Deleting a character from a string through Index

; Purpose: Given a string and a placeholding index, produce the string at where the character at index is removed.

; Signature: String & Number -> String

; Examples:
(check-expect (string-delete "abc" 1) "ac")
(check-expect (string-delete "str" 2) "st")

; Stub:
;(define (string-delete str index) -1)

; Template:
; (define (delete-string str index)
;  (substring ... ... ...)
;  )

; Code:
(define (string-delete str index)
  (string-append (substring str 0 index)(substring str (+ index 1) (string-length str)))
  )