Tutorial by Topics: guidelines

This meta post is similar to the python version http://stackoverflow.com/documentation/python/394/meta-documentation-guidelines#t=201607240058406359521. Please make edit suggestions, and comment on those (in lieu of proper comments), so we can flesh out/iterate on these suggestions :)

This is an extension of Python's "Meta: Documentation Guidelines" for Django. These are just proposals, not recommendations. Feel free to edit anything here if you disagree or have something else to mention.

To discuss editing the R tag Docs, visit the R chat.

Explain why certain things are marked unsafe in Rust, and why we might need to use this escape hatch in certain (rare) situations.