Changeset 63be3387 for src/Common/utility.h

Timestamp:

Nov 14, 2022, 11:52:44 AM (3 years ago)

Author:

caparson <caparson@…>

Branches:

ADT, ast-experimental, master

Children:

7d9598d8

Parents:

b77f0e1 (diff), 19a8c40 (diff)
Note: this is a merge changeset, the changes displayed below correspond to the merge itself.
Use the (diff) links above to see all the changes relative to each parent.

Message:

Merge branch 'master' of plg.uwaterloo.ca:software/cfa/cfa-cc

File:

• src/Common/utility.h (modified) (1 diff)

src/Common/utility.h

@@ -452 +452 @@
 
 // -----------------------------------------------------------------------------
-// Helper struct and function to support
-// for ( val : group_iterate( container1, container2, ... ) ) {}
-// syntax to have a for each that iterates multiple containers of the same length
-// TODO: update to use variadic arguments
-
-template< typename T1, typename T2 >
-struct group_iterate_t {
-private:
-        std::tuple<T1, T2> args;
+// Helper struct and function to support:
+// for ( auto val : group_iterate( container1, container2, ... ) ) { ... }
+// This iteraters through multiple containers of the same size.
+
+template<typename... Args>
+class group_iterate_t {
+        using Iterables = std::tuple<Args...>;
+        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;
+
+        // 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<Indices>( iterators )... );
+                }
+                bool operator!=( const base_iterator& other ) const {
+                        return iterators != other.iterators;
+                }
+                value_type operator*() const {
+                        return std::tie( *std::get<Indices>( iterators )... );
+                }
+
+                static base_iterator make_begin( Iterables & data ) {
+                        return base_iterator( std::get<Indices>( data ).begin()... );
+                }
+                static base_iterator make_end( Iterables & data ) {
+                        return base_iterator( std::get<Indices>( data ).end()... );
+                }
+        };
+
 public:
-        group_iterate_t( bool skipBoundsCheck, const T1 & v1, const T2 & v2 ) : args(v1, v2) {
-                assertf(skipBoundsCheck || v1.size() == v2.size(), "group iteration requires containers of the same size: <%zd, %zd>.", v1.size(), v2.size());
-        };
-
-        typedef std::tuple<decltype(*std::get<0>(args).begin()), decltype(*std::get<1>(args).begin())> value_type;
-        typedef decltype(std::get<0>(args).begin()) T1Iter;
-        typedef decltype(std::get<1>(args).begin()) T2Iter;
-
-        struct iterator {
-                typedef std::tuple<T1Iter, T2Iter> IterTuple;
-                IterTuple it;
-                iterator( T1Iter i1, T2Iter i2 ) : it( i1, i2 ) {}
-                iterator operator++() {
-                        return iterator( ++std::get<0>(it), ++std::get<1>(it) );
-                }
-                bool operator!=( const iterator &other ) const { return it != other.it; }
-                value_type operator*() const { return std::tie( *std::get<0>(it), *std::get<1>(it) ); }
-        };
-
-        iterator begin() { return iterator( std::get<0>(args).begin(), std::get<1>(args).begin() ); }
-        iterator end() { return iterator( std::get<0>(args).end(), std::get<1>(args).end() ); }
-};
-
-/// performs bounds check to ensure that all arguments are of the same length.
+        group_iterate_t( const Args &... args ) : iterables( args... ) {}
+
+        using iterator = base_iterator<decltype(
+                std::make_integer_sequence<std::size_t, sizeof...(Args)>())>;
+
+        iterator begin() { return iterator::make_begin( iterables ); }
+        iterator end() { return iterator::make_end( iterables ); }
+};
+
+// Helpers for the bounds checks (the non-varatic part of group_iterate):
+static inline void runGroupBoundsCheck(size_t size0, size_t size1) {
+        assertf( size0 == size1,
+                "group iteration requires containers of the same size: <%zd, %zd>.",
+                size0, size1 );
+}
+
+static inline void runGroupBoundsCheck(size_t size0, size_t size1, size_t size2) {
+        assertf( size0 == size1 && size1 == size2,
+                "group iteration requires containers of the same size: <%zd, %zd, %zd>.",
+                size0, size1, size2 );
+}
+
+/// Performs bounds check to ensure that all arguments are of the same length.
 template< typename... Args >
 group_iterate_t<Args...> group_iterate( Args &&... args ) {
-        return group_iterate_t<Args...>(false, std::forward<Args>( args )...);
-}
-
-/// does not perform a bounds check - requires user to ensure that iteration terminates when appropriate.
+        runGroupBoundsCheck( args.size()... );
+        return group_iterate_t<Args...>( std::forward<Args>( args )... );
+}
+
+/// Does not perform a bounds check - requires user to ensure that iteration terminates when appropriate.
 template< typename... Args >
 group_iterate_t<Args...> unsafe_group_iterate( Args &&... args ) {
-        return group_iterate_t<Args...>(true, std::forward<Args>( args )...);
+        return group_iterate_t<Args...>( std::forward<Args>( args )... );
 }