C++ New Notes

Lambda expressions (since C++11)

Constructs a closure: an unnamed function object capable of capturing variables in scope.
[ captures ] <tparams>(optional)(c++20) ( params ) specifiers(optional) exception attr -> ret { body } (1)
[ captures ] ( params ) -> ret { body } (2)
[ captures ] ( params ) { body } (3)
[ captures ] { body } (4)

Parameter pack
A template parameter pack is a template parameter that accepts zero or more template arguments (non-types, types, or templates). 
A function parameter pack is a function parameter that accepts zero or more function arguments.
A template with at least one parameter pack is called a variadic template.

decltype (declared type)

Inspects the declared type of an entity or the type and value category of an expression.