From lars at predict.com  Fri Jun 17 18:45:16 2005
From: lars at predict.com (lars@predict.com)
Date: Fri, 17 Jun 2005 18:45:16 +0200 (CEST)
Subject: [Rd] (PR#7951) DispatchOrEval missing in do_isfinite and
	do_isinfinite
Message-ID: <20050617164516.D8830A24A@slim.kubism.ku.dk>

Hi,

OK, if you try to explicitly make them generic, you are told that they 
are implicitly already generic:

 > setGeneric("is.finite", function(from, ...) standardGeneric("is.finite"))
Error in setGeneric("is.finite", function(from, ...) 
standardGeneric("is.finite")) :
    "is.finite" is a primitive function;  methods can be defined, but 
the generic function is implicit, and can't be changed.

If you query about its genericness before you define you own generic, 
you get:

 > isGeneric("is.finite")
[1] FALSE

But after you define you own generic, you get:

 > setMethod("is.finite", signature(x="TS"),
+           function(x) {
+              Data(x) = callNextMethod()
+              x
+           })
[1] "is.finite"

 > isGeneric("is.finite")
[1] TRUE

This all makes some sense, but I am not familiar enough with he 
internals to explain exactly why it is done this way. I think you will 
fine that 'is.nan' behave exactly the same way.

Thanks,
Lars


Prof Brian Ripley wrote:

> These functions are not generic according to the help page.
> The same page says explicitly that is.nan is generic.
>
> Where did you get the (false) idea that they were generic?
>
> On Thu, 16 Jun 2005 lars at predict.com wrote:
>
>> Full_Name: Lars Hansen
>> Version: 2.1.0
>> OS: SunOS 5.8
>> Submission from: (NULL) (207.66.36.189)
>>
>>
>> Hi,
>>
>> S4 method displacth does not work for the two generic functions 
>> 'is.finite' and 'is.infinite'. It turns out that the C functions 
>> 'do_isfinite' and 'do_isinfinite' in src/main/coerce.c are missing a 
>> call to 'DispatchOrEval' (see do_isnan). Added in the call fixed the 
>> problem. My functions no look like this:
>>
>> Form coerce.c:
>>
>> SEXP do_isfinite(SEXP call, SEXP op, SEXP args, SEXP rho)
>> {
>>    SEXP ans, x, names, dims;
>>    int i, n;
>>
>>    if (DispatchOrEval(call, op, "is.finite", args, rho, &ans, 1, 1))
>>        return(ans);
>>
>>    checkArity(op, args);
>>    ...
>>
>> SEXP do_isinfinite(SEXP call, SEXP op, SEXP args, SEXP rho)
>> {
>>    SEXP ans, x, names, dims;
>>    double xr, xi;
>>    int i, n;
>>
>>    if (DispatchOrEval(call, op, "is.infinite", args, rho, &ans, 1, 1))
>>        return(ans);
>>
>>    checkArity(op, args);
>>    ...
>
>



[Rd] (PR#7951) DispatchOrEval missing in do_isfinite and do_isinfinite
lars@predict.com