How to make a data construct in R which contains two components, say
x <- (a,b)
, and make two functions to read and return the two components separately, say function 'car(x)' which will return 'a' and function 'cdr(x)' will return 'b'. And we make the components of the construct can also be constructs, say if
a <- (1, 2)
b <- (3, 4)
then 'car(car(x))' will return '1', 'cdr(car(x))' will return '2', 'car(cdr(x))' will return '3' and 'cdr(cdr(x))' will return '4'.
question from:
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