Recall the `static_cast`{.cpp} syntax: `static_cast < @_type-id_@ > ( @_expression_@ )`{.cpp}.

``` template <@[`invocable`]{.rm}[`class`]{.add}@ F@[`, class`]{.add}@> struct @_as-receiver_@ { @[`private:`]{.rm}@  @[`using invocable_type = std::remove_cvref_t<F>;`]{.rm}@  @[`invocable_type`]{.rm}[`F`]{.add}@ f_; @[`public:`]{.rm}@  @@[`explicit @_as-receiver_@(invocable_type&& f)`]{.rm}@@  @@[`@_as-receiver_@(@_as-receiver_@&& other) = default;`]{.rm}@@  void set_value() @[`noexcept(is_nothrow_invocable_v<F&>)`]{.add}@ {  invoke(f_);  }  @[`[[noreturn]]`]{.add}@ void set_error(std::exception_ptr) @[`noexcept`]{.add}@ {  terminate();  }  void set_done() noexcept {} }; ```

::: cmptable ### Before ```cpp switch (x) { case 0: std::cout << "got zero"; break; case 1: std::cout << "got one"; break; default: std::cout << "don't care"; } ``` ### After ```cpp inspect (x) { 0: std::cout << "got zero"; 1: std::cout << "got one"; _: std::cout << "don't care"; } ```  :::

::: cmptable ### Before ```cpp switch (x) { case 0: std::cout << "got zero"; break; case 1: std::cout << "got one"; break; default: std::cout << "don't care"; } ``` ### After ```cpp inspect (x) { 0: std::cout << "got zero"; 1: std::cout << "got one"; _: std::cout << "don't care"; } ```  ---  ```cpp if (s == "foo") {  std::cout << "got foo"; } else if (s == "bar") {  std::cout << "got bar"; } else {  std::cout << "don't care"; } ``` ```cpp inspect (s) { "foo": std::cout << "got foo"; "bar": std::cout << "got bar"; _: std::cout << "don't care"; } ```  :::

::: cmptable > Put your caption here  ### Before ```cpp switch (x) { case 0: std::cout << "got zero"; break; case 1: std::cout << "got one"; break; default: std::cout << "don't care"; } ``` ### After ```cpp inspect (x) { 0: std::cout << "got zero"; 1: std::cout << "got one"; _: std::cout << "don't care"; } ```  :::

```plantuml title Omits Connect & Start caption sequence diagram for set_next() autonumber hide footbox participant consumer as cnm participant producer as pdc participant transformer as trn activate cnm group connect/start sequence activate trn activate pdc end loop values 0..N pdc --> trn : processValN = set_next(produceValN) activate pdc activate trn trn --> cnm : consumeValN = set_next(transformValN) activate cnm group connect/start valueN end pdc --> trn : set_value(transformValNRcvr, ValN...) trn --> cnm : set_value(consumeValNRcvr, transformValN...) cnm --> pdc : set_value(produceValN+1Rcvr) deactivate pdc deactivate trn deactivate cnm end group end sequence pdc --> trn : set_value(transformRcvr) trn --> cnm : set_value(consumeRcvr) deactivate pdc deactivate trn end deactivate cnm ```

[2]{.pnum} An expression is _potentially evaluated_ unless it is an unevaluated operand (7.2) or a subexpression thereof. The set of _potential results_ of an expression `e` is defined as follows: - [2.1]{.pnum} If `e` is an _id-expression_ (7.5.4), the set contains only `e`. - [2.2]{.pnum} If `e` is a subscripting operation (7.6.1.1) with an array operand, the set contains the potential results of that operand.

> | _selection-statement:_ > | `if constexpr`_~opt~_ `(` _init-statement~opt~_ _condition_ `)` _statement_ > | `if constexpr`_~opt~_ `(` _init-statement~opt~_ _condition_ `)` _statement_ `else` _statement_ > | `switch (` _init-statement~opt~_ _condition_ `)` _statement_ > | [`inspect` `constexpr`~_opt_~ `(` _init-statement~opt~_ _condition_ `)` `{` >  _inspect-case-seq_ >  `}`]{.add} > > ::: add > | _inspect-case-seq:_ > | _inspect-case_ > | _inspect-case-seq_ _inspect-case_ > > | _inspect-case:_ > | _attribute-specifier-seq~opt~_ _inspect-pattern_ _inspect-guard~opt~_ `:` _statement_ > > | _inspect-pattern:_ > | _wildcard-pattern_ > | _identifier-pattern_ > | _constant-pattern_ > | _structured-binding-pattern_ > | _alternative-pattern_ > | _binding-pattern_ > | _extractor-pattern_ > > | _inspect-guard:_ > | `if (` _expression_ `)` > :::

In [expr.sizeof]{.sref}/5: The identifier in a `sizeof...` expression shall name a [parameter]{.rm} pack. The `sizeof...` operator yields the number of [arguments provided for]{.rm} [elements in]{.add} the [parameter]{.rm} pack [identifier]{.rm} ([temp.variadic]{.sref}).