[plt-scheme] HtDP languages + emacs

> >      (draw-solid-disk (make-posn 100 50) 10 'red)  -> reference to
> >     undefined identifier: make-posn
>
> Use the lang collection.
>
>    (require (lib "htdp-advanced.ss" "lang"))
>    (make-posn 1 2)
>
> See collects/lang/doc.txt for more info.

Ah, ok. Now I see what is happening. Thanks for the pointer.

I am fairly comfortable with Scheme but new to graphics programming.
So I am exploring the examples in dr scheme and HtDP. After some more
exploring I have decided to "work my way up" from the mred toolbox.

But I still have a more general question. I assume that plt scheme has
built a graphics abstraction layer (mred?) and that different graphics
modules (ultimately) call it. If so, is there an efficient way to
trace back from a particular module to see the different dependies? (I
tried this with  draw.ss and quickly got lost.)

thanks.

k.