Currently, the line-based
# includes that are not line initial are not portable across RStan, PyStan, and CmdStan (which means it only works in RStan and PyStan).
Allowing initial space before
# comments would be a trivial grammar fix (plus some testing).
I strongly prefer the
# to be initial so that it is easy to scan a file for includes. The main purpose of syntactic conventions, in my opinion, is to make files easy to scan, not to make them look pretty.
# comments get deprecated, the current indented syntax is especially easy to confuse with comments; this will improve with Stan 3 when the
# comments will be disallowed (they’re already deprecated, so I’m wondering if the interfaces are getting deprecation warnings with their includes).
But I prefer consistency and if this is something that the interface devs feel they need to hack around to create a non-standard language, I guess I don’t feel that strongly about it.
Other opinions here? We may have even decided something about this at some point, but we don’t have any running record of decisions anywhere.