dots arguments

How can we parse the dots-arguments in a function?

dots <- function(...){
# was cex in the dots-args? parse dots.arguments
cex <- unlist(match.call(expand.dots=FALSE)$...["cex"])
if(is.null(cex)) print("No cex supplied")
else print(gettextf("cex was %s", cex))
}

dots (cex=0.9, another=4)
dots (another=5)