Deleting a character from a string w/ substring

; Purpose: Delete a character from the string

; Signature: String -> String

; Examples:
(check-expect (delete-string "learning") "earning")

; Stub:
;(define (delete-string str) "")

; Template:
;(define (delete-string str)
;  (substring "learning" 1 8)) 8=string length

; Code:
(define (delete-string str)
  (substring str 1 (string-length str))
  )