Inf and lazy evaluation
R is lazy, but not quite that lazy ;-) It's likely much easier to do this with regexps something like list.files()[grepl(paste0(filename, "-"[0123456789]+""), list.files())] Michael
On Mon, May 14, 2012 at 3:34 PM, J Toll <jctoll at gmail.com> wrote:
Hi, I have a question involving Inf, lazy evaluation, and maybe argument recycling. ?I have a directory where I am trying to check for the existence of files of a certain pattern, basically something like "filename-#", where # is an integer. ?I can do something like this, which works. file.exists(paste(filename, "-", 1:100, sep = "")) But I don't like the fact that I am only checking the first 100 possibilities. ?What I would prefer is this: file.exists(paste(filename, "-", 1:Inf, sep = "")) But that doesn't work, I get the error: Error in 1:Inf : result would be too long a vector On one hand, with lazy evaluation, you would think that 1:Inf should work. ?On the other hand, I'm not quite sure what the output would be if it was working, especially if there were large gaps in the integers. ?Is there a way to get the behavior I seek (i.e. the lazy evaluation of 1:Inf). Thanks, James
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