### Settable socket option requirements

In the table below, `X` denotes a socket option class, `a` denotes a value of `X`, `p` denotes a value that meets the protocol requirements, and `u` denotes an identifier.

Table 18. SettableSocketOption requirements

expression | type | assertion/note pre/post-conditions
--- | --- | ---
`a.level(p);` | `int` | Returns a value suitable for passing as the level argument to POSIX `setsockopt()` (or equivalent).
`a.name(p);` | `int` | Returns a value suitable for passing as the option_name argument to POSIX `setsockopt()` (or equivalent).
`const X& u = a; u.data(p);` | a pointer, convertible to `const void*` | Returns a pointer suitable for passing as the option_value argument to POSIX `setsockopt()` (or equivalent).
`a.size(p);` | `size_t` | Returns a value suitable for passing as the option_len argument to POSIX `setsockopt()` (or equivalent), after appropriate integer conversion has been performed.