Message-ID: <4E85CA70.30102@gmail.com>
Date: 2011-09-30T13:56:00Z
From: Duncan Murdoch
Subject: documenting a behavior of adding named item to a list
In-Reply-To: <CAE9ddGCmEwx1t7aATrGYrBeKm-eh3azZbnB5wtnVvghkuZkboQ@mail.gmail.com>
On 29/09/2011 11:42 AM, Suraj Gupta wrote:
> Folks,
>
> Per a post to StackOverflow, I'm looking for an opinion on whether something
> should be documented:
> When adding a named item to a list, its guaranteed that the item will be
> added to the end of the list.
I'd say not. There's an easy way to guarantee the order: instead of using
mylist$newname <- 1
use
mylist <- c(mylist, newname=1)
The former construction doesn't necessarily put it last, only when
newname is a new name. The latter guarantees that it goes last.
Currently, you can do something like this:
x <- list(1) # one element list
x[[10]] <- 10 # grows x to a 10 element list, filling in NULLs in
positions 2 to 9
x$newname <- 11 # puts the newname in the 11th position
It's not obvious to me that the newname shouldn't go into the 2nd
position (if I ignore the comments). I wouldn't want to rule that out
as a future change.
Duncan Murdoch
> SO post:
> http://stackoverflow.com/questions/7599349/adding-named-item-to-list-guaranteed-to-append-to-end-of-list/7599610#7599610
>
> This is my first email to r-devel, so I hope this is an appropriate
> question.
>
> -Suraj
>
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>
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