How to set a rule that's too deep for UpValue?

Question

I want to automatically transform Conjugate[a CenterDot[x, y, z]] to Conjugate[a] Conjugate[CenterDot[x, y, z]]. However, the following rule doesn't work:
CenterDot /: Conjugate[coeff_ CenterDot[content___]] := Conjugate[coeff] Conjugate[CenterDot[content]]

and the error message is TagSetDelayed::tagpos: Tag CenterDot in Conjugate[CenterDot[content___] coeff_] is too deep for an assigned rule to be found.
How to achieve my original transformation?

Carl Woll · Accepted Answer

This is a complete hack, but maybe you could try:
Clear[CenterDot]
CenterDot /: a_ b_CenterDot := Module[{stack=Stack[_]},
    foo[a, b] /; MatchQ[stack, {___, HoldForm[_Conjugate], _, _}]
]

foo /: Conjugate[foo[a_, b_]] := Conjugate[a] Conjugate[b]

Example:
Conjugate[x CenterDot[a, b, c] z + 3]

3 + Conjugate[x z] Conjugate[CenterDot[a, b, c]]

Suba Thomas · Answer

Times is not too deep.
Unprotect[Times];
Times /: Conjugate[coeff_ CenterDot[content___]] := 
 Conjugate[coeff] Conjugate[CenterDot[content]]

How to set a rule that's too deep for UpValue?

2 Answers

Add your own answers!

Ask a Question