On Tue, Mar 18, 2014 at 8:54 PM, Paul Tarvydas <paultarvy...@gmail.com>wrote:
> @All, thanks for the interesting discussion. Certainly gives me something > to chew on. > > Re-reading the responses, I see that, while I did sort-of say it, I didn't > emphasize the point of this: > > I have a PEG-syntax parser written in esrap. > > I am binding at least two such parsers as reader-macros (not the normal > kind of macro). > I always thought that reader macros should be called a different name, because they are not macros. Yes, they produce code; but that's the only point they have in common with macros. The two should not be confused. > The first parser parses PEG syntax and creates an esrap program. > > That esrap program, bound as a reader-macro, reads Prolog syntax and > returns a bunch of lisp forms to the reader. > > I have a file of code that contains both, lisp and Prolog syntax > (cl-heredoc to switch between the syntaxes), e.g. > > https://github.com/guitarvydas/paraphrase/blob/master/prolog.lisp > > The parsers read characters, not forms. > > (lisp) > #{ prolog(A,B,c) :- p1(A), p2(B,c). } > (morelisp) > > I am making at least 2 assumptions: > > 1. That using different name spaces for the various parsers will help me > preserve my sanity, (regression testing the PEG parser using itself brings > me to the limits of my comprehension :-), > > 2. That a reader macro must return a single form. I actually want to > return a separate 'defun' for every prolog rule in the file. (Writing this, > just now, makes me ask myself why I don't just put #{ ... } around every > separate rule...) > > (I even started fooling around with a Python syntax). > > This line of thinking was inspired by the Gambit Scheme talk at ILC2010, > where they showed inline infix mathematical expressions. > > Thanks for your suggestions. > Your assumptions are sane. You only have to understand in which phase - read-time, compile-time, run-time - each piece of your code happens to run. Your reader macros generate Lisp code (defun forms), right? Where do the symbols that constitute those forms come from? Let me guess... I bet some come from the source code of the reader macro itself - e.g., the symbol CL:DEFUN. I bet others come from calls you make to the function intern or find-symbol. Am I right? If so, ask yourself: which package is effective at the time you call intern/find-symbol? Can you change it to another one? What happens if you do so?
