class(23)       # numeric
class(2.3)      # numeric
class(NaN)      # numeric

class("Hello")  # character
class("23")     # character

class(TRUE)     # logical
class(FALSE)    # logical
class(T)        # logical
class(F)        # logical
class(NA)       # logical

class(class)    # function
class(print)    # function

