Reorder declarations, looking to replace Ptr()

* ra/small.hh (Wlen): Move after all Iterators have been defined.
  (start(is_builtin_array)): Use Cell<> directly.
* ra/expr.hh (wlen): Move together with Len, Wlen forward decl.

Author: lloda

ra/expr.hh

@@ -60,7 +60,7 @@ namespace ra {
     constexpr TYPE(TYPE && x) = default;                                \
     constexpr TYPE(TYPE const & x) = default;
 
-// Contextual len: a unique object. See wlen in ply.hh.
+// Contextual len: a unique object. See wlen in small.hh.
 
 constexpr struct Len
 {
@@ -81,6 +81,20 @@ template <class E> struct WLen;                                // defined in ply
 template <class E> concept has_len = requires(int ln, E && e) { WLen<std::decay_t<E>>::f(ln, RA_FW(e)); };
 template <has_len E> constexpr bool is_special_def<E> = true;  // protect exprs with Len from reduction.
 
+template <class Ln, class E>
+constexpr decltype(auto)
+wlen(Ln ln, E && e)
+{
+    static_assert(std::is_integral_v<Ln> || is_constant<Ln>);
+    if constexpr (has_len<E>) {
+        return WLen<std::decay_t<E>>::f(ln, RA_FW(e));
+    } else {
+        return RA_FW(e);
+    }
+}
+
+// Sequence iterator.
+
 template <class I>
 struct Seq
 {

ra/ply.hh

@@ -16,63 +16,6 @@
 
 namespace ra {
 
-
-// ---------------------
-// replace Len in expr tree. VAL arguments that must be either is_constant or is_scalar.
-// ---------------------
-
-template <class Ln, class E>
-constexpr decltype(auto)
-wlen(Ln ln, E && e)
-{
-    static_assert(std::is_integral_v<Ln> || is_constant<Ln>);
-    if constexpr (has_len<E>) {
-        return WLen<std::decay_t<E>>::f(ln, RA_FW(e));
-    } else {
-        return RA_FW(e);
-    }
-}
-
-template <>
-struct WLen<Len>
-{
-    constexpr static auto
-    f(auto ln, auto && e) { return Scalar {ln}; }
-};
-
-template <class Op, Iterator ... P, int ... I> requires (has_len<P> || ...)
-struct WLen<Map<Op, std::tuple<P ...>, ilist_t<I ...>>>
-{
-    constexpr static auto
-    f(auto ln, auto && e) { return map_(RA_FW(e).op, wlen(ln, std::get<I>(RA_FW(e).t)) ...); }
-};
-
-template <Iterator ... P, int ... I> requires (has_len<P> || ...)
-struct WLen<Pick<std::tuple<P ...>, ilist_t<I ...>>>
-{
-    constexpr static auto
-    f(auto ln, auto && e) { return pick(wlen(ln, std::get<I>(RA_FW(e).t)) ...); }
-};
-
-template <class I> requires (has_len<I>)
-struct WLen<Seq<I>>
-{
-    constexpr static auto
-    f(auto ln, auto && e) { return Seq { VAL(wlen(ln, e.i)) }; }
-};
-
-template <class I, class N, class S> requires (has_len<I> || has_len<N> || has_len<S>)
-struct WLen<Ptr<I, N, S>>
-{
-    constexpr static auto
-    f(auto ln, auto && e) { return Ptr(wlen(ln, e.cp), VAL(wlen(ln, e.n)), VAL(wlen(ln, e.s))); }
-};
-
-
-// --------------
-// ply
-// --------------
-
 struct Nop {};
 
 // run time order/rank.