exercise-8.scm (393B)
1 (define-library (sicp solutions chapter-3 exercise-8) 2 (import (scheme base)) 3 (export 4 make-f 5 ) 6 7 (begin 8 (define (make-f) 9 (define first-internal-value 'still-undecided) 10 11 (define (f x) 12 (if (eq? first-internal-value 'still-undecided) 13 (begin 14 (set! first-internal-value 15 x) 16 0) 17 x)) 18 19 f)))