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Mar
28
comment Dynamic boundaries for FindRoot
Note that ReleaseHold is best inserted inside Catch: Catch[FindRoot[...], findRootTag, ReleaseHold[#1]&] instead of ReleaseHold@Catch[...]. You can study the difference between the two constructs with the following simple four examples: wrapper@Catch[a; b; c, _], wrapper@Catch[a; Throw[b, tag]; c, _], Catch[a; b; c, _, wrapper], Catch[a; Throw[b, tag]; c, _, wrapper].
Mar
28
comment Dynamic boundaries for FindRoot
This is a bit tricky indeed. What you could do is Throw[With[{tmpx = x}, Hold@{x -> tmpx}], findRootTag] and then ReleaseHold it after it has been Catched.
Mar
28
comment Dynamic boundaries for FindRoot
You have many choices to accomplish that: Table[If[EvenQ[i], i], {i, 7}] /. Null -> Sequence[], or Table[If[EvenQ[i], i, Unevaluated@Sequence[]], {i, 7}], or using Reap/Sow again.
Mar
28
comment Dynamic boundaries for FindRoot
Do you mean this: define FindRoot::outside = "A step fell out of the allowed region." and then Check[FindRoot[..., StepMonitor :> If[x<y, Message[FindRoot::outside]], ...], $Failed]? However, the main problem is that you cannot interrupt FindRoot but with Throw.
Mar
28
comment Efficient method for inverting a block tridiagonal matrix
I didn't use the formula on Wikipedia precisely because of that. You have to work them out by hand. The reason is that who wrote them deduced them under the assumption of commutativity of multiplication; so you can't know what kind of manipulations he has carried out. Fortunately, the task of recovering the correct formulas is sufficiently easy to be done in under 5 minutes.
Mar
27
comment Efficient method for inverting a block tridiagonal matrix
Note that the algorithm requires only the inversion of blocks on the main diagonal. Anyway, if you have zero blocks in place of the upper or lower band, your matrix is actually block-triangular, so that you need to perform only the forward or the backward part of the algorithm (depending whether the matrix is lower or upper triangular).
Mar
27
revised How to determine all cases consistent with constraints
added 2513 characters in body
Mar
27
comment Volterra integral equation : 'literally match the independent variables' message
There is no surprise that it does not work: Mathematica should even invent the problem! (click)
Mar
27
comment How to determine all cases consistent with constraints
@whuber -- You are right, I realized it when I went to bed, too late. Now I fixed it.
Mar
27
revised How to determine all cases consistent with constraints
fixed
Mar
27
revised How to determine all cases consistent with constraints
added 1636 characters in body
Mar
27
comment How to determine all cases consistent with constraints
I'll certainly try to do it as soon as possible. Now, if you excuse me, I would like to go to bed: it's 2AM here. Good night all!
Mar
27
comment Puzzling behavior produced by Exists
We also adopted the same style for posting code: code followed by (* return value *). You just wrote a little more explanation. I'm tired instead, 2AM here... Good night!
Mar
27
comment Puzzling behavior produced by Exists
LOL! Our answers are identical! :D
Mar
27
answered Puzzling behavior produced by Exists
Mar
27
comment Combining two plots which are in two regions
You are welcome