On 1/7/2019 2:23 PM, Neil Van Dyke wrote:
George Neuner wrote on 1/7/19 1:12 PM:
Your examples look a lot like what is possible using Lisp's generic
functions: specifically "before", "after" and "around" functions.
Before/after/around are what I call "advice". Advice is a lifesaver
when you need it and there's no good documented interface. For
example: "I really-really-really need that one function in that
library I use to work differently, but I'm not allowed to modify that
library, and I plan to quit this job before anyone else sees my code
or tries to update to a new version of that library". But I don't
think of advice as good for documented and maintainable code for
software engineering.
13 of one, baker's dozen of the other. <grin>
Though I mostly agree with you, your "advice" does have its uses:
http://www.gigamonkeys.com/book/object-reorientation-generic-functions.html
in particular see the sections on method combinations.
And this is the "documentation" for generic functions in Lisp:
http://www.lispworks.com/documentation/HyperSpec/Body/m_defgen.htm#defgeneric
http://www.lispworks.com/documentation/HyperSpec/Body/m_defmet.htm#defmethod
The basic generics machinery isn't terribly hard to implement inside a
compiler. I'm not sure though how I would do it on top of Racket. I'm
sure I could hack up some ugly macros that would work, but it seems like
it needs to be a language to be done right.
YMMV,
George
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