On May 14, 2010, at 3:38 PM, thmsfuller...@gmail.com wrote:
> Hello All,
>
> I tried the sample code from the help. Although '{' is assigned to
> 'do', the call syntaxes for 'do' and '{' are not the same ('do' has
> ','s, but '{' has line breaks). I guess there is a difference in
> parsing the code block of 'do' and the code block of '{'. Could you
> please let me know some internal details so that I can understand the
> differences?
>
{ foo; bar }
gets parsed into
`{`(foo, bar)
as you illustrated below. You can see that in the resulting expression:
> e=parse(text="{foo; bar}")[[1]]
> attributes(e)=NULL ## remove the original sources
> e
{
foo
bar
}
> .Internal(inspect(e))
@102182578 06 LANGSXP g0c0 [NAM(2)]
@10082c9b8 01 SYMSXP g0c0 [MARK,gp=0x4000] "{"
@100edfaa0 01 SYMSXP g0c0 [] "foo"
@100edfc98 01 SYMSXP g0c0 [] "bar"
and in case you are not familiar with the internal representation:
> quote(`{`(foo,bar))
{
foo
bar
}
> .Internal(inspect(quote(`{`(foo,bar))))
@100f99868 06 LANGSXP g0c0 []
@10082c9b8 01 SYMSXP g0c0 [MARK,gp=0x4000] "{"
@100edfaa0 01 SYMSXP g0c0 [] "foo"
@100edfc98 01 SYMSXP g0c0 [] "bar"
Cheers,
Simon
>> do=get("{")
>> do(x <- 3, y <- 2*x-3, 6-x-y)
> [1] 0
>> {
> + x <- 3
> + y <- 2*x-3
> + 6-x-y
> + }
> [1] 0
>> x
> [1] 3
>> y
> [1] 3
>>
>
> --
> Tom
>
> ______________________________________________
> R-devel@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>
>
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
