PPT Slide

First (car)

First extracts the first element of a list

( first ( list ’a ’b ’c ) ) returns A

( first ( list (list ’a ’b) ’c ) ) returns ( A B )

First is the modern ? name for the function car which merely extracts and returns the car (first) field of any dotted pair.

( car (cons ’a ’b ) ) returns A.

A

B

car

cdr

( car ( list 1 2 3 ) ) returns 1

1

2

3

( car ( car ( list ( list 2 3 ) 1 ) ) ) returns 2

1.12

Previous slide

Next slide

Back to first slide

View graphic version