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(define (add-streams s1 s2)(cond((stream-null? s1)s2) ((stream-null? s2)s1) (else (cons-stream (+ (stream-car s1) (stream-car s2)) (add-streams (stream-cdr s1) (stream-cdr s2)))))) (define fibs (cons-stream 0 (cons-stream 1 (add-streams (stream-cdr fibs) fibs))))