docs(tutorial): Clarify examples in chapter 5

src/_tutorial/chapter_5.rs

@@ -136,8 +136,8 @@
 //! # }
 //! ```
 //!
-//! You'll notice that the above allows trailing `,` when we intended to not support that. We can
-//! easily fix this by using [`separated`]:
+//! You'll notice that the above allows trailing `,`. However, if that's not desired, it
+//! can easily be fixed by using [`separated`] instead of [`repeat`]:
 //! ```rust
 //! # use winnow::prelude::*;
 //! # use winnow::token::take_while;
@@ -199,9 +199,23 @@
 //! }
 //! ```
 //!
-//! If you look closely at [`repeat`], it isn't collecting directly into a [`Vec`] but
-//! anything that implements the [`Accumulate`] trait to gather the results. This lets us make more complex parsers than we did in
-//! [`chapter_2`] by accumulating the results into a `()` and [`take`][Parser::take]-ing the captured input:
+//! If you look closely at [`separated`] and [`repeat`], they don't always collect the result into
+//! a [`Vec`], but rather anything that implements the [`Accumulate`] trait.
+//! [`Accumulate`] is for instance also implemented for [`HashSet`], [`String`] and `()`.
+//!
+//! This enables you to build more complex parsers than shown in [`chapter_2`] by accumulating
+//! complex expressions into a single `&str`. This is done by `[`take`][Parser::take]-ing the
+//! `parse_list` parser, which effectively encapsulates it in a [`Take`].
+//!
+//! [`Take`] works by creating a [`checkpoint`][Stream::checkpoint] before running the
+//! inner parser. In our case the `parse_list` parser then advances to the end of the digit list,
+//! afterwards `Take` reads the offset (i.e. how many chars were matched by `parse_list`),
+//! restores the checkpoint, and returns the whole digit list as a single string based on
+//! the previously read offset.
+//!
+//! Due to this `Take` doesn't care about the result of `parse_list`, which is why `parse_list`
+//! simply accumulates into a `()`, which effectively discards the product of `parse_list`.
+//!
 //! ```rust
 //! # use winnow::prelude::*;
 //! # use winnow::token::take_while;
@@ -273,8 +287,11 @@ use super::chapter_3;
 use crate::combinator;
 use crate::combinator::repeat;
 use crate::combinator::separated;
+use crate::combinator::Take;
 use crate::stream::Accumulate;
+use crate::stream::Stream;
 use crate::Parser;
+use std::collections::HashSet;
 use std::vec::Vec;
 
 pub use super::chapter_4 as previous;