[plt-dev] Release Announcement for v4.2.4

I recommend the following wording:

* 2htdp/universe: We have severed the intimate connection between  
universe and the image library. The most important change is that the  
design of world programs now demands the use of _two_ teachpacks:  
2htdp/universe and htdp/image (the old image library) or 2htdp/image  
(the new image library). Furthermore, the callbacks for world programs  
no longer use symbols but strings. The image functions are overloaded  
so that both strings and symbols work as inputs.

For upgrading your world programs, see the new Porting World Programs  
guide in the HtDP/2e section of the documentation.

* htdp/world: The old world teachpack remains deprecated. HtDP/2e  
exclusively uses the new 2htdp/universe library. For backwards  
compatibility, the world teachpack will remain in the distribution  
until the coming summer.










On Jan 26, 2010, at 7:18 AM, Robby Findler wrote:

> On Mon, Jan 25, 2010 at 10:32 PM, Eli Barzilay <eli at barzilay.org>  
> wrote:
>> * Added a porting guide that explains how to turn `htdp/world'
>>  programs into `2htdp/universe' and `2htdp/image' programs.
>
> Replace the above with this:
>
> * In support of 2htdp/image, the 2htdp/universe library no longer  
> explicitly
>  provides an image library. See the (new) porting guide for more  
> details.
>
>> * [Matthias] `error' in teaching languages?  universe/world changes?
>>  `random', `gensym', `current-millisecond', `sleep', `assoc',
>>  `with-i/o-from-to' added?
>
> I think error at least deserves a mention here:
>
> * error in the teaching languages now accepts any arguments and puts
> them together into an error message.
>
> The other stuff sounds too small, but deserves to be in some more
> comprehensive list of changes to the teaching languages.
>
> Robby
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