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Re: Defining a function P[A_ | B_]:=f[A,B] overriding Alternatives


Allan Hayes schrieb in Nachricht <7ouvht$osf$1 at dragonfly.wolfram.com>...
>Eckhard:
>Following your idea  n the posting below:
>
>p[HoldPattern[Alternatives][A_ , B_]] := {A, B}
>
>DownValues[p]
>
>{HoldPattern[p[HoldPattern[Alternatives][A_, B_]]] :> {A, B}}
>
>p[a | b]
>
>{a, b}
>
>Allan


Of course, that's the straightforward way to do this. However, the
originator of this thread (Peltio) wrote the following:

>And yet I wanted to be able to define my function without showing the
>Alternatives /: part.

Therefore, I suppose that Peltio's intention was to be able to define p[A_ |
B_] without any explicit manipulation of the behavior of Alternatives. This
can only be achieved by rewriting the DownValues of p.

-- Eckhard

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