On 22 November 2012 at 16:42, Romain Francois wrote:
| Le 22/11/12 16:25, Hadley Wickham a écrit :
| >> #define DISPATCH_METHOD(method, x) \
| >> switch( TYPEOF(x) ){ \
| >> case REALSXP: \
| >> return method<REALSXP>(x); \
| >> case INTSXP: \
| >> return method<INTSXP>(x); \
| >> case STRSXP: \
| >> return method<STRSXP>(x); \
| >> case LGLSXP: \
| >> return method<LGLSXP>(x); \
| >> default: \
| >> Rf_error("Unsupported type"); \
| >> return x; \
| >> }
| >
| > Why do we need a macro here? Is it not possible to pass in method as a
| > function? It seems like there must be a more elegant way to do
| > dynamic dispatch.
| >
| > Hadley
|
| Unfortunately, there is not. The issue is that we don't know the type of
| x at compile type, so we have to do this switch dance and trigger
| explicit instanciations of all method<> overloads.
It's one of those times were we get reminded that using C has limitations.
To the compiler SEXP is just one type, and the dispathing on the 'union type'
is done at run-time, not compile time as one could via templates.
| There is no other way I know about.
Switch to Andrew Runnall's CXXR :)
Dirk
--
Dirk Eddelbuettel | e...@debian.org | http://dirk.eddelbuettel.com
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