> this.is.R
Error: Object "this.is.R" not found
> substitute(this.is.R <- function() X, list(X=!is.null(options("CRAN")[[1]])))
this.is.R <- function() TRUE
> # the above expression as printed is what I want for the function definition
> eval(substitute(this.is.R <- function() X, list(X=!is.null(options("CRAN")[[1]]))))
> this.is.R
function() X
> this.is.R()
[1] TRUE
> X
Error: Object "X" not found
> rm(this.is.R)
> # Try again a slightly different way
> substitute(this.is.R <- function() X, list(X=!is.null(options("CRAN")[[1]])))
this.is.R <- function() TRUE
> .Last.value
this.is.R <- function() TRUE
> eval(.Last.value)
> this.is.R
function() X
> this.is.R()
[1] TRUE
> rm(this.is.R)
>
Why is the body of the function "X" when I substituted a different expression for X? Also, given that the body of the function is X, how does the function evaluate to TRUE since X is not defined anywhere (except in a list that should have been discarded.)
This happens with both R 1.7.1 and R 1.8.0 (under Windows 2000).
(yes, I did discover the function is.R(), but I still want to discover what's going here.)
-- Tony Plate
PS. In S-plus 6.1, things worked as I had expected:
> substitute(this.is.R <- function() X, list(X=!is.null(options("CRAN")[[1]])))
this.is.R <- function()
F
> eval(substitute(this.is.R <- function() X, list(X=!is.null(options("CRAN")[[1]]))))
function()
F
> this.is.R
function()
F
> this.is.R()
[1] F
>
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