base alternative for string extracts

string_extract_all.R

# Not as quick as stringr but only base, so...
string_extract_all <- function(x, pattern, perl = FALSE, ignore.case = FALSE) {
  re <- gregexpr(pattern, x, perl = perl, ignore.case = ignore.case)
  mapply(

    function(xi, rei, lens) {
        substring(xi, rei, rei + lens - 1L)
    },
    xi = x,
    rei = re,
    lens = lapply(re, attr, "match.length"),
    SIMPLIFY = FALSE,
    USE.NAMES = FALSE
  )
}