How to define a string in Scheme - any string that I choose? - string

Question

Given that:
(define output "")
or that
(define output "goodInput")
When I run those defines in my code, I get:
ERROR: In procedure memoization:
ERROR: Bad define placement (define output "").
Why is that ?
EDIT:
; Formal function of the code
(define (double->sum myString)
(define myVector 0)
(set! myVector (breaking myString))
(define output "")
(define returnValue (checkLegit myVector)) ; check the number of legitimate characters ,they need to be either numbers or "."
(define flag 0)
(if (not(= returnValue (vector-length myVector))) (set! output "Input error") (set! flag (+ flag 1)))
(define i 0) ; the length of the vector
(define count 0) ; the value of all the numbers in the vector
(if
(= flag 1)
(do ()
((= i (vector-length myVector))) ; run until the end of the vector
(cond
((char=? (vector-ref myVector i) #\.) ; check if we found a dot
(set! output (appending output count)) (set! output (appendingStrings output ".")) (set! count 0)
)
(else (set! count (+ count (char->integer(vector-ref myVector i)) )) (set! count (- count 48))
); end of else
) ; end of cond
(set! i (+ i 1)) ; inc "i" by 1
); end of do
) ; end do
; if flag = 1 , then the input is in a correct form
(if (= flag 1) (set! output (appending output count)))
(if (= flag 1)
output
"Input error")
) ; END

Answer 1

The problem is not in the string definition itself (there are no strange characters, or anything like that), it's in the place within the code where that definition is happening: you're inside a procedure, and the last line in a procedure can not be a define. Try returning something after the definition and it should work fine.
I guess that you've just started writing the procedure, just keep going after the define and write the rest of the code. For the time being, use a placeholder value at the end, so the interpreter won't complain:
(define (double->sum myString)
(define myVector 0)
(set! myVector (breaking myString))
(define output "")
'ok)
Also a matter of style - although it's ok to define-and-set a variable like that, it's more idiomatic to use a let expression for defining local variables. This is what I mean:
(define (double->sum myString)
(let ((myVector (breaking myString))
(output ""))
'ok))
In that way, you won't have to use set!, which mutates the variable and goes against the functional-programming style preferred in Scheme.