Provides infrastructure to accurately measure and compare
        the execution time of R expressions.
c(person("Olaf", "Mersmann", role=c("aut")),
        person("Claudia", "Beleites", role=c("ctb")),
        person("Rainer", "Hurling", role=c("ctb")),
        person("Ari", "Friedman", role=c("ctb")),
        person(given=c("Joshua","M."), family="Ulrich", role="cre",
               email="josh.m.ulrich@gmail.com"))
On a Unix-alike, one of the C functions
mach_absolute_time (macOS), clock_gettime or gethrtime. If none
of these is found, the obsolescent POSIX function gettimeofday
will be tried.
Olaf Mersmann [aut],
  Claudia Beleites [ctb],
  Rainer Hurling [ctb],
  Ari Friedman [ctb],
  Joshua M. Ulrich [cre]