On 4/8/2008 7:42 AM, Gabor Grothendieck wrote:
> I think what he is referring to is that findGlobals lists mean under
> variables rather than functions when you do this with his f:
>
>> findGlobals(f, FALSE)
> $functions
> [1] "{" "apply"
>
> $variables
> [1] "mean"
Yes, I understood that, and I think it's reasonable behaviour.
findGlobals analyzes the syntax, not the semantics.
Duncan Murdoch
>
> On Tue, Apr 8, 2008 at 7:14 AM, Duncan Murdoch <[EMAIL PROTECTED]> wrote:
>> Christophe Genolini wrote:
>> >>> f <- function(x){apply(x,2,mean)}
>> >>> findGlobals(f)
>> >>>
>> >> mean is a global variable, so findGlobals gets it right.
>> >>
>> > That sound strange to me: a "variable" is something that vary... mean
>> > does not vary. maen will ge an argument that is a line of x and will
>> > make some calculous on it, that is the comportement of a function.
>> > Of course, mean is an argument of an other function, but I do not think
>> > this is a reason good enouth to say that mean is a variable.
>> >
>>
>> findGlobals doesn't try to tell what mean is; it's just reporting on how
>> you've used it. Your usage means that the interpreter will treat it as
>> a variable, getting a copy of its value and passing it as an argument to
>> apply. (That's an oversimplification, of course: it's very unlikely
>> that an actual copy will be made, but it will act as if one was made.)
>>
>> > Furthemore, I use findGlobals to detect some typo. In
>> >
>> > f <- function(myObject){return(mObject^2)}
>> >
>> > findGlobals will detect that mObject is a global so I know there is a
>> > typo somewhere.
>> > Considering mean as a globals do not let us use findGlobals this way.
>> >
>> >
>>
>> You can still use it to detect that kind of typo, but you need a second
>> step where you check whether the globals exist in the environment of the
>> function or not. That test won't be perfect either: it will miss cases
>> where you meant to type a local variable, but by mistake typed the name
>> of some global. Most uses of mean as a variable would fall into that
>> category; unfortunately (?) apply means some of them are legitimate.
>>
>> I think the best you'll ever be able to do is to get some suggestions of
>> errors, with both false positives and false negatives. If there were
>> cases where some usage was definitely an error, the parser would
>> probably catch it.
>>
>> Duncan Murdoch
>>
>>
>>
>> > Christophe
>> >
>> > ______________________________________________
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>> >
>>
>> ______________________________________________
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>>
>
> ______________________________________________
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