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[Rcpp-devel] strange bool conversion?

3 messages · Daniel Sabanés Bové, Romain Francois

Original
Daniel Sabanés Bové
# 
Hi,

I have just discovered an extremely strange behaviour in conversion of
an R logical to a C++ bool. Consider the minimal example:

--- snip ---

library(Rcpp)
library(inline)

## this compiles and loads fine, but is wrong:
wrong <- cxxfunction(signature(x="list") , '
        List input(x);
        const bool a = input[0];
        return wrap(a);
        ' , plugin = "Rcpp")

wrong(list(TRUE))
wrong(list(FALSE))

## this is correct:
correct <- cxxfunction(signature(x="list") , '
        List input(x);
        const bool a = as<bool>(input[0]);
        return wrap(a);
        ' , plugin = "Rcpp")

correct(list(TRUE))
correct(list(FALSE))

--- snap ----

In Rcpp 0.8.9 wrong(list(FALSE)) == TRUE, which is quite surprising to
the user...
Sorry if this already a known feature, but then I would be curious if
this behaviour is really wished?

Thanks in advance,
best regards

Daniel
Romain Francois
# 
Hi, 

Thanks. This is not a feature. 

I think this is about the const keyword and will attempt to fix it later. 

Romain



Le 13 d?c. 2010 ? 05:30 PM, Daniel Saban?s Bov?<daniel.sabanesbove at ifspm.uzh.ch> a ?crit :
Romain Francois
# 
This is fixed now (rev 2789).

For the curious, it seems that the generic_proxy template made the wrong 
choice between these conversion operators:

operator SEXP() const {
     return get() ;
}
			
template <typename U> operator U() const {
     return ::Rcpp::as<U>(get()) ;
}
			
I resolved this by forcing the conversion to bool with this:

operator bool() const {
     return ::Rcpp::as<bool>(get()) ;
}
	
Thanks again for the report.
		
Romain

Le 13/12/10 17:30, Daniel Saban?s Bov? a ?crit :