debug/assert.hpp"
 #include "platform.hpp"
 
@@ -74,8 +74,8 @@ namespace cruft::cast {
     /// Identity casts are allowed so as to simplify the use of this routine
     /// in template code.
     template <
-        concepts::arithmetic NarrowT,
-        concepts::arithmetic WideT
+        concepts::traits::arithmetic NarrowT,
+        concepts::traits::arithmetic WideT
     >
     requires
         (std::is_signed_v<NarrowT> == std::is_signed_v<WideT>) &&
@@ -150,8 +150,8 @@ namespace cruft::cast {
     ///
     /// Runtime checks will be compiled out if NDEBUG is defined.
     template <
-        concepts::pointer DstT,
-        concepts::pointer SrcT
+        concepts::traits::pointer DstT,
+        concepts::traits::pointer SrcT
     >
     DstT
     alignment (SrcT src)
@@ -172,7 +172,7 @@ namespace cruft::cast {
     /// the converted value. Note: this is only a debug-time check and is
     /// compiled out in optimised builds.
     template <
-        concepts::pointer T,
+        concepts::traits::pointer T,
         typename V
     >
     T
@@ -188,7 +188,7 @@ namespace cruft::cast {
 
     //-------------------------------------------------------------------------
     template <
-        concepts::reference T,
+        concepts::traits::reference T,
         typename V
     >
     T
diff --git a/cmdopt2/arg.hpp b/cmdopt2/arg.hpp
index 12ec245f..12a9508d 100644
--- a/cmdopt2/arg.hpp
+++ b/cmdopt2/arg.hpp
@@ -38,7 +38,7 @@ namespace cruft::cmdopt2 {
         bind (ValueT &ref)
         {
             CHECK (!acceptor1);
-            if constexpr (std::is_same_v<ValueT, std::string>) {
+            if constexpr (std::is_same_v<ValueT, std::string> or std::is_same_v<ValueT, char const*>) {
                 acceptor1 = [&ref] (std::string_view str) { ref = str; };
             } else {
                 acceptor1 = [&ref] (std::string_view str) { ref = parse::from_string<ValueT> (str); };
diff --git a/cmdopt2/parser.cpp b/cmdopt2/parser.cpp
index 31a34a54..b1ac372c 100644
--- a/cmdopt2/parser.cpp
+++ b/cmdopt2/parser.cpp
@@ -1,5 +1,7 @@
 #include "./parser.hpp"
 
+#include "./arg.hpp"
+
 using cruft::cmdopt2::parser;
 
 
diff --git a/cmdopt2/parser.hpp b/cmdopt2/parser.hpp
index 8f46dd35..87ac2090 100644
--- a/cmdopt2/parser.hpp
+++ b/cmdopt2/parser.hpp
@@ -8,7 +8,7 @@
 
 #pragma once
 
-#include "./arg.hpp"
+#include "./fwd.hpp"
 
 #include <iosfwd>
 #include <vector>
diff --git a/concepts.hpp b/concepts.hpp
index 785d922f..65dd727b 100644
--- a/concepts.hpp
+++ b/concepts.hpp
@@ -8,268 +8,12 @@
 
 #pragma once
 
-#include <type_traits>
-#include <iterator>
-#include <utility>
-#include <functional>
+#include "concepts/named.hpp"
 
-
-///////////////////////////////////////////////////////////////////////////////
-/// A minimal implementation of the standard concept library for use with
-/// compilers that lack it.
-///
-/// Portions of this code are adapted from the standard and as such do not
-/// fall under the top copyright notice.
-///
-/// clang#xxx: Remove me when clang includes an implementation of these.
-namespace cruft::concepts {
-    template <typename T>
-    concept floating_point = std::is_floating_point_v<T>;
-
-    template <typename T>
-    concept integral = std::is_integral_v<T>;
-
-    template <typename T>
-    concept signed_integral = integral<T> && std::is_signed_v<T>;
-
-    template <typename T>
-    concept unsigned_integral = integral<T> && std::is_unsigned_v<T>;
-
-    template <typename T>
-    concept destructible = std::is_nothrow_destructible_v<T>;
-
-    template <class T, typename ...ArgsT>
-    concept constructible_from = destructible<T> && std::is_constructible_v<T, ArgsT...>;
-
-    template <class T>
-    concept default_constructible = constructible_from<T>;
-
-    template <class T>
-    concept copy_constructible = std::is_copy_constructible_v<T>;
-
-    template <class T>
-    concept move_constructible = std::is_move_constructible_v<T>;
-
-
-    template <typename A, typename B>
-    concept same_as = std::is_same_v<A, B> and std::is_same_v<B, A>;
-
-
-    template <typename From, typename To>
-    concept convertible_to =
-        std::is_convertible_v<From, To> &&
-        requires (From (&f)())
-    {
-        static_cast<To> (f());
-    };
-
-
-    template <
-        typename LHS,
-        typename RHS
-    >
-    concept assignable_from =
-        std::is_lvalue_reference_v<LHS> &&
-        // clang#xxx: common_reference_t is too annoying to implement as
-        // a temporary fix for this temporary fix. Reintroduce this when
-        // clang knows about common_reference_t.
-        // std::common_reference_with<
-        //     std::remove_reference_t<LHS> const&,
-        //     std::remove_reference_t<RHS> const&
-        // > &&
-        requires(LHS lhs, RHS&& rhs)
-    {
-        { lhs = std::forward<RHS>(rhs) } -> same_as<LHS>;
-    };
-
-
-    template <typename T>
-    concept swappable = requires (T &&a, T &&b) { std::swap (a, b); };
-
-
-    template < class T >
-    concept movable =
-      std::is_object_v<T> &&
-      move_constructible<T> &&
-      assignable_from<T&, T> &&
-      swappable<T>;
-
-
-    template <typename T>
-    concept boolean =
-        movable<std::remove_cvref_t<T>> &&
-        requires (
-            std::remove_reference_t<T> const& b1,
-            std::remove_reference_t<T> const& b2,
-            bool const a
-        )
-    {
-        {  b1 } -> convertible_to<bool>;
-        { !b1 } -> convertible_to<bool>;
-
-        { b1 && b2 } -> same_as<bool>;
-        { b1 &&  a } -> same_as<bool>;
-        {  a && b2 } -> same_as<bool>;
-        { b1 || b2 } -> same_as<bool>;
-        { b1 ||  a } -> same_as<bool>;
-        {  a || b2 } -> same_as<bool>;
-
-        { b1 == b2 } -> convertible_to<bool>;
-        { b1 ==  a } -> convertible_to<bool>;
-        {  a == b2 } -> convertible_to<bool>;
-        { b1 != b2 } -> convertible_to<bool>;
-        { b1 !=  a } -> convertible_to<bool>;
-        {  a != b2 } -> convertible_to<bool>;
-    };
-
-
-    template <typename T>
-    concept equality_comparable =
-        requires (
-            std::remove_reference_t<T> const &a,
-            std::remove_reference_t<T> const &b
-        )
-    {
-        { a == b } -> boolean;
-        { a != b } -> boolean;
-        { b == a } -> boolean;
-        { b != a } -> boolean;
-    };
-
-
-    template <typename FunctionT, typename ...ArgsT>
-    concept invocable =
-        requires (FunctionT &&function, ArgsT &&...args)
-    {
-        std::invoke (
-            std::forward<FunctionT> (function),
-            std::forward<ArgsT> (args)...
-        );
-    };
-
-    template <typename FunctionT, typename ...ArgsT>
-    concept regular_invocable = invocable<FunctionT, ArgsT...>;
-
-    template <typename FunctionT, typename ...ArgsT>
-    concept predicate =
-        regular_invocable<FunctionT, ArgsT...> &&
-        boolean<std::invoke_result_t<FunctionT, ArgsT...>>;
-}
-
-
-///////////////////////////////////////////////////////////////////////////////
-// C++ named requirements
-namespace cruft::concepts {
-    /// Corresponds to the "Container" named requirement.
-    template <class T>
-    concept container =
-        default_constructible<T> &&
-        copy_constructible<T> &&
-        move_constructible<T> &&
-        destructible<T> &&
-        equality_comparable<T> &&
-        requires (T a, T b)
-    {
-        typename T::value_type;
-        typename T::reference;
-        typename T::const_reference;
-        typename T::iterator;
-        typename T::const_iterator;
-        typename T::difference_type;
-        typename T::size_type;
-
-        { a = b } -> same_as<T&>;
-        { a = std::move (b) } -> same_as<T&>;
-
-        { a.begin  () } -> same_as<typename T::iterator>;
-        { a.end    () } -> same_as<typename T::iterator>;
-        { a.cbegin () } -> same_as<typename T::const_iterator>;
-        { a.cend   () } -> same_as<typename T::const_iterator>;
-
-        { a.swap (b)  } -> same_as<void>;
-        { std::swap (a, b) } -> same_as<void>;
-
-        { a.size () } -> same_as<typename T::size_type>;
-        { a.max_size () } -> same_as<typename T::size_type>;
-        { a.empty () } -> boolean;
-    };
-
-
-    template <typename T>
-    concept move_assignable =
-        requires (T a, T b)
-    {
-        { a = std::move (b) } -> same_as<T&>;
-    };
-
-
-    template <typename T>
-    concept copy_assignable =
-        move_assignable<T> &&
-        requires (T a, T b)
-    {
-        { a = b } -> same_as<T&>;
-    };
-
-
-    template <typename T>
-    concept legacy_iterator =
-        copy_constructible<T> &&
-        copy_assignable<T> &&
-        destructible<T> &&
-        swappable<T> &&
-        requires (T t)
-    {
-        typename std::iterator_traits<T>::value_type;
-        typename std::iterator_traits<T>::difference_type;
-        typename std::iterator_traits<T>::reference;
-        typename std::iterator_traits<T>::pointer;
-        typename std::iterator_traits<T>::iterator_category;
-
-        {  *t };
-        { ++t } -> same_as<T&>;
-    };
-
-    template <typename T>
-    concept legacy_input_iterator =
-        legacy_iterator<T> &&
-        equality_comparable<T> &&
-        requires (T a, T b)
-    {
-        typename std::iterator_traits<T>::reference;
-        typename std::iterator_traits<T>::value_type;
-        { a != b } -> boolean;
-
-        { ++a } -> same_as<T&>;
-        { a++ };
-    };
-}
-
-
-///////////////////////////////////////////////////////////////////////////////
-// Trivial wrappers around traits
-namespace cruft::concepts {
-    template <typename T>
-    concept arithmetic = std::is_arithmetic_v<T>;
-
-    template <typename T>
-    concept scalar = std::is_scalar_v<T>;
-
-    template <typename T>
-    concept enumeration = std::is_enum_v<T>;
-
-    template <typename T>
-    concept pointer = std::is_pointer_v<T>;
-
-    template <typename T>
-    concept reference = std::is_reference_v<T>;
-}
-
-
-///////////////////////////////////////////////////////////////////////////////
-// Some handy non-standard concepts
+#include <concepts>
 #include <tuple>
 
+
 namespace cruft::concepts {
     /// Tests if the type has all typedefs required for use with
     /// std::iterator_traits.
@@ -301,10 +45,10 @@ namespace cruft::concepts {
     template <typename T>
     concept numeric = requires (T t)
     {
-        {  t * t } -> convertible_to<T>;
-        {  t / t } -> convertible_to<T>;
-        {  t - t } -> convertible_to<T>;
-        {  t + t } -> convertible_to<T>;
+        {  t * t } -> std::convertible_to<T>;
+        {  t / t } -> std::convertible_to<T>;
+        {  t - t } -> std::convertible_to<T>;
+        {  t + t } -> std::convertible_to<T>;
     };
 
 
@@ -312,10 +56,10 @@ namespace cruft::concepts {
     template <typename T>
     concept iterable = requires (T t)
     {
-        { std::begin  (t) } -> legacy_iterator;
-        { std::end    (t) } -> legacy_iterator;
-        { std::cbegin (t) } -> legacy_iterator;
-        { std::cend   (t) } -> legacy_iterator;
+        { std::begin  (t) } -> named::legacy_iterator;
+        { std::end    (t) } -> named::legacy_iterator;
+        { std::cbegin (t) } -> named::legacy_iterator;
+        { std::cend   (t) } -> named::legacy_iterator;
     };
 
 
@@ -326,7 +70,7 @@ namespace cruft::concepts {
         // We should be checking this, but it fails for zero length tuples and
         // it's kind of a low priority right now.
         // { std::tuple_element<0,T> {} };
-        { std::tuple_size<T>::value } -> convertible_to<std::size_t>;
+        { std::tuple_size<T>::value } -> std::convertible_to<std::size_t>;
         { std::tuple_cat (a, b) };
     };
-}
+}
\ No newline at end of file
diff --git a/concepts/named.hpp b/concepts/named.hpp
new file mode 100644
index 00000000..70f3883b
--- /dev/null
+++ b/concepts/named.hpp
@@ -0,0 +1,94 @@
+#pragma once
+
+#include <iterator>
+#include <concepts>
+#include <utility>
+
+
+///////////////////////////////////////////////////////////////////////////////
+// C++ named requirements
+namespace cruft::concepts::named {
+    /// Corresponds to the "Container" named requirement.
+    template <class T>
+    concept container =
+        std::default_initializable<T> and
+        std::copy_constructible<T> and
+        std::move_constructible<T> and
+        std::destructible<T> and
+        std::equality_comparable<T> and
+        requires (T a, T b)
+    {
+        typename T::value_type;
+        typename T::reference;
+        typename T::const_reference;
+        typename T::iterator;
+        typename T::const_iterator;
+        typename T::difference_type;
+        typename T::size_type;
+
+        { a = b } -> std::same_as<T&>;
+        { a = std::move (b) } -> std::same_as<T&>;
+
+        { a.begin  () } -> std::same_as<typename T::iterator>;
+        { a.end    () } -> std::same_as<typename T::iterator>;
+        { a.cbegin () } -> std::same_as<typename T::const_iterator>;
+        { a.cend   () } -> std::same_as<typename T::const_iterator>;
+
+        { a.swap (b)  } -> std::same_as<void>;
+        { std::swap (a, b) } -> std::same_as<void>;
+
+        { a.size () } -> std::same_as<typename T::size_type>;
+        { a.max_size () } -> std::same_as<typename T::size_type>;
+        { a.empty () } -> std::same_as<bool>;
+    };
+
+
+    template <typename T>
+    concept move_assignable =
+    requires (T a, T b)
+    {
+        { a = std::move (b) } -> std::same_as<T&>;
+    };
+
+
+    template <typename T>
+    concept copy_assignable =
+    move_assignable<T> &&
+    requires (T a, T b)
+    {
+        { a = b } -> std::same_as<T&>;
+    };
+
+
+    template <typename T>
+    concept legacy_iterator =
+    std::copy_constructible<T> &&
+    copy_assignable<T> &&
+        std::destructible<T> &&
+    std::swappable<T> &&
+    requires (T t)
+    {
+        typename std::iterator_traits<T>::value_type;
+        typename std::iterator_traits<T>::difference_type;
+        typename std::iterator_traits<T>::reference;
+        typename std::iterator_traits<T>::pointer;
+        typename std::iterator_traits<T>::iterator_category;
+
+        {  *t };
+        { ++t } -> std::same_as<T&>;
+    };
+
+    template <typename T>
+    concept legacy_input_iterator =
+    legacy_iterator<T> &&
+    std::equality_comparable<T> &&
+    requires (T a, T b)
+    {
+        typename std::iterator_traits<T>::reference;
+        typename std::iterator_traits<T>::value_type;
+        { a != b } -> std::same_as<bool>;
+
+        { ++a } -> std::same_as<T&>;
+        { a++ };
+    };
+}
diff --git a/concepts/string.hpp b/concepts/string.hpp
new file mode 100644
index 00000000..a7c2da35
--- /dev/null
+++ b/concepts/string.hpp
@@ -0,0 +1,23 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * Copyright 2022, Danny Robson <danny@nerdcruft.net>
+ */
+
+#pragma once
+
+#include <concepts>
+#include <string>
+#include <string_view>
+
+namespace cruft::concepts {
+    /// A type that behaves like a string. ie, a sequence of characters
+    template <typename T>
+    concept stringy =
+        std::same_as<T, std::string> or
+        std::same_as<T, std::string_view> or
+        std::same_as<T, char const*> or
+        std::same_as<T, char *>;
+}
diff --git a/concepts/traits.hpp b/concepts/traits.hpp
new file mode 100644
index 00000000..5a9d8350
--- /dev/null
+++ b/concepts/traits.hpp
@@ -0,0 +1,23 @@
+#pragma once
+
+#include <type_traits>
+
+
+///////////////////////////////////////////////////////////////////////////////
+// Trivial wrappers around traits
+namespace cruft::concepts::traits {
+    template <typename T>
+    concept arithmetic = std::is_arithmetic_v<T>;
+
+    template <typename T>
+    concept scalar = std::is_scalar_v<T>;
+
+    template <typename T>
+    concept enumeration = std::is_enum_v<T>;
+
+    template <typename T>
+    concept pointer = std::is_pointer_v<T>;
+
+    template <typename T>
+    concept reference = std::is_reference_v<T>;
+}
diff --git a/maths.hpp b/maths.hpp
index 90a4b37e..99622184 100644
--- a/maths.hpp
+++ b/maths.hpp
@@ -12,7 +12,10 @@
 // it triggers a circular dependency; debug -> format -> maths -> debug
 // instead, just use cassert
 
+#include "concepts/traits.hpp"
+#include "concepts/named.hpp"
 #include "concepts.hpp"
+
 #include "types/traits.hpp"
 #include "float.hpp"
 
@@ -36,7 +39,7 @@
 ///////////////////////////////////////////////////////////////////////////////
 namespace cruft {
     ///////////////////////////////////////////////////////////////////////////
-    template <concepts::arithmetic T>
+    template <concepts::traits::arithmetic T>
     constexpr T
     abs [[gnu::const]] (T t)
     {
@@ -151,7 +154,7 @@ namespace cruft {
 
     template <
         typename BaseT,
-        concepts::integral ExponentT
+        std::integral ExponentT
     >
     constexpr BaseT
     pow [[gnu::const]] (BaseT base, ExponentT exponent)
@@ -174,7 +177,7 @@ namespace cruft {
 
 
     //-------------------------------------------------------------------------
-    template <concepts::integral T>
+    template <std::integral T>
     constexpr bool
     is_pow2 [[gnu::const]] (T value)
     {
@@ -188,7 +191,7 @@ namespace cruft {
     ///
     /// `val` must be strictly greater than zero, otherwise the results are
     /// undefined.
-    template <concepts::integral T>
+    template <std::integral T>
     constexpr T
     log2 (T val)
     {
@@ -219,7 +222,7 @@ namespace cruft {
     /// with runtime performance given the simplistic construction.
     ///
     /// It's useful for sizing temporary arrays.
-    template <concepts::integral T>
+    template <std::integral T>
     consteval T
     ilog (T val, T base)
     {
@@ -232,7 +235,7 @@ namespace cruft {
 
     ///////////////////////////////////////////////////////////////////////////////
     /// round T up to the nearest multiple of U
-    template <concepts::integral T, concepts::integral U>
+    template <std::integral T, std::integral U>
     inline
     std::common_type_t<T, U>
     round_up (T value, U size)
@@ -247,7 +250,7 @@ namespace cruft {
 
     ///----------------------------------------------------------------------------
     /// round T up to the nearest power-of-2
-    template <concepts::integral T>
+    template <std::integral T>
     constexpr auto
     round_pow2  (T value)
     {
@@ -265,8 +268,8 @@ namespace cruft {
     ///----------------------------------------------------------------------------
     /// round T up to the nearest multiple of U and return the quotient.
     template <
-        concepts::integral T,
-        concepts::integral U
+        std::integral T,
+        std::integral U
     >
     constexpr auto
     divup  (T const a, U const b)
@@ -277,7 +280,7 @@ namespace cruft {
 
     ///////////////////////////////////////////////////////////////////////////////
     // Properties
-    template <concepts::integral T>
+    template <std::integral T>
     constexpr bool
     is_integer (T)
     {
@@ -285,7 +288,7 @@ namespace cruft {
     }
 
 
-    template <concepts::floating_point T>
+    template <std::floating_point T>
     constexpr bool
     is_integer (T t)
     {
@@ -295,7 +298,7 @@ namespace cruft {
 
 
     //-------------------------------------------------------------------------
-    template <concepts::integral NumericT>
+    template <std::integral NumericT>
     constexpr auto
     digits10 (NumericT v) noexcept
     {
@@ -325,7 +328,7 @@ namespace cruft {
     }
 
 
-    template <concepts::integral ValueT, concepts::integral BaseT>
+    template <std::integral ValueT, std::integral BaseT>
     constexpr int
     digits (ValueT value, BaseT base) noexcept
     {
@@ -344,7 +347,7 @@ namespace cruft {
 
     ///----------------------------------------------------------------------------
     /// return positive or negative unit value corresponding to the input.
-    template <concepts::signed_integral T>
+    template <std::signed_integral T>
     constexpr T
     sign (T t)
     {
@@ -355,7 +358,7 @@ namespace cruft {
     /// return positive or negative unit value corresponding to the input.
     /// guaranteed to give correct results for signed zeroes, use another
     /// method if extreme speed is important.
-    template <concepts::floating_point T>
+    template <std::floating_point T>
     constexpr T
     sign (T t)
     {
@@ -386,7 +389,7 @@ namespace cruft {
     // Modulus/etc
 
     // namespaced wrapper for `man 3 fmod`
-    template <concepts::floating_point T>
+    template <std::floating_point T>
     constexpr T
     mod (T x, T y)
     {
@@ -394,7 +397,7 @@ namespace cruft {
     }
 
 
-    template <concepts::integral T>
+    template <std::integral T>
     constexpr T
     mod (T x, T y)
     {
@@ -402,7 +405,7 @@ namespace cruft {
     }
 
 
-    template <concepts::floating_point ValueT>
+    template <std::floating_point ValueT>
     ValueT
     frac (ValueT val)
     {
@@ -515,8 +518,8 @@ namespace cruft {
 
     template <typename InputT>
     requires
-        concepts::legacy_input_iterator<InputT> &&
-        concepts::floating_point<typename std::iterator_traits<InputT>::value_type>
+        concepts::named::legacy_input_iterator<InputT> &&
+        std::floating_point<typename std::iterator_traits<InputT>::value_type>
     typename std::iterator_traits<InputT>::value_type
     sum (InputT first, InputT last)
     {
@@ -545,8 +548,8 @@ namespace cruft {
     //-------------------------------------------------------------------------
     template <typename InputT>
     requires
-        concepts::legacy_input_iterator<InputT> &&
-        concepts::integral<typename std::iterator_traits<InputT>::value_type>
+        concepts::named::legacy_input_iterator<InputT> &&
+        std::integral<typename std::iterator_traits<InputT>::value_type>
     typename std::iterator_traits<InputT>::value_type
     sum (InputT first, InputT last)
     {
@@ -575,7 +578,7 @@ namespace cruft {
     /// parameter packs.
     ///
     /// eg, `max (sizeof (T)...)` will otherwise fail with a single type.
-    template <concepts::integral ValueT>
+    template <std::integral ValueT>
     constexpr decltype(auto)
     max (ValueT &&val)
     {
@@ -598,7 +601,7 @@ namespace cruft {
 
 
     //-------------------------------------------------------------------------
-    template <concepts::container ContainerT>
+    template <concepts::named::container ContainerT>
     typename ContainerT::value_type const&
     max (ContainerT const &vals)
     {
@@ -606,13 +609,13 @@ namespace cruft {
     }
 
 
-    template <concepts::container ValueT>
+    template <concepts::named::container ValueT>
     typename ValueT::value_type &
     max (ValueT &&) = delete;
 
 
     //-------------------------------------------------------------------------
-    template <concepts::container ContainerT>
+    template <concepts::named::container ContainerT>
     typename ContainerT::value_type const&
     min (ContainerT const &vals)
     {
@@ -620,7 +623,7 @@ namespace cruft {
     }
 
 
-    template <concepts::container ContainerT>
+    template <concepts::named::container ContainerT>
     typename ContainerT::value_type&
     min (ContainerT &&) = delete;
 
@@ -643,9 +646,9 @@ namespace cruft {
 
     // min/max clamping
     template <
-        concepts::scalar T,
-        concepts::scalar U,
-        concepts::scalar V
+        concepts::traits::scalar T,
+        concepts::traits::scalar U,
+        concepts::traits::scalar V
     >
     constexpr std::common_type_t<T,U,V>
     clamp (T const val, U const lo, V const hi)
@@ -697,8 +700,8 @@ namespace cruft {
 
     // uint -> float
     template <
-        concepts::unsigned_integral T,
-        concepts::floating_point U
+        std::unsigned_integral T,
+        std::floating_point U
     >
     constexpr U
     renormalise (T t)
@@ -710,8 +713,8 @@ namespace cruft {
     //-------------------------------------------------------------------------
     // float -> uint
     template <
-        concepts::floating_point T,
-        concepts::unsigned_integral U
+        std::floating_point T,
+        std::unsigned_integral U
     >
     constexpr U
     renormalise (T t)
@@ -745,8 +748,8 @@ namespace cruft {
     // ambiguous overloads
     template <typename T, typename U>
     requires
-        concepts::floating_point<T> &&
-        concepts::floating_point<U> &&
+        std::floating_point<T> &&
+        std::floating_point<U> &&
         (!std::is_same_v<T, U>)
     constexpr U
     renormalise (T t)
@@ -759,8 +762,8 @@ namespace cruft {
     // hi_uint -> lo_uint
     template <typename T, typename U>
     requires
-        concepts::unsigned_integral<T> &&
-        concepts::unsigned_integral<U> &&
+        std::unsigned_integral<T> &&
+        std::unsigned_integral<U> &&
         (sizeof (T) > sizeof (U))
     constexpr U
     renormalise (T t)
@@ -781,8 +784,8 @@ namespace cruft {
         typename DstT
     >
     requires
-        concepts::unsigned_integral<SrcT> &&
-        concepts::unsigned_integral<DstT> &&
+        std::unsigned_integral<SrcT> &&
+        std::unsigned_integral<DstT> &&
         (sizeof (SrcT) < sizeof (DstT))
     constexpr DstT
     renormalise (SrcT src)
@@ -834,7 +837,7 @@ namespace cruft {
     // anything-to-sint
     template <typename T, typename U>
     requires
-        concepts::signed_integral<U> &&
+        std::signed_integral<U> &&
         (!std::is_same<T,U>::value)
     constexpr U
     renormalise (T t)
@@ -851,7 +854,7 @@ namespace cruft {
     // sint-to-anything
     template <typename T, typename U>
     requires
-        concepts::signed_integral<T> &&
+        std::signed_integral<T> &&
         (!std::is_same<T,U>::value)
     constexpr U
     renormalise (T sint)
diff --git a/test/concepts.cpp b/test/concepts.cpp
index b1bf955b..ea5e129e 100644
--- a/test/concepts.cpp
+++ b/test/concepts.cpp
@@ -1,12 +1,12 @@
 #include <cruft/util/tap.hpp>
-#include <cruft/util/concepts.hpp>
+#include <cruft/util/concepts/named.hpp>
 
 int main ()
 {
     cruft::TAP::logger tap;
 
-    tap.expect (cruft::concepts::container<std::vector<int>>, "vector is a container");
-    tap.expect (!cruft::concepts::container<int>, "int is not a container");
+    tap.expect (cruft::concepts::named::container<std::vector<int>>, "vector is a container");
+    tap.expect (!cruft::concepts::named::container<int>, "int is not a container");
 
     tap.expect (cruft::concepts::tuple<std::tuple<>>, "tuple<> is a tuple");
     tap.expect (cruft::concepts::tuple<std::tuple<int>>, "tuple<int> is a tuple");
diff --git a/types/tagged.hpp b/types/tagged.hpp
index f14ce306..b65701e0 100644
--- a/types/tagged.hpp
+++ b/types/tagged.hpp
@@ -14,6 +14,7 @@
 #include "../maths.hpp"
 #include "../tuple/type.hpp"
 
+#include <concepts>
 #include <tuple>
 
 
@@ -54,7 +55,7 @@ namespace cruft {
 
         //---------------------------------------------------------------------
         template <typename InitialT>
-        requires (cruft::concepts::same_as<std::remove_cvref_t<InitialT>, ValueT> || ...)
+        requires (std::same_as<std::remove_cvref_t<InitialT>, ValueT> || ...)
         tagged (InitialT &&initial)
         {
             set<InitialT> (std::forward<InitialT> (initial));