Refactor reverse/transpose/cat

In preparation of ViewSmall/ViewBig refactor.

* ra/arrays.hh (ViewSmall): Add members sdim, Dimv. Remove view().
  (ViewBig): Add members sdim, Dimv.
  (reverse, transpose, cat): Write against Slice concept instead of against
  ViewSmall/ViewBig.
* ra/ply.hh (is_iota): Rewrite. Remove unneeded accessory concepts.

Author: lloda

ra/arrays.hh

@@ -310,7 +310,7 @@ static_assert(sizeof(rank_t)>=4 && sizeof(rank_t)>=sizeof(int) && sizeof(dim_t)>
 static_assert(std::is_signed_v<rank_t> && std::is_signed_v<dim_t>);
 
 constexpr struct none_t {} none; // in constructors: don't initialize
-struct noarg { noarg() = delete; }; // in constructors: don't instantiate
+template <class T=void> struct noarg { noarg() = delete; }; // in constructors: don't instantiate
 
 constexpr bool inside(dim_t i, dim_t b) { return 0<=i && i<b; }
 constexpr bool any(bool const x) { return x; } // extended in ra.hh

ra/base.hh

@@ -317,14 +317,6 @@ ptr(P && p, N && n=N {}, S && s=S(maybe_step<S>))
     }
 }
 
-template <class I, class N, class S, class K=ic_t<dim_t(0)>>
-constexpr auto
-reverse(Ptr<Seq<I>, N, S> const & i, K k = {})
-{
-    static_assert(UNB!=i.len_s(0), "Bad arguments to reverse.");
-    return ptr(Seq { i.data().i+(i.dimv[0].len-1)*i.dimv[0].step }, i.dimv[0].len, csub(ic<0>, i.dimv[0].step));
-}
-
 constexpr auto iter(is_fov auto && a) { return ra::ptr(RA_FW(a)); }
 template <class T> constexpr auto iter(std::initializer_list<T> a) { return ra::ptr(a.begin(), a.size()); }
 

ra/expr.hh

@@ -345,9 +345,7 @@ ii(ra::ilist_t<i ...>, T o=0)
 }
 
 template <class A> concept is_ptr = requires (A a) { []<class I, class N, class S>(Ptr<Seq<I>, N, S> const &){}(a); };
-template <class A> concept is_iota_static = requires (A a) { []<class I, class Dimv>(ViewSmall<Seq<I>, Dimv> const &){}(a); };
-template <class A> concept is_iota_dynamic = requires (A a) { []<class I, rank_t RANK>(ViewBig<Seq<I>, RANK> const &){}(a); };
-template <class A> concept is_iota = (is_ptr<A> || is_iota_dynamic<A> || is_iota_static<A>);
+template <class A> concept is_iota = (Slice<A> && requires (A a) { []<class I>(Seq<I> const &){}(a.data()); });
 template <class A> concept is_scalar_index = is_ra_0<A>;
 
 // beaten, whole or piecewise. Presize bv/ds not to need push_back

ra/ply.hh

@@ -24,8 +24,8 @@
 #endif
 
 // ADL with explicit template args. See http://stackoverflow.com/questions/9838862.
-template <int A> constexpr void iter(ra::noarg);
-template <class T> constexpr void cast(ra::noarg);
+template <int A> constexpr void iter(ra::noarg<>);
+template <class T> constexpr void cast(ra::noarg<>);
 
 
 // ---------------------------

ra/ra.hh

@@ -56,10 +56,10 @@ int main()
     {
         cout << sizeof(std::array<ra::none_t, 9> {}) << endl;
         cout << sizeof(ra::none_t [9]) << endl;
-        cout << sizeof(ra::noarg [9]) << endl;
+        cout << sizeof(ra::noarg<> [9]) << endl;
         cout << sizeof(std::array<ra::none_t, 0> {}) << endl;
         cout << sizeof(ra::none_t [0]) << endl;
-        cout << sizeof(ra::noarg [0]) << endl;
+        cout << sizeof(ra::noarg<> [0]) << endl;
         cout << sizeof(ra::Small<int, 0>) << endl;
         cout << sizeof(ra::Small<ra::none_t, 0>) << endl;
         cout << sizeof(ra::Small<noargx, 0>) << endl;