R folks, I'm curious about possible support for Lisp-style macros in R. I'm aware of the "defmacro" support for S-Plus and R discussed here:
http://www.biostat.wustl.edu/archives/html/s-news/2002-10/msg00064.html but that's really just a syntactic short-cut to the run-time use of substitute() and eval(), which you could manually put into a function yourself if you cared too. (AKA, not at all equivalent to Lisp macros.) The mlocal() function in mvbutils also has seemingly similar macro-using-eval properties: http://cran.r-project.org/src/contrib/Descriptions/mvbutils.html http://www.maths.lth.se/help/R/.R/library/mvbutils/html/mlocal.html I could of course pre-process R source code, either using a custom script or something like M5: http://www.soe.ucsc.edu/~brucem/samples.html http://groups.google.com/group/comp.compilers/browse_thread/thread/8ece2f34620f7957/000475ab31140327 But that's not what I'm asking about here. As I understand it, Lisp-style macros manipulate the already-parsed syntax tree. This seems very uncommon in non-Lisp languages and environments, but some - like Python - do have such support. (I don't use Python, but I'm told that its standard parser APIs are as powerful as Lisp macros, although clunkier to use.) Is implementing Lisp-style macros feasible in R? Has anyone investigated this or tried to do it? What internal representation does R use for its parse tree, and how could I go about manipulating it in some fashion, either at package build time or at run time, in order to support true Lisp-style macros? Whenever I try something like this in R: > dput(parse(text="1+2")) expression(1 + 2) what I see looks exactly like R code - that '1 + 2' expression doesn't look very "parsed" to me. Is that really it, or is there some sort of Scheme-like parse tree hiding underneath? I see that the interactive Read-Eval-Print loop basically calls R_Parse1() in "src/main/gram.c", but from there I'm pretty much lost. Also, what happens at package build time? I know that R CMD INSTALL generates binary *.rdb and *.rdx files for my package, but what do those do exactly, and how do they relate to the REPL and R_Parse1()? Finally, are there any docs describing the design and implementation of the R internals? Should I be looking anywhere other than the R developer page here?: http://developer.r-project.org/ Thanks! -- Andrew Piskorski <[EMAIL PROTECTED]> http://www.piskorski.com/ ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
