As the error message states, you have a problem with the cond, in particular with the parens.
I like to use brackets to denote the cond and actions like this: (cond [(condition1) value1] [(condition2) (action2)] [else (else-action)] ) Hope this helps, Kieron On Oct 8, 2012, at 8:11, Ashley Fowler <afowl...@broncos.uncfsu.edu> wrote: > Well this is what I got so far... > > (define deleteNth > (lambda(N LS) > (cond > (null? LS) LS) > ((= N 0)(cdr LS)) > (else(cons(car LS)(deleteNth(- N 1)(cdr LS)))))) > > and it keeps giving me the error of "cond: bad syntax (clause is not a > test-value pair) in: ls" > From: Matthias Felleisen [matth...@ccs.neu.edu] > Sent: Monday, October 08, 2012 9:51 AM > To: Ashley Fowler > Cc: users@racket-lang.org > Subject: Re: [racket] Delete Nth Term > > > 3 versions, all pass the test suite. Now write the function > > pick-one-of-three : [List X X X] -> X > > and turn in. > > > > > #lang racket > > (require rackunit) > > ;; Nat [Listof X] -> [Listof X] > ;; delete the n-th item from l, if there is one > > (module+ > test > (check-equal? (deleteNth 4 '()) '()) > (check-equal? (deleteNth 0 '(a b c)) '(b c)) > (check-equal? (deleteNth 3 '(a b c)) '(a b c)) > (check-equal? (deleteNth 2 '(a b c)) '(a b)) ) > > (define (deleteNth n l) > (cond > [(= n 0) (rest l)] > [(< n (length l)) (append (take l n) (rest (drop l n)))] > [else l]) > #; > (cond > [(empty? l) l] > [(zero? n) (rest l)] > [else (cons (first l) (deleteNth (sub1 n) (rest l)))]) > #; > (cond > [(and (zero? n) (empty? l)) l] > [(and (positive? n) (empty? l)) l] > [(and (zero? n) (cons? l)) (rest l)] > [(and (positive? n) (cons? l)) (cons (first l) (deleteNth (sub1 n) (rest > l)))])) > > > > > > On Oct 7, 2012, at 10:03 PM, Ashley Fowler wrote: > >> I need help with making a function that deletes the nth term from a >> list.(list LS with its Nth element (with indexes >> starting at 0) deleted) >> So far I have >> >> (define (deleteNth N ls) >> (if (null? ls) >> ls >> (deleteNth (- N 1) (cdr ls)))) >> >> The results should be ... >> >> (deleteNth 4 '()) returns () >> (deleteNth 0 '(a b c)) returns (b c) >> (deleteNth 3 '(a b c)) returns (a b c) >> ____________________ >> Racket Users list: >> http://lists.racket-lang.org/users > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users
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