[racket] Is this a good design

 >> A couple of comments:
 >>
 >> * `string-first` (- instead of the _) is a more idiomatic naming

Oke, changed that.

 >>  * (eq? (string? s) true) is >> verbose. (string? s) already returns 
a boolean.

I changed that , thanks for the tip.

* Generally, when writing programs using the design recipe you don't 
need to think of the error cases (e.g., when the contract is violated) 
like `s` not being a string. You may want to think of some edge cases 
though (how long can a string be?).

I know I can check on empty strings but the exercise says that I don't 
have to consider empty strings.
That's why I did not check on that.

With all the remarks I changed the function to this :

;String -> String
    ;This function takes out the first character of a given string with 
the name s
    ; given "roelof" expect "r"
    ; given "example" expect "e"
    (define (string-first s)
      (if (string? s)
          (string-ith s 0 )
          "You have not entered a string"))

Roelof