scheme - Mutual recursion in racket, making cond do two things -



scheme - Mutual recursion in racket, making cond do two things -

i have 2 definitions, family tree , person.

; family-tree is: ; (make-person list-of-family-tree symbol number symbol) ; person is: ; (define-struct person [children name date eyes])

i need create "mutually recursive" function counts number of descendants in tree (including person). can't figure out how create cond more 1 thing if status met.

i.e.:

(define (count-descendants person1) (cond [(empty? (person-children person1)) +0] [else (count-descendants (first (person-children person1)))/*also +1 here*/ (count-descendants (rest (person-children person1)))/*also +1 here*/]))

any thought how recursively phone call function on other parts of list, , add together one?

what inquire accomplished begin expression. don't need here. need combine result of 2 recursive calls. in case, need add together 1 (the current person) result of calling count-descendants on every child. error in function utilize first , rest person-children function not designed handle list of persons. when phone call on empty, error because can't person-children of empty. finally, in case person doesn't have children, believe should still counted, homecoming 1 in case. adding up, must end this:

(define (count-descendants person1) (cond [(empty? (person-children person1)) 1] [else (+ 1 (foldl + 0 (map count-descendants (person-children person1))))]))

in here, utilize map count descendants of children of person1, , foldl add together result.

recursion scheme conditional racket mutual-recursion

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