[plt-scheme] why doesn't DrScheme allow define within define?

wuyanbo wrote:

>Does anyone know why DrScheme doesn't allow this kind of structure. 
>
>(define (main)
>    (define (function)
>        ..
>        ..)
>(function))
>
>
>error message given by Drscheme
>
>"define: found a definition that is not at the top level"
>  
>
Did you remember to change the language level to one of the PLT languages?

-- 
Jens Axel Søgaard