New on YouTube: How Jane Street made $5B in India (and what SEBI says it did) - Watch now

⚡ Build the skills to land top-paying quant jobs. Offer ends in 23d 14h 02m 28s23 days 14 hours 2 minutes 28 seconds.

Get quant-ready in 2026

⚡ Build the skills to land top-paying quant jobs. Offer ends in 23d 14h 02m 28s23 days 14 hours 2 minutes 28 seconds.

Value Categories, Move and Perfect Forwarding · 3:29

Forwarding References and Reference Collapsing

Two ampersands don't always mean rvalue reference. On a deduced template parameter written exactly as T&&, they make a forwarding reference that binds to anything. We spot the impostors (vector<T>&&, const T&&, a class template's push_back), ask clang what T becomes for lvalues and rvalues, watch Widget& && collapse to Widget&, and see that auto&& follows the same rules.

You will learn

Tell a forwarding reference (deduced T, exact form T&&) from an rvalue reference
Predict the deduced T for lvalue, const lvalue and rvalue arguments
Apply the reference collapsing rule: any & makes the result &
Explain what auto&& binds to and why forwarding needs this machinery

Chapters

Previousstd::move Moves Nothing Nextmove vs forward, and Return Value Optimization