decode.R

decode <- function(x, search, replace, default = NULL) {

    # build a nested ifelse function by recursion
    decode.fun <- function(search, replace, default = NULL)
        if (length(search) == 0L) {
            function(x) if (is.null(default)) x else rep(default, length(x))
        } else {
            function(x) ifelse(x == search[1L], replace[1L],
                                                decode.fun(tail(search,  -1L),
                                                           tail(replace, -1L),
                                                           default)(x))
        }

    return(decode.fun(search, replace, default)(x))
}