Merge pull request #151 from tcbrindle/pr/fix_150

Reset inner_cur of (multipass) flatten_adaptor when reaching the end
tcbrindle · Jan 17, 2024 · 0304fe6 · 0304fe6
2 parents e942a67 + 1fc9de3
commit 0304fe6
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Showing 3 changed files with 39 additions and 1 deletion.
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -34,6 +34,8 @@ target_compile_options(flux-internal INTERFACE
 
     $<$<CXX_COMPILER_ID:GNU>: -fconcepts-diagnostics-depth=2>
 
+    $<$<CXX_COMPILER_ID:Clang,AppleClang>: -fconstexpr-backtrace-limit=0>
+
     $<$<CXX_COMPILER_ID:MSVC>:
         # Various options for closer standard conformance
         /utf-8 /Zc:__cplusplus /Zc:throwingNew /Zc:inline /Zc:externConstexpr

diff --git a/include/flux/op/flatten.hpp b/include/flux/op/flatten.hpp
@@ -129,7 +129,11 @@ struct flatten_adaptor<Base> : inline_sequence_base<flatten_adaptor<Base>> {
 
         static constexpr auto satisfy(auto& self, cursor_type& cur) -> void
         {
-            while (!flux::is_last(self.base_, cur.outer_cur)) {
+            while (true) {
+                if (flux::is_last(self.base_, cur.outer_cur)) {
+                    cur.inner_cur = cursor_t<InnerSeq>{};
+                    return;
+                }
                 auto&& inner = flux::read_at(self.base_, cur.outer_cur);
                 cur.inner_cur = flux::first(inner);
                 if (!flux::is_last(inner, cur.inner_cur)) {

diff --git a/test/test_flatten.cpp b/test/test_flatten.cpp
@@ -226,10 +226,39 @@ constexpr bool test_flatten_multipass()
     }
 #endif // NO_CONSTEXPR_VECTOR
 
+    // Iterating to the end gives last()
+    {
+        std::array<std::string_view, 3> arr{"a", "b", "c"};
+
+        auto seq = flux::flatten(arr);
+
+        auto cur = seq.first();
+        while (!seq.is_last(cur)) {
+            seq.inc(cur);
+        }
+
+        STATIC_CHECK(cur == seq.last());
+    }
+
     return true;
 }
 static_assert(test_flatten_multipass());
 
+#ifndef NO_CONSTEXPR_VECTOR
+constexpr
+#endif
+bool issue_150()
+{
+    const std::vector<std::string> vec{"a", "b", "c"};
+
+    auto str = flux::ref(vec).flatten().to<std::string>();
+
+    return str == "abc";
+}
+#ifndef NO_CONSTEXPR_VECTOR
+static_assert(issue_150());
+#endif
+
 }
 
 TEST_CASE("flatten")
@@ -239,4 +268,7 @@ TEST_CASE("flatten")
 
     bool mp = test_flatten_multipass();
     REQUIRE(mp);
+
+    bool res = issue_150();
+    REQUIRE(res);
 }