On Fri, 12 Jul 2002, Adaikalavan Ramasamy wrote:
> Is there a function to write protect a matrix or list ?
>
> I have considered making a duplicate copy. But I am wondering if
> alternatives exist. Thanks.
>
You could do this up to a point by defining a class with nonfunctional
subscripting methods> data(trees)
> class(trees)<-c("nowrite",class(trees))
> "[<-.nowrite"<-function(x,...) {stop("Write
protected")}
> "[[<-.nowrite"<-function(x,...) {stop("Write
protected")}
> trees[3,4]<-4
Error in "[<-.nowrite"(*tmp*, 3, 4, value = 4) :
Write protected> trees[3,]<-trees[2,]
Error in "[<-.nowrite"(*tmp*, 3, , value = trees[2, ]) :
Write protected
but this can't protect you against> data(hills)
> trees<-hills
and it doesn't even seem to work on $> "$<-.nowrite"<-function(x,...) {stop("Write
protected")}
> trees$Girth<-trees$Volume
You probably want a duplicate copy.
-thomas
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