Retrieve and set default values for parameters (par() or not), when NULL.
TT.auto.set(fun = sys.function(which = -1), assign.op = TRUE,
p.env = parent.frame(), set.par = TRUE)
Julien Moeys [aut, cre], Wei Shangguan [ctb], Rainer Petzold [ctb], Budiman Minasny [ctb], Bogdan Rosca [ctb], Nic Jelinski [ctb], Wiktor Zelazny [ctb], Rodolfo Marcondes Silva Souza [ctb], Jose Lucas Safanelli [ctb], Alexandre ten Caten [ctb]