# Topics Rows are ordered based on estimated difficulty. | lifetimes\[-adjacent\] | `trait`s | `struct`s | |------------------------|--------------------|---------------| | [explicit lifetimes] | [`Fn`?] | [`Duration`] | | [from reference] | [`async` `Fn`] | [All Errors?] | | [extracting lifetimes] | [exclusive traits] | [`RcChars`] | | [composition] | [merging traits] | [`AnyStr`] | p.s. most of the exercises are actually about `trait`s, this categorisation isn't strict. [explicit lifetimes]: ./exercises/refbind.md [`Fn`?]: ./exercises/bind.md [`RcChars`]: ./exercises/rcchars.md [extracting lifetimes]: ./exercises/bool_stream.md [exclusive traits]: ./exercises/multiple_blanket.md [merging traits]: ./exercises/modes.md [`AnyStr`]: ./exercises/anystr.md [composition]: ./exercises/composition.md [`Duration`]: ./exercises/duration.md [All Errors?]: ./exercises/all_errors.md [from reference]: ./exercises/fromref.md [`async` `Fn`]: ./exercises/async_fn.md