It is the Rust Playground, not the Playpen

[shepmaster]

"Playpen" was a very old name for it.

[pavelrappo]

It would definitely help if someone could describe the relationship between playground and playpen. When reading mdBook documentation it's not clear what the difference is between {{#playpen}} and fenced runnable code blocks. Both these types seem to be compiled and executed the same way by the Rust Playground.

[ehuss]

playpen is just an old name for playground, they are one in the same.

{{#playpen file.rs}} is identical to:

    ```rust
    {{#include file.rs}}
    ```

It looks like {{#playpen}} predates {{#include}}. Probably not a super-strong reason to have both.

[pavelrappo]

I do like it as a metaphor, though. Kids go outside of their house to get to a playground. Toddlers stay inside and play in a playpen.

mdBook sends the snippets for compilation and execution, receives the results, and shows them in-place. Whereas rustdoc opens a new tab with your code copied to the playground.

Hope that makes sense.

[shepmaster]

My original idea when opening this issue is that anything public-facing in mdBook be updated to use the term "playground". This probably would have backwards-compatibility effects, so I'd expect that playpen in code would stay around as aliases to the newly-renamed thing. Thus #playpen and #playground would do the same, but in all the docs it would only say "playground".

It's a low-priority change, but one that might be more valuable before more people are introduced to mdBook.

[pavelrappo]

Right. Being consistent and expanding vocabulary only if absolutely necessary are good goals. Rustdoc seems to be using the word "playground", so one more reason for mdBook to use that instead of "playpen".