Scheme "Error: (4 6 5 87 7) is not a function" <p>I just asked a similar question and got the answer I needed, but his time I cannot find any extra parenthesis that would be causing this error: "Error: (4 6 5 87 7) is not a function". Is it due to something else? My code takes a number and if it is already in the list, it does not add it. If the list does not already contain the number, then it adds it.</p> <pre><code>(define (insert x ls) (insertHelper x ls '() 0) ) (define (insertHelper x ls lsReturn counter) (cond ( (and (null? ls) (= counter 0)) (reverse (cons x lsReturn)) ) ( (and (null? ls) (&gt;= counter 1)) (reverse lsReturn) ) ( (eqv? x (car ls)) (insertHelper x (cdr ls) (cons (car ls) lsReturn) (+ counter 1)) ) ( else ((insertHelper x (cdr ls) (cons (car ls) lsReturn) (+ counter 0))) ) ) ) (define theSet (list 4 6 5 87)) (display theSet) (display "\n") (display (insert 7 theSet)) </code></pre>