tried it in a couple of syntax-case-enabled schemes (defmacro is implemented using syntax-case in guile) and it doesn't work anywhere. The procedure ends up undefined everywhere.
The #<procedure> object ,inner points to doesn't exist at runtime because it is not defined anywhere in any meaningful way to the compiler. One work-around would be to output the literal lambda in place of ,inner but by then you should just output a (let ...) With the lambda in it and let the inliner take care of it. -- Linus Björnstam On Sat, 1 Feb 2020, at 15:23, David Kastrup wrote: > Linus Björnstam <linus.bjorns...@veryfast.biz> writes: > > > On Sat, 1 Feb 2020, at 12:09, David Kastrup wrote: > >> > >> Can you expand about the "expansion time and macro time separation"? > >> > >> If we have > >> > >> (define decl '()) > >> (define (make-var n v) (list "var" n v)) > >> (defmacro define-session (name value) > >> (define (inner n v) > >> (set! decl > >> (cons > >> (make-var n v) > >> decl)) > >> ) > >> `(,inner ',name ,value)) > >> (define-session foo 1) > >> (display decl) > >> (newline) > >> > >> as stated, the local function "inner" is defined at macro time, but the > >> form > >> `(,inner ',name ,value) > >> does not export the _name_ inner but rather the defined function. That > >> part naively appears to me like it should work; an "expansion time and > >> macro time" issue appears rather to be that inner calls make-var (and > >> accesses decl) which is only being defined at expansion time. > >> > >> The error message, however, rather appears to complain about inner being > >> undefined rather than the definition of inner referring to undefined > >> entities. > > > > > > I am not sure what is really the problem. Either the inner function is > > not present at runtime due to separation of compile time and runtime, > > or it is a result of how defmacro re-introduces the result of the > > macro into the syntactic context of the macro usage (where inner is > > not visible). Either way, having the inner definition in the macro > > output will solve the problem of it not being visible. > > This fails when byte-compiling, so it would appear that the equivalent > of > > (defmacro ... > (define local-fun ... > `(,local-fun ...))) > > is not able to represent the local (and thus ultimately anonymous) > function here. Whether this is a general shortcoming or is conditioned > on local-fun calling functions not available at byte-compile time (in > which case those would need to get wrapped in eval-and-expand) I haven't > checked yet. > > -- > David Kastrup >
