Note that the #PrettyPrinting dispatch tables of #CommonLisp conceptionally are a #GenericFunction with #ParametricDispatch.
The function SET-PPRINT-DISPATCH is essentially an ADD-METHOD to the pretty printing parametric dispatch.
(Unfortunatly, the canonical, #ProofOfConcept implementation of PP by #RichardWaters is one single convoluted mess; basically a negative example of software design, even by standards of its time.)
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