Add summary and explanation of P1789

content/expansion-statements-library-support.md

@@ -0,0 +1,40 @@
+---
+execute: true
+---
+
+## What It Does
+
+`std::integer_sequence` can now be used in `template for`
+to conveniently write a loop where the loop index is a `constexpr` variable,
+as well as to create a `constexpr` pack using structured bindings.
+This is made possible by specializing `std::tuple_size`, `std::tuple_element`, and `std::get`
+for `std::integer_sequence`.
+
+## Why It Matters
+
+These changes remove boilerplate code such as creating an immediately invoked lambda expression
+when creating a `constexpr` pack of indices or writing a loop with a `constexpr` index.
+This is especially important because C++26 supports pack indexing,
+where a `constexpr` index is needed.
+
+## Example
+
+```cpp
+#include <utility>
+#include <tuple>
+#include <print>
+
+int main() {
+    auto tup = std::tuple{1, 3.14, "hello"};
+
+    // Output:
+    //   tup[0] = 1
+    //   tup[1] = 3.14
+    //   tup[2] = hello
+    template for (constexpr std::size_t I : std::make_index_sequence<3>()) {
+        std::println("tup[{}] = {}", I, std::get<I>(tup));
+    }
+
+    constexpr auto [...Is] = std::make_index_sequence<3>();
+}
+```

features_cpp26.yaml

@@ -1602,6 +1602,8 @@ features:
 
   - desc: "Library Support for Expansion Statements"
     paper: P1789
+    summary: "Specializes `std::tuple_size`, `std::tuple_element`, and `std::get` for `std::integer_sequence` to make it usable in expansion statements and structured bindings."
+    content: expansion-statements-library-support.md
     lib: true
     support: [Clang 22]
     ftm: