C structs are a bit tricky because different compilers, and different compiler options, can result in different layouts in memory for the structs.
That said, something like this looks like it should be straightforward (I expect that most compilers would not introduce padding between members of the struct). FYI, -- Raul On Tue, Oct 5, 2021 at 1:33 PM 'robert therriault' via General <[email protected]> wrote: > > Alex, > > I haven't done very much of that myself, but have you looked at chapter 21 of > JforC? > https://www.jsoftware.com/help/jforc/calling_external_programs.htm#_Toc191734429 > > Cheers, bob > > > On Oct 5, 2021, at 09:21, Alex Shroyer <[email protected]> wrote: > > > > How do I send/receive data structures to/from C functions using the cd verb? > > > > For example if I have this C library saved as /tmp/example.dylib, how do I > > call it from J? > > > > // C code: > > struct stuff {double a[2]; int i;}; > > void fn(struct stuff *x) {x->a[x->i] += 100;} > > > > NB. J code: > > data =: (2.3 4.5);0 NB. the data I would like to send to fn (array of 2 > > doubles; int) > > '/tmp/example.dylib fn (declaration)' cd (parameters) > > > > Specifically, what do I use for the (declaration) and what do I use for > > (parameters)? > > I presume I should use something from > > https://www.jsoftware.com/help/dictionary/dx003.htm but I'm unsure how to > > then specify it in the (declaration). > > > > Is there a relevant example somewhere? > > > > Thanks, > > Alex > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
