Function .C — argument setup fails compilation

Question

I\'m currently learning to call compiled C code in R. Yesterday I created a function for the infinite pi series that when run in R returns a length 1 numeric vector (pi), w

Answer 1

You could load Rcpp just to get access to its Rcpp Attributes functionality. It permits you to write this as (expanded to two lines for display; it really fits on one line):

R> cppFunction('double fib(double n) { if (n<2) return(n); 
+                                      else return fib(n-1) + fib(n-2);}')
R> fib(10)
[1] 55
R> 

If you run cppFunction(..., verbose=TRUE) you get to see the file it creates.

In general, avoid the .C() interface and concentrate in .Call(). This is the very clear recommendation in the NEWS file of the most recent R release:

* .C(DUP = FALSE) and .Fortran(DUP = FALSE) are now deprecated, and
  may be disabled in future versions of R.  As their help has long
  said, .Call() is much preferred.

Let's stress the .Call() is much preferred one more time. See eg Hadley's Advanced R Programming draft for more on getting going with .Call(). His advice too is to straight to Rcpp.