strdiff <- function(src, dest)
{
  x <- unlist(strsplit(attr(adist(src, dest, counts = TRUE), "trafos"), ""))
  n <- length(x)
  spos <- 1:(n + 1) - c(0, cumsum(x == "I"))
  dpos <- 1:(n + 1) - c(0, cumsum(x == "D"))
 
  cat(src, "->", dest, "\n")
  for (i in 1:n) {
    if (x[i] == "D" | x[i] == "S") {
      cat(sprintf("-%d:%s\n", i, substr(src,  spos[i], spos[i])))
    }
    if (x[i] == "I" | x[i] == "S") {
      cat(sprintf("+%d:%s\n", i, substr(dest, dpos[i], dpos[i])))
    }
  }
  cat("\n")
}
 
strdiff("abcdef", "abdef")
strdiff("abdef", "bcdef")
strdiff("bcdef", "abcdef")

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