This is a little painful but the data is small enough, with huge speed gains in common operations
icd9_generate_all_(major_fun, short_code = TRUE, env = new.env(hash =
TRUE, baseenv()))
list with two items, the first being an environment, the second being a vector. The environment has short ICD-9 codes as the names, and the sequence number as the contents. The vector contains the codes in order.