Explain why a custom allocator is needed at start of the book

Hi, thanks for the book It is very helpful.

I don't get the rationale for having a custom allocator though, shouldn't it be explained at the start? Wouldn't default rust allocator be good for this?

[pliniker]

Yes, thank you, it does seem I need to explain better in the text why I have taken this approach.

An explanation:

• It is entirely valid to take a native rust std approach such as Rc/Arc. Many interpreter projects in Rust have done so.
• The next level of complexity is to use something similar in API to Rc but that handles cycles and has a distinct collection phase, such as https://github.com/Manishearth/rust-gc/
• In both the above situations, the std collections can be used.
• I wanted to demonstrate building allocation, data structures and collection from the ground up so that the interested reader can understand the specific challenges and solutions that are experienced in Rust.
• At the time of writing code, the default rust allocator and APIs were unstable and not yet suitable. The situation now might be different.

thanks for the explanation