a version of source() which keeps comments ?
Martin Maechler <maechler@stat.math.ethz.ch> writes:
I'd like to have this to be used in, e.g., demo() and example(). Currently, source() parse()s the entire file and then evaluates expression by expression. ``Of course'', parse() already loses the comments. An (much slower) alternative might be to the readLine() the file, echo what we read, and try to parse() ``the current chunk''. when parse() fails (when the current expression is incomplete), we silently read the next line, etc, until the expression is complete and hence parse() succeeds, then we eval() and print(). What do people think? Would there be volunteers to write this? [I think it should finalize as an optional argument to source(), but for experimentation it might be easier to try with a function sourceLinewise(.) ].
Historically, this is what source() should have done all the time if it were to be in keeping with other Unix programs (shift input from stdin temporarily). The source() that we have is really "evaluate file". I don't think we can source() an infinite stream like a pipe or a socket, can we? Actually, I think it can be done with a little careful file descriptor switching. (Turn of readline processing, etc., switch stdin to file, run till eof or error, switch back and reestablish readline.) We'd still have the reparse-on-incomplete thing, since that also happens on stdin -- something I suspect isn't necessary, but it takes a fairly hard look at the grammar itself to find out. (This kind of stuff has long been on my might-do list of projects, along with (re)fixing the comment issue and providing better information on parse/eval errors. I'd better not feel possessive about the ideas...)
O__ ---- Peter Dalgaard Blegdamsvej 3 c/ /'_ --- Dept. of Biostatistics 2200 Cph. N (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk) FAX: (+45) 35327907 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-devel-request@stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._