Problem with scoping a variable value

On Thu, 16 Feb 2006, Tolga Uzuner wrote:

I have a function which has a variable called show as an input:

richardson.grad <- function(func, x, d=0.01, eps=1e-4, r=6, show=F){
# do some things
  if(show) {

       cat("\n","first order approximations", "\n")
       print(a.mtr, 12)


   }
#do more things and return
}

The show variable is being used as a flag to show intermediate results.

Interestingly enough, I have downloaded a package recently which defines
the show variable as a function:

show

standardGeneric for "show" defined from package "methods"

function (object)
standardGeneric("show")
<environment: 01676F7C>
Methods may be defined for arguments: object

Now, all of a sudden, the function I had defined earlier is scoping up
to this new value, and is thus not working:

richardson.grad(function(x) x^2,2)

Error in if (show) { : argument is not interpretable as logical

I could always redefine show in richardson.grad to be something else but
something seems wrong: why is richardson.grad not looking up show's
value in the  function ? How would I fix this ?

You didn't spell out the logical value 'FALSE' which may
be causing your problem. Consider this alternative also...

richardson.grad <- function(func,
                            x,
                            d = 0.01,
                            eps = 1e-4,
                            r = 6,
                            verbose = getOption("verbose")) {
    ## do some things
    if (verbose) {
         cat("\n", "first order approximations:", "\n")
         print(a.mtr, 12)
    }
    ## do more things and return
}