Infinite lists in Scheme: Streams

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Lecture 5 - Page 23 : 26

Functional Programming in Scheme
The Order of Evaluation

Infinite lists in Scheme: Streams

We can work with lists of infinite length by delaying the evaluation of every list tail using delay

As an invariant, every list tail will be delayed

(cons-stream a b)   ~   (cons a (delay b))

(define head car)

(define (tail stream) (force (cdr stream)))


(define empty-stream? null?)

(define the-empty-stream '())

Stream primitives. Notice the way head is defined to be an alias of car.

An implementation of cons-stream in R5RS Scheme.

The functions mentioned above stem from the book Structure and Interpretation of Computer Programs

SICP: Streams