Le 18/04/2018 à 16:15, Jeff Newmiller a écrit :
Regarding:
"Actually, when NULL is provided to where a vector or a matrix is expected just an
error is thrown. So we can hardly imagine that someone would have his program broken or
will be misled if such coercion is introduced."
If all programs were perfect this would be true, but the ability to identify
incorrect pointer initialization is an important feature for testing.
In the late '90s, some Internet Service Providers tried to "assist" users who typed bad
site names into browsers by making failed DNS lookups redirect to a server prepared to supply an
informative "were you looking for X?" web page. This caused significant disruption in
non-user-interactive network protocols that relied on getting a failure notice for bad DNS lookups,
and that idea had to go to the trash heap eventually.
Interesting example but not really "parallel" to our situation.
In R, we already have as.numeric(NULL) without such kind of catastrophe.
I just propose an equivalent functioning in Rcpp.
I don't have failed code tests to offer for this, but the idea of silently
replacing a C++ NULL with a valid value is anathema.
It's not C++ NULL which is coerced (not "replaced") to a vector but R's one.
And only where a vector of a given type is expected, not everywhere.
I think there is a possible compromise.
We can introduce an automatic coercion in #ifdef'ed blocks with e.g.
RCPP_COERCE_NULL_TO_VECTOR and RCPP_COERCE_VECTOR_TO_MARIX optional macros.
In such a way, those who want this feature can have it by defining these macros before including Rcpp.h and those who consider it as anathema can go a
traditional way of doing.
Serguei.
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