"Write some code that, given any number, will output it's factorial (ie given n, output n!)." <- function(n)
{
  ifelse(n, n*`Write some code that, given any number, will output it's factorial (ie given n, output n!).`(n-1), 1)
}

`Write some code that, given any number, will output it's factorial (ie given n, output n!).`(5)