[Ecls-list] Accessing cons values in C
Hi, I’ve spent a good while looking through the project’s documentation (and finding useful apparently undocumented functions such as `ecl_base_string_pointer_safe`) but I cannot for the life of me work out how to access the values of a list stored in cons cells. If I have a function that calls back into C with an argument passed as such: (foo ‘(1 2 3)) what’s the best way to access the values of the cells in that list? The best I’ve found so far is either using cl_nth or cl_cdr and friends and then converting to a C number type, this seems a bit silly when I can access the value of a string by following the pointer tree. The documentation points to a type t_cons in the enum for ecl_t_of, but I can’t find it, or the cons value in the lispunion. Am I missing something obvious here or do I just have to use the cl functions in C to access elements of what is essentially lisp’s simplest data type? Cheers, Chris -- ___ Ecls-list mailing list Ecls-list@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/ecls-list
Re: [Ecls-list] Accessing cons values in C
Chris Osborne writes: > Am I missing something obvious here or do I just have to use the cl > functions in C to access elements of what is essentially lisp’s > simplest data type? You wouldn't want random C code to fuck with your data structures, would you? Don't write C code! -- __Pascal Bourguignon__ http://www.informatimago.com/ “The factory of the future will have only two employees, a man and a dog. The man will be there to feed the dog. The dog will be there to keep the man from touching the equipment.” -- Carl Bass CEO Autodesk -- ___ Ecls-list mailing list Ecls-list@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/ecls-list
Re: [Ecls-list] Accessing cons values in C
Well, I can understand the sentiment, but whilst I said C, it’s actually modern C++ which is approaching lisp with every new standard IMO. I’m using ECL in an *extremely* overkill capacity to to act as “smart” config files and to run a simple REPL for the user to play around with configuring the application’s output how they want (rather than being yet another application that defines a new language lacking in logic for its interactive interface), thus all major computations are passed back to C++, so I’d rather be able to rapidly traverse the trees to extract the commands input by the user. Anyhow, here’s the solution: I just found that enable-smallcons is on by default (for some major performance gains when I looked into it). In this scenario, there’s a set of macros ECL_CONS_PTR, ECL_CONS_CAR etc. defined in object.h to access the cons pointers directly, not sure how I missed this earlier, but at least I’ve found it now (hopefully the info will also show up in the mailing list archive in a web search if anyone else needs it). Cheers! > On 30 Jul 2015, at 00:11, Pascal J. Bourguignon > wrote: > > Chris Osborne writes: > >> Am I missing something obvious here or do I just have to use the cl >> functions in C to access elements of what is essentially lisp’s >> simplest data type? > > You wouldn't want random C code to fuck with your data structures, would > you? > > Don't write C code! > > -- > __Pascal Bourguignon__ http://www.informatimago.com/ > “The factory of the future will have only two employees, a man and a > dog. The man will be there to feed the dog. The dog will be there to > keep the man from touching the equipment.” -- Carl Bass CEO Autodesk > > > -- > ___ > Ecls-list mailing list > Ecls-list@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/ecls-list -- ___ Ecls-list mailing list Ecls-list@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/ecls-list
Re: [Ecls-list] Accessing cons values in C
On Thu, 30 Jul 2015, Chris Osborne wrote: Anyhow, here’s the solution: I just found that enable-smallcons is on by default (for some major performance gains when I looked into it). In this scenario, there’s a set of macros ECL_CONS_PTR, ECL_CONS_CAR etc. defined in object.h to access the cons pointers directly, not sure how I missed this earlier, but at least I’ve found it now (hopefully the info will also show up in the mailing list archive in a web search if anyone else needs it). I think the recommended interface lives in cons.h, where CAR and CDR are defined as macros that, if ECL_CAN_INLINE is true, resolve to essentially inlined functions that call the macros ECL_CONS_CAR and ECL_CONS_CDR. The only thing they do extra is test if the argument is NIL and do the appropriate thing in those cases (where ECL_CONS_* would probably fail). You might want to check if for your application the tiny overhead of checking for NIL is so troublesome that you're willing to sacrifice robustness against NIL arguments and readability (it doesn't get much better than CAR and CDR for asking of the car and the cdr of a cons) Kind regards, Nils-- ___ Ecls-list mailing list Ecls-list@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/ecls-list
