[Rcpp-devel] A simple List example that has me stumped

[Dirk Eddelbuettel]

On 17 September 2012 at 15:44, Rodney Sparapani wrote:
| On 09/17/2012 03:02 PM, Dirk Eddelbuettel wrote:
| > You are once again tripping over as<>() and wrap().  You_must_  use as<int>
| > as the following working example:
| 
| Right.  Is there a rule of thumb to determine when we need as<>()?
| I have other examples where it seems to work without it, but I
| can't seem to see a pattern.  Or should you just use it all
| of the time whether it is needed or not?  Thanks!

Heuristically speaking:

  -- always use it for atomistic C/C++ types: int, double, bool, ...

  -- rely on SEXP types to corresponding Rcpp types happening automatically
     due to implicit use of as<>(), particularly vector / matrix types works:
     IntegerVector, NumericMatrix, List, Environment, Function, XPtr, ...

And the same is true for wrap: for sure with int, double, ...; generally not
need for core Rcpp types wrapping a SEXP.

If it fails, the compiler usually tells you.  I have not been bitten by
silent failure like the one you reported.  But then I also do not try to cram
multiple assignments into a single line...

Dirk

-- 
Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com