[plt-scheme] When is (required ...) required in a formlet?

Thanks.

On Sun, Apr 25, 2010 at 1:14 AM, Jay McCarthy <jay.mccarthy at gmail.com> wrote:
> text-input and password-input are returned (formlet/c (or/c false/c binding?))
>
> This means that they can result in a form binding (if the input was
> entered) or #f if it wasn't.
>
> required turns a (formlet/c (or/c false/c binding?)) into a (formlet/c bytes?)
>
> This means it extracts the form binding value or error if the field
> wasn't entered.
>
> to-string turns a (formlet/c bytes?) into a (formlet/c string?)
>
> You never "need" required, but if you use to-string, then the types
> must match and required is often useful for that.
>
> Jay
>
> On Sat, Apr 24, 2010 at 9:16 PM, Todd O'Bryan <toddobryan at gmail.com> wrote:
>> I just discovered that this formlet
>>
>> (define login-formlet
>>  (formlet
>>   (div "Username:" ,{(to-string (required (text-input))) . => . username} (br)
>>      "Password:" ,{(to-string (required (password-input))) . => . password})
>>   `#hash((username . ,username)
>>          (password . ,password))))
>>
>> doesn't work if I remove the (required ...) wrapping (text-input) and
>> (password-input).
>>
>> I'm fine with that, but I don't really understand what it's doing and,
>> therefore, when I have to include it. Any insight?
>>
>> Todd
>> _________________________________________________
>>  For list-related administrative tasks:
>>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>>
>
>
>
> --
> Jay McCarthy <jay at cs.byu.edu>
> Assistant Professor / Brigham Young University
> http://teammccarthy.org/jay
>
> "The glory of God is Intelligence" - D&C 93
>