Detect duplicated function definitions from R source files

function_duplicates.R

#!/usr/bin/env Rscript

f <- list.files("R/", full.name = TRUE) # run from package source, or adjust path
d <- lapply(setNames(f, sub("//", "/", f)), function(x)
{
    x <- readLines(x)
    names(x) <- seq_along(x) # tag line number
    x <- sub("#.*", "", x) # delete comments
    x <- sub("^[\ \t]*", "", x) # delete leading whitespace
    x <- x[grepl("function", x)] # get function definitions
    x <- sub("[\ ]+.*", "", x) # get function names
    x
})
d <- unlist(d)
d <- d[order(d)]
d <- d[d %in% unique(d[duplicated(d)])]
cat("duplicated functions:\n")
null <- Map(function(n,v){cat(n, ": ", v, "\n", sep = "")}, names(d), d)

shell version (without file and lines):
sed -e 's/^[\ \t]*//' -e 's/#.*//' R/* | awk '/function/{print $1}' | sort | uniq -d

with file and line information:
grep -n -f <(sed -e 's/^[\ \t]*//' -e 's/#.*//' R/* | awk '/function/{print $1}' | sort | uniq -d) R/* | grep function

also:
for f in $(sed -e 's/^[\ \t]*//' -e 's/#.*//' R/* | awk '/function/{print $1}' | sort | uniq -d); do echo $f; grep -n "$f" R/* | sed 's/#.*//' | grep function; done