cacheSweave <- function(name, expr, envir = parent.frame()) {
    if(!file.exists(name)) {
        env <- new.env()
        local(eval(expr), env)
        save(list = ls(env, all.names = TRUE), file = name, compress = TRUE,
             envir = env)
        for(n in ls(env, all.names = TRUE))
            assign(n, get(n, env), envir)
    }
    else
        load(name, envir)
}