Re: [R] function closure

[Ashwani Rao]

Thanks Bill.
Can you please tell me why did you change exp "pattern="*.xml"" to
pattern="\\.xml$".
I know that second one also makes sense.




On Mon, Aug 12, 2013 at 9:59 AM, William Dunlap <wdun...@tibco.com> wrote:

> Change your 'fileIndex <- fileIndex + 1' to 'fileIndex <<- fileIndex + 1'
> so the fileIndex in the environment of the call to generateFiles() is
> altered
> (instead of creating and forgetting about a variable called fileIndex
> in the function created by generateFiles.
>
>   generateFiles <- function(path, pattern="\\.xml$") {
>       files <- dir(path, pattern=pattern, full.names=TRUE, recursive=TRUE,
> no..=TRUE)
>       total <- length(files)
>       fileindex <- 1
>       fileGen <- function() {
>           if (fileindex < total) {
>               fileToReturn <- files[[fileindex]]
>               print(fileindex)
>               fileindex <<- fileindex + 1
>               fileToReturn
>           }
>       }
>       fileGen
>   }
>
> used as:
>
>   > nextFile <- generateFiles("c:/temp", pattern="\\.R$")
>   > nextFile()
>   [1] 1
>   [1] "c:/temp/4209/test.R"
>   > nextFile()
>   [1] 2
>   [1] "c:/temp/a.R"
>
> Bill Dunlap
> Spotfire, TIBCO Software
> wdunlap tibco.com
>
>
> > -----Original Message-----
> > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org]
> On Behalf
> > Of Ashwani Rao
> > Sent: Monday, August 12, 2013 9:45 AM
> > To: r-help@r-project.org
> > Subject: [R] function closure
> >
> > Hi,
> >
> > Just for fun, I wanted to try function closures.
> > Here  is simple function definition.
> > The following "generateFiles" function return function "fileGen" which
> will
> > return a a regular file in directory , every time a call it (fileGen).
> >
> >
> > generateFiles <- function(path, pattern="*.xml")
> >
> > {
> >
> >         files <- dir(path, pattern="*.xml", full.names=TRUE,
> recursive=TRUE,
> > no..=TRUE)
> >
> > total <- length(files)
> >
> > fileindex = 1
> >
> >         fileGen <- function()
> >
> > {
> >
> > if (fileindex > total)
> >
> > {
> >
> > return(NULL)
> >
> > }
> >
> > fileToReturn <- files[[fileindex]]
> >
> > print(fileindex)
> >
> > fileindex <- fileindex + 1
> >
> > return(fileToReturn)
> >
> > }
> >
> > return(fileGen)
> >
> > }
> >
> >
> > I am incrementing the value of variable "fileindex" in the function
> > "fileGen" , everytime I call this function.
> >
> > But the value of fileindex remains 1 , no matter how many times i call
> > "fileGen()".
> >
> > Can you please tell me how to change the value of fileIndex so as in
> > subsequent call to "fileGen" will reflect this.
> >  --
> > अश्वनी प्रताप
> >
> >       [[alternative HTML version deleted]]
>
>


-- 
अश्वनी प्रताप

        [[alternative HTML version deleted]]


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