[Rd] advice on F77_SUB and F77_CALL

[jing hua zhao]

Dear colleagues,

I would like to have your advice on how to call C from Fortran. Essentially 
I have a Fortran program for numerical optimisation that often uses object 
function as its function/subrouine arguements. However, it appears most 
examples of F77_SUB concern about arrays/matrices and not function -- I 
could work directly with C with help of f2c but it would be very nice to 
keep the familiar Fortran code intact. I have tried to remove the argument 
and keep it in an Fortran EXTERNAL statement.  The Fortran routine is 
appealing to me as it handles nonlinear constraints.

I tried to work it out like this: use .Call from R to call a C wrapper which 
processes the environment and parses R expressions, use F77_CALL to call the 
Fortran routines which in turn uses an objective function in C -- I use 
global variables to pass the environment and R function from the C wrapper 
to C objective function. I have problem with F77_CALL, however.

This sounds a bit confusing though simple conceptually. I am grateful of any 
example or idea.

Many thanks,


Jing Hua