Changeset 7491f97

Timestamp:

Nov 14, 2022, 10:57:02 AM (2 years ago)

Author:

Andrew Beach <ajbeach@…>

Branches:

ADT, ast-experimental, master

Children:

19a8c40

Parents:

71806e0

Message:

Renaming and comments in group_iterate_t to help clarity.

File:

• src/Common/utility.h (modified) (2 diffs)

src/Common/utility.h

@@ -461 +461 @@
         Iterables iterables;
 
+        // Getting the iterator and value types this way preserves const.
         template<size_t I> using Iter = decltype(std::get<I>(iterables).begin());
         template<size_t I> using Data = decltype(*std::get<I>(iterables).begin());
         template<typename> struct base_iterator;
 
-        template<std::size_t... Is>
-        struct base_iterator<std::integer_sequence<std::size_t, Is...>> {
-                using value_type = std::tuple< Data<Is>... >;
-                std::tuple<Iter<Is>...> iterators;
-
-                base_iterator( Iter<Is>... is ) : iterators( is... ) {}
+        // This inner template puts the sequence of `0, 1, ... sizeof...(Args)-1`
+        // into a pack. These are the indexes into the tuples, so unpacking can
+        // go over each element of the tuple.
+        // The std::integer_sequence is just used to build that sequence.
+        // A library reference will probably explain it better than I can.
+        template<std::size_t... Indices>
+        struct base_iterator<std::integer_sequence<std::size_t, Indices...>> {
+                using value_type = std::tuple< Data<Indices>... >;
+                std::tuple<Iter<Indices>...> iterators;
+
+                base_iterator( Iter<Indices>... is ) : iterators( is... ) {}
                 base_iterator operator++() {
-                        return base_iterator( ++std::get<Is>( iterators )... );
+                        return base_iterator( ++std::get<Indices>( iterators )... );
                 }
                 bool operator!=( const base_iterator& other ) const {
@@ -478 +484 @@
                 }
                 value_type operator*() const {
-                        return std::tie( *std::get<Is>( iterators )... );
+                        return std::tie( *std::get<Indices>( iterators )... );
                 }
 
                 static base_iterator make_begin( Iterables & data ) {
-                        return base_iterator( std::get<Is>( data ).begin()... );
+                        return base_iterator( std::get<Indices>( data ).begin()... );
                 }
                 static base_iterator make_end( Iterables & data ) {
-                        return base_iterator( std::get<Is>( data ).end()... );
+                        return base_iterator( std::get<Indices>( data ).end()... );
                 }
         };