R-alpha: Re: R/R-minus incompatibility [ an old one ]

Mon, 10 Nov 1997 11:43:11 -0500

```>> x[["f"]]<-1
>> zz<-"g"
>In R both variants fail unless the name is already on the list. The
>first one can be replaced by x\$f, but there's seems to be no
>substitute for the other one (oh yes I found one, but it's not fit to

A long time ago it seems it was decided to remain incompatible with S on
this, I think because  people often do this in error. (Indeed, it did
point out some errors in my code.) However, there were some instances in
my code where I did something like x[[c("f","g","h")]] <- 1:3 and wanted
the corresponding elements updated or inserted as appropriate.  I have
replaced those instances with listadd(x, c("f","g","h")) <- 1:3 where
listadd is as defined below (more or less as suggested by Ross or Robert
at the time). It is one of the functions in the compatibility code I
have circulated previously.

Paul Gilbert
________
"list.add<-" <- function(x, replace, value)
{# replace or add elements to a list.
if (is.numeric(replace))
{x[[replace]] <- value
return(x)
}
if (is.null(value))  value <- list(NULL)
if (!is.list(value)) value <- list(value)
if (1 == length(value))
{for (i in seq(length(replace)))
x<- do.call("\$<-", list(x,replace[i],value[[1]]))
}
else
{if(length(value) != length(replace) )
stop("number of replacement values != number of elements to
replace")
for (i in seq(length(replace)))
x<- do.call("\$<-", list(x,replace[i],value[[i]]))
}
x
}

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```