[R] Force evaluation of a symbol when a function is created

[Duncan Murdoch]

Here's one more way.  It seems to me this is the most R-like way to do 
what you want:

   multiply_by_Y <- function(Y) {
     force(Y)
     function(x) x*Y
   }

   F <- multiply_by_Y(3)

The "force" call forces Y to be evaluated at that point, so its value is 
fixed from that point forward.

Duncan Murdoch

On 12-08-06 5:07 PM, Schoenfeld, David Alan,Ph.D.,Biostatistics wrote:
>
> I am porting a program in matlab to R,
> The problem is that Matlab has a feature where symbols that aren't arguments are evaluated immediately.
> That is:
> Y=3
> F=@(x) x*Y
>
> Will yield a function such that F(2)=6.
> If later say. Y=4 then F(2) will still equal 6.
>
> R on the other hand has lazy evaluation.
> F<-function(x){x*Y}
> Will do the following
> Y=3
> F(2)=6
> Y=4
> F(2)=8.
> Does anyone know of away to defeat lazy evaluation in R so that I can easily simulate the Matlab behavior.  I know that I can live without this in ordinary programming but it would make my port much easier.
>
> Thanks.
>
>
>
>
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