Wrapper around `gregexpr` to find and extract substrings

gistfile1.r

rxmatches <- function (pattern, text) {
    result <-
    mapply(function (positions, t)
               mapply(function (p, l)
                          if (p == -1) NULL else substr(t, p, p + l - 1),
                      positions,
                      attr(positions, 'match.length')),
           gregexpr(pattern, text),
           text)
    # Sanitise to get rid of redundant singleton lists of NULL
    lapply(result,
           function (x)
               if (is.null(x[[1]])) NULL else x)
}