On 12-04-29 3:30 AM, Philippe Grosjean wrote:
> Hello,
>
> ?delayedAssign presents substitute() as a way to look at the expression
> in the promise. However,
>
> msg<- "old"
> delayedAssign("x", msg)
> msg<- "new!"
> x #- new!
> substitute(x) #- x (was 'msg' ?)
>
> Here, we just got 'x'... shouldn't we got 'msg'?
>
> Same result when the promise is not evaluated yet:
>
> delayedAssign("x", msg)
> substitute(x)
>
> In a function, that works:
>
> foo<- function (x = msg) substitute(x)
> foo()
>
> Did I misunderstood something? It seems to me that substitute() does not
> behaves as documented for promises created using delayedAssign().
I don't think this is well documented, but substitute() doesn't act the
same when its "env" argument is the global environment. So this works
the way you'd expect:
e <- new.env()
msg <- "old"
delayedAssign("x", msg, assign=e)
msg <- "new"
e$x
substitute(x, e)
I forget what the motivation was for special-casing globalenv().
Duncan Murdoch
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