acer

16581 Reputation

29 Badges

14 years, 20 days

On google groups. (comp.soft-sys.math.maple and sci.math.symbolic)

On stackoverflow.

On math.stackexchange.com.

MaplePrimes Activity


These are replies submitted by acer

@Carl Love My guess is that the spirit of that is to convey that -- when called alone -- `eval` does not change the stored values.

Sure, doing so might toggle some flag or DAG bit, which could be utilized to affect subsequent rtable_eval behavior.

Getting both convenient and highly efficient behavior under all circumstances seems difficult for mutable data structures -- given the need for in-place semantics and the variety of evaluation circumstances. I suppose that it is a push-me-pull-me thing, where concessions in some respects accompany benefits in others.

@HuanLuong Nobody wants to have to type in all your code, so as to try and reproduce the issue so as to diagnose it.

A screenshot image is not code that can be easily copied.

It's impolite of you to expect an answer without providing the code to reproduce. You've even ignored a explicit request to do so.

@radaar You could use,

    catch "no improved point":

or,

    catch:

where the second of those would catch any error. You can thus catch specific errors (whose messages start a certain way), or most all errors.

 

@V1 ...because you couldn't be bothered to do so.

You have posted only an image of your code, and no means to reproduce or analyze it via copy & paste. That is useless.

Use the green up-arrow to attach your worksheet, or add in the code-to-reproduce as plaintext.

@nm It is a shame that you removed your Answer, for now the discussion of it seems senseless.

My point is that using an identity on a mere reformulation of itself does not demonstrate much of anything. Even now (with your new response that the identity is not "needed") it's unclear whether you actually understand this point.

@vv Thank you. I realize that it's a tough topic, but I was surprised by the slog I had trying even with cartesian coordinates.

@nm How is it meaningful to my original question to use your identity for the purpose of anything but near-trivial reformulation?

What do you think of this:

restart;

expr := 2*Pi*(-z)^(1/2)-z^(1/2)*(2*ln(-z^(1/2))-ln(z));

2*Pi*(-z)^(1/2)-z^(1/2)*(2*ln(-z^(1/2))-ln(z))

restatement := thaw(isolate(subs(ln(-sqrt(z))=freeze(ln(-sqrt(z))),expr),
             freeze(ln(-sqrt(z)))));

ln(-z^(1/2)) = Pi*(-z)^(1/2)/z^(1/2)+(1/2)*ln(z)

eval(expr, {restatement});

0

 

Download restatement.mw

There's not that much more going on, in using an equivalent one-off or just a reformulation. I was hoping more for a use of stock commands to provide any intermediary normalizations.

I wonder whether the submitter has noticed the recovery of most of his semester's work.

@SirFrancisBacon Remove this line from your code, if you still have it:

  constants := D_e, a, R_e

@Adam Ledger I corrected it using the vi editor, looking at the .mw file as plaintext XML.

It happens that I happen to be quite familiar with the XML plaintext format of a worksheet.

This example was not difficult. I recovered all that was actually present and recoverable.

This example from a day or so earlier was slightly more interesting (and it is large, and a great deal more was recovered).

@sand15 I consider it a weakness that simplify is not trying to obtain a normal form (in terms of radicals) for the whole expression as one kind of preliminary step. That seems a natural thing to attempt here, since the expression contains radicals and is of modest size, complexity, and degree.

I did not explicitly state that I consider it a bug because it does not try expand on the whole expression. Perhaps it ought to call expand on the whole expression as one avenue of attack -- I leave that for someone else to figure out. But I do think that it could try radnormal or evala.

The simplify command must involve some heuristics, on practical grounds. I think that this example merits at least consideration by whoever is most expert in its workings.

Have I understood your question properly?

You need to specify how you want B and C to change with respect to each other during the animation. Otherwise your question is ambiguous.

What is the end goal? By which I mean, what do you intend on doing with these piecewise constructs?

Are you going to ever doing anything other than evaluate them at specific points? If not then why incur the heavy cost of constructing them in the first place? Is there something that you want from these piecewise spline constructs that cannot be done directly using CurveFitting:-ArrayInterpolation or the Interpolation package? Both of the latter can be used to evaluate at specific points more quickly than piecewise splines (even univariate piecewise with ordered lookup that allows for bisection search).

 

1 2 3 4 5 6 7 Last Page 1 of 386