From 684c416f908fce586dcfd6edb7680a26f1ac9f28 Mon Sep 17 00:00:00 2001
From: Wim Haeck <whaeck@gmail.com>
Date: Thu, 20 Jun 2024 21:50:34 -0600
Subject: [PATCH] fixing the last issues in zip_transform

---
 .../std23/views/test/zip_transform.test.cpp    | 18 +++++++++---------
 src/tools/std23/views/zip_transform.hpp        | 12 +++++++++++-
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/src/tools/std23/views/test/zip_transform.test.cpp b/src/tools/std23/views/test/zip_transform.test.cpp
index b545678..331ea53 100644
--- a/src/tools/std23/views/test/zip_transform.test.cpp
+++ b/src/tools/std23/views/test/zip_transform.test.cpp
@@ -76,7 +76,7 @@ SCENARIO( "zip_view" ) {
         CHECK( std20::ranges::bidirectional_range< Range > );
         CHECK( ! std20::ranges::random_access_range< Range > );
         CHECK( ! std20::ranges::contiguous_range< Range > );
-//        CHECK( std20::ranges::common_range< Range > );
+        CHECK( ! std20::ranges::common_range< Range > );
       }
 
       THEN( "a stride_view can be constructed and members can be tested" ) {
@@ -112,7 +112,7 @@ SCENARIO( "zip_view" ) {
         CHECK( std20::ranges::sized_range< Range > );
         CHECK( std20::ranges::forward_range< Range > );
         CHECK( std20::ranges::bidirectional_range< Range > );
-//        CHECK( std20::ranges::random_access_range< Range > );
+        CHECK( std20::ranges::random_access_range< Range > );
         CHECK( ! std20::ranges::contiguous_range< Range > );
         CHECK( std20::ranges::common_range< Range > );
       }
@@ -129,13 +129,13 @@ SCENARIO( "zip_view" ) {
         CHECK( equal[0] == chunk.front() );
         CHECK( equal[6] == chunk.back() );
 
-//        CHECK( 26 == chunk[0] );
-//        CHECK( 29 == chunk[1] );
-//        CHECK( 32 == chunk[2] );
-//        CHECK( 35 == chunk[3] );
-//        CHECK( 38 == chunk[4] );
-//        CHECK( 41 == chunk[5] );
-//        CHECK( 44 == chunk[6] );
+        CHECK( 26 == chunk[0] );
+        CHECK( 29 == chunk[1] );
+        CHECK( 32 == chunk[2] );
+        CHECK( 35 == chunk[3] );
+        CHECK( 38 == chunk[4] );
+        CHECK( 41 == chunk[5] );
+        CHECK( 44 == chunk[6] );
       } // THEN
     } // WHEN
   } // GIVEN
diff --git a/src/tools/std23/views/zip_transform.hpp b/src/tools/std23/views/zip_transform.hpp
index 32a826e..7f7c362 100644
--- a/src/tools/std23/views/zip_transform.hpp
+++ b/src/tools/std23/views/zip_transform.hpp
@@ -213,6 +213,16 @@ private :
 
       return iterator{ left } -= n;
     }
+
+    template < typename B = Base >
+    friend constexpr auto operator-( const iterator& left, const iterator& right )
+    -> std::enable_if_t<
+        std20::ranges::sized_sentinel_for< std20::ranges::iterator_t< B >,
+                                           std20::ranges::iterator_t< B > >,
+        difference_type > {
+
+      return left.current_ - right.current_;
+    }
   };
 
   template < bool Const >
@@ -277,7 +287,7 @@ private :
     -> std::enable_if_t< std20::ranges::sized_sentinel_for< InnerSentinel< Const >, InnerIterator< Other > >,
                          std20::ranges::range_difference_t< maybe_const< Other, InnerView > > > {
 
-      return right - left;
+      return -( right - left );
     }
   };