require_tailrec_3.m:038: In mode number 1 of function `even1'/1:
require_tailrec_3.m:038:   warning: mutually recursive call to function
require_tailrec_3.m:038:   `odd1'/1 is not tail recursive.
require_tailrec_3.m:053: In mode number 1 of function `even2'/1:
require_tailrec_3.m:053:   error: mutually recursive call to function `odd2'/1
require_tailrec_3.m:053:   is not tail recursive.
require_tailrec_3.m:068: In mode number 1 of function `even3'/1:
require_tailrec_3.m:068:   warning: mutually recursive call to function
require_tailrec_3.m:068:   `odd3'/1 is not tail recursive.