find() fixes

include/flux/op/find.hpp

@@ -6,9 +6,11 @@
 #ifndef FLUX_OP_FIND_HPP_INCLUDED
 #define FLUX_OP_FIND_HPP_INCLUDED
 
+#include <flux/core/utils.hpp>
 #include <flux/op/for_each_while.hpp>
-#include <type_traits>
+
 #include <cstring>
+#include <type_traits>
 
 namespace flux {
 
@@ -29,17 +31,23 @@ struct find_fn {
     constexpr auto operator()(Seq&& seq, Value const& value) const
         -> cursor_t<Seq>
     {
-        constexpr auto memchr_opt = std::is_integral_v<Value> &&
-            flux::detail::is_any_of<element_t<Seq>, char*, signed char*,
-                unsigned char*, const char*, const signed char*,
-                const unsigned char*>;
+        constexpr auto memchr_opt = flux::contiguous_sequence<Seq> &&
+            flux::sized_sequence<Seq> && std::is_integral_v<Value> &&
+            flux::detail::any_of<value_t<Seq>, char, signed char, unsigned char,
+                const char, const signed char, const unsigned char>;
 
         if constexpr (memchr_opt) {
             if (std::is_constant_evaluated()) {
                 return impl(seq, value);
-            } else {
-                std::memchr(flux::data(seq), value, flux::usize(seq));
             }
+            auto location = std::memchr(flux::data(seq), value,
+                flux::usize(seq) * sizeof(value_t<Seq>));
+            if (location == nullptr)
+                return flux::usize(seq);
+            else
+                return static_cast<const value_t<Seq>*>(location) -
+                    flux::data(seq);
+
         } else {
             return impl(seq, value);
         }

test/test_find.cpp

@@ -78,4 +78,9 @@ TEST_CASE("find")
         REQUIRE(idx == std::ssize(vec));
     }
 
+    {
+        std::string_view str = "abcdefg";
+        auto idx = flux::find(str, 'd');
+        REQUIRE(idx == 3);
+    }
 }