On Thu, Feb 9, 2012 at 11:23 AM, Ian Lynagh
On Thu, Feb 09, 2012 at 04:52:16AM -0800, John Meacham wrote:
Since CSigSet has "sigset_t" associated with it, 'Ptr CSigSet' ends up turning into 'sigset_t *' in the generated code. (Ptr (Ptr CChar)) turns into char** and so forth.
What does the syntax for associating sigset_t with CSigSet look like?
There currently isn't a user accessable once, but CSigSet is included in the FFI spec so having the complier know about it isn't that bad. In fact, it is how I interpreted the standard. Otherwise, why would CFile be specified if it didn't expand 'Ptr CFile' properly. I just have a single list of associations that is easy to update at the moment, but a user defineable way is something i want in the future. My current syntax idea is. data CFile = foreign "stdio.h FILE" but it doesn't extend easily to 'newtype's or maybe a {-# CTYPE "FILE" #-} pragma... The 'Ptr' trick is useful for more than just pointers, I use the same thing to support native complex numbers. I have data Complex_ :: # -> # -- type function of unboxed types to unboxed types. then can do things like 'Complex_ Float64_' to get hardware supported complex doubles. The expansion happens just like 'Ptr' except instead of postpending '*' when it encounters _Complex, it prepends '_Complex ' (a C99 standard keyword). You can then import primitives like normal (for jhc) foreign import primitive "Add" complexPlus :: Complex_ Float64_ -> Complex_ Float64_ -> Complex_ Float64_ and lift it into a data type and add instances for the standard numeric classes if you wish. (I have macros that automate the somewhat repetitive instance creation in lib/jhc/Jhc/Num.m4) John