[R] Integer vs numeric

[cgenolin at u-paris10.fr]

Seems strange to me to define an operator relatively to a very special case.
I have to admit that I do not use 1:1e7 every day :-)

Wouldn't it be more appropriate to define a a:b operator numeric (that 
is preserving the initial class of a and b) and in specific case that 
need optimization, changing the type?

for i in as.integer(1:1e7)

That might appears as a minor point, but when using S4, for what I 
know, if you define a class that can take either 1:3 or c(1,3,4), one 
is integer, the other numeric, one of those will not be accepted by the 
class...

Christophe


> On 28-Jan-08 22:40:02, Peter Dalgaard wrote:
>> [...]
>> AFAIR, space is/was more of an issue. If you do something like
>>
>> for i in 1:1e7
>>     some.silly.simulation()
>>
>> then you have 40 MB sitting there doing nothing, and 80 MB if
>> it had been floating point.
>
> Hmmm ... there's something to be said for good old
>
>  for(i=1,i<=1e7,i++){....}
>
> As pointed out in ?"for", when you do
>
>  for(i in X){...}  #(e.g. X=(1:1e7))
>
> the object X is created (or is already there) in full
> at the start and sits there, as you say doing nothing,
> until you end the loop. Whereas the C code just keeps
> track of i and of the condition.
>
> At least on a couple of my machines (64MB and 184MB RAM)
> knocking out 40MB would inflict severe trauma! Let alone 80MB.
> Mind you, the little one is no longer allowed to play with
> big boys like R, though the other one is still used for
> moderate-sized games.
>
> Would there be much of a time penalty in implementing
> a 'for' loop, C-style, as
>
>  i<-1
>  while(i<=1e7){
>    ...
>    i<-i+1
>  }
>
> ??
>
> It looks as though there might be:
>
>  system.time(for(i in (1:1e7)) x<-cos(3) )
>  #[1] 13.521  0.132 13.355  0.000  0.000
>  system.time({i<-1;while(i<=1e7){x<-cos(3);i<-i+1}})
>  #[1] 38.270  0.076 37.629  0.000  0.000
>
> which suggests that the latter is about 3 times as slow.
> (And no, this wasn't done on either of my puny babes).
>
> (And this isn't the first time I've wished for an R
> implementation of "++" as a CPU-level incrementation,
> as opposed to the R-arithmetic implementation which
> treats "adding 1 to a variable" as a full-dress
> arithmetic parade!
>
> Best wishes,
> Ted.
>
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> E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
> Fax-to-email: +44 (0)870 094 0861
> Date: 28-Jan-08                                       Time: 23:34:52
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