[Rcpp-devel] Dispatching based on SEXPTYPE

[Romain Francois]

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.

There is no other way I know about.

Romain

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