Dmitry Bogatov <kact...@gnu.org> writes: > Hello. > > How stable the fact, that > (equal? #'(foo bar) (list #'foo #'bar)) > ?
Not stable. A syntax object for a list can also wrap the whole list, it is not necessarily a list of syntax objects. E.g. the following is a valid syntax object representing '(+ 1 2)': #(syntax-object (+ 1 2) ((top)) (hygiene guile-user)) > Why? Combining two syntax objects in list can be done via > #` and #, but it would be nice to know, than I am free > to use all power of list functions. A syntax object like the above example for '(+ 1 2)' could contain source-location or other meta-data. If we guarantee that all non-atomic syntax objects are lists, we lose that ability. It's better that they are "opaque" and that 'syntax-case' or other special operators are the only way to "destructure" them. > Also, it seems there is no syntax-object? predicate. Is it by design? Guile uses psyntax, so syntax objects are actually just vectors! :) You can enter the following in the Guile REPL and see what happens: #(syntax-object (+ 1 2) ((top)) (hygiene guile-user)) Note that it's not the same as: '#(syntax-object (+ 1 2) ((top)) (hygiene guile-user)) (This one is quoted, so it's just a literal vector.) > It seems, than syntax->datum is no-op on non-syntax objects. > Can I rely on it? I think that's also an implementation detail of psyntax. I wouldn't rely on it, but I'm not sure on this one. > Thanks in advance. Happy to help! > -- > Best regards, Dmitry Bogatov <kact...@gnu.org>, > Free Software supporter, esperantisto and netiquette guardian. > git://kaction.name/rc-files.git > GPG: 54B7F00D Taylan
