[racket] Generics and modules

From: Greg Hendershott (greghendershott at gmail.com)
Date: Thu Aug 29 21:49:58 EDT 2013

On Wed, Aug 28, 2013 at 5:07 AM, Tobias Hammer <tobias.hammer at dlr.de> wrote:
> On Tue, 27 Aug 2013 20:03:43 +0200, Greg Hendershott
> <greghendershott at gmail.com> wrote:
> . is only special when surrounded by spaces abc.def is a perfectly valid
> variable name (as is abc. and .abc).

Oh, wow. Very early on learning Scheme, I somehow got the idea that
`.` was special in the same way as `,`. Thanks for correcting that!

> Attaching a prop:procedure would be sufficient and only impacts the struct
> access itself, not every statement.

You're right, it's sufficient if you only want it to work when the
dict is in the first position:

    (a-dict key)

But alas I also want it to work in the second position:

    (key a-dict)

Because only that composes with the threading macro -- so that this:

    (~> a-dict k0 k1 k2)

Expands to this:

    (k2 (k1 (k0 a-dict)))

And is `#%app`lied as this:

    (dict-ref (dict-ref (dict-ref a-dict k0) k1) k2)

As explained here:


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