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7:42 AM
Say you define one of the unused operators like ±x_ := {x, -x} ... how do I clear that definition? I can't seem to find a related question on main, but it seems like something that would have been asked before.
oh, I just Clear[PlusMinus], don't I? Ignore me...
7:58 AM
@MartinEnder :)
2 hours later…
10:16 AM
@MartinEnder Can't get simpler than that. :)
3 hours later…
1:02 PM
@Kuba The first upvote was mine; nevertheless, do add more examples if you come across them while there are no other tag name proposals.
Hello, everyone! I would like to know: is there good method to achive the following functionality?
@J.M. sure, thanks.
I mainly use RepacePart[]
elemAdjust[elems_, deg_, i_] :=
Module[{idx, n = Length[elems] - 1, new},
idx = Select[{i - deg - 1, i, i + deg + 1}, 0 <= # <= n &] + 1;
new = Transpose@ConstantArray[elems[[idx]], 2];
Flatten[ReplacePart[elems, Thread[idx -> new]], 1]
Q: Extending built in functionalities tag

KubaWhile we have customization tag I think it would be nice to have more localized one which would group questions like: How to implement custom integration rules for use by NIntegrate How to create custom Graphics primitive? Is it possible to define a new PlotTheme? Is it possible to insert new c...

pts = {P0, P1, P2, P3, P4, P5, P6, P7};
elemAdjust[pts, 2, 1]
elemAdjust[pts, 2, 3]
1:12 PM
Try Flatten[Partition[Array[C, 8, 0], 4, 3, {3, -3}, {}]] for the first, and Flatten[Partition[Array[C, 8, 0], 4, 3, {-1, 1}, {}]] for the second.
@J.M. Thanks:) Is it a general solution to this problem?
@ShutaoTANG Well, you'll need to ponder on how to use the second, third, and fourth arguments of Partition[] for this.
@J.M. Yes, to be honest, I didn't master the other usage of Partition[] apart from basic usage. In addtion, could you know how to calculate the complement of two sets? Like this?
knotsCommon = {0, 0, 0, 0, 0.25, 0.25, 1, 1, 1, 1};
knots1 = {0, 0, 0, 0, 0.25, 1, 1, 1, 1};
Complement[knotsCommon, knots1]
which returns {}, but I hope the result should be {0.25}
@ShutaoTANG but 0.25 is in both lists; what were you expecting from Complement[]?
1:28 PM
@J.M. Now I know Complement[] will delete the duplicate element. In fact, I would like to use knotsCommon minus knots1, then returning the remaining element, like 0.25
@ShutaoTANG That's not how set complement works. As said in the docs, the result is a list of everything in the first list that is not in the second and subsequent lists. But, the numbers in your knots1 are all in knotsCommon!
2:25 PM
@J.M. The problem comes from the B-spline degree elevate. Here is a example
point = {{0, 0}, {4, 4}, {20, 12}, {32, 0}};
knots = {0, 0, 0, 0.25, 1, 1, 1};

pointElevate = {{0, 0}, {8/3, 8/3}, {16/3, 14/3}, {16., 10.}, {24, 8}, {32, 0}};
knotsElevate = {0, 0, 0, 0, 0.25, 0.25, 1, 1, 1, 1};
Graphics[{Opacity[0.5], Red,
BSplineCurve[point, SplineDegree -> 2, SplineKnots -> knots], Blue,
Dashed, BSplineCurve[pointElevate, SplineDegree -> 3,
SplineKnots -> knotsElevate]}]
2 hours later…
4:12 PM
@ShutaoTANG Something like Fold[# /. {a___, #2, b___} :> {a, b} &, knotsCommon, knots1]?
4:24 PM
Can anyone comment on this?
Q: Checking inequalities: How can $x>0,y>0$ yet $x+y$ indeterminate?

U.T.I have the following: $Assumptions = {0 < Ijm1 < Ij < Ijp1 < 1, bpjm1 < 0, bpj < 0, bpjp1 < 0, Ijm1 \[Element] Reals, Ij \[Element] Reals, Ijp1 \[Element] Reals, bpjm1 \[Element] Reals, bjp \[Element] Reals, bpjp1 \[Element] Reals}; x = (1 - bpjp1 Ijp1 + bpjp1 Ijp1^2) ; y = bpj (Ij - Ijm1) (-...

4:45 PM
@VitaliyKaurov I have added better (IMHO) code to that post...
2 hours later…
6:17 PM
So this got reopened:
Q: Are you interested in a Wolfram Workbench Update?

Frank MartinI also posted this on the Wolfram Community site (link below) Last week I attended the Wolfram Tour (which was great). I asked whenever we could expect a new version of Workbench, as the current (public) version 2 is very out dated. They responded that they use a more up to date version internal...

Is there a good reasoning behind reopening? Wouldn't it be better on meta if we keep it?
It's not that it isn't worth having a discussion on this topic, but this post is just so far from a "practical, answerable question". It simply doesn't fit SE. It would fit meta.
3 hours later…
9:24 PM
@Szabolcs doesn't really matter for me where it is, I think it doesn't fit both. I'd even say it fits better here than meta. (I didn't vote to reopen {unless I missclicked in review})
on-topic in meta seems to be only about mma.se site so I don't know.
9:43 PM
@Kuba This is what my question was about. Do you think this would be helpful to other people struggling with the second argument to Dynamic. If so I would post my code as an answer

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