C++17

Frequently

• Structured bindings
• if constexpr
• Mandatory Copy Elision or Passing Unmaterialized Objects
• Inline variables
• Nested namespaces
• [[nodiscard]], [[maybe_unused]], [[fallthrough]] attributes
• Template argument deduction for class templates
• Lambda capture this by value
• std::optional
• std::variant
• std::string_view
• std::filesystem
• std::clamp

Moderate

• constexpr lambda
• Selection statements with initializer (if and switch with initialization)
• Aggregate Extensions
• UTF-8 character literals
• Direct-list-initialization of enums
• __has_include
• std::any
• std::invoke
• std::apply
• std::reduce
• std::sample
• std::not_fn
• std::to_chars() and std::from_chars()
• gcd, lcm

Rare

• Declaring non-type template parameters with auto
• Folding expressions
• New rules for auto deduction from braced-init-list
• Class template argument deduction
• std::byte
• Parallel algorithms
• Splicing for maps and sets
• Prefix sum algorithms
• Rounding functions for chrono durations and timepoints