itsme

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12 years, 181 days

MaplePrimes Activity


These are replies submitted by itsme

@rlopez 

thanks for your comment.

yup, i did notice that Typesetting:-Typeset indeed does the trick. It could be a good idea to include this info into the docs for typeset however. Right now, there isn't a mention of this kind of behavior in the help page for typeset. The page also does not link to the Typesetting package.

 

 

@Alejandro Jakubi 

if you're implying running maple from command line, and exporting from there (i.e., via plotsetup), then i would strongly advise against this. plotting from cli is completely broken in maple.

@acer 

yup, things seem to align more reasonably now. Thanks for submitting a bug report about this.

@tomleslie 

The OP's first post was titled Euler-Lagrange equations,

I somehow missed the OPs title - i don't even know how that is possible since i had to click it... long day maybe.  ..which would make your link fully relevant - my bad.

@tomleslie 

 

I included the link to be sure we're talking about the same help page - those can change from release to release.

Well, at least I understood that the OP wants to know how to differentiate a function with respect to a variable that itself is a function.

Finding EL equations in general would of course not be the same thing...

While this is clearly not the case in the F that OP defines, if one had a slightly modified version such as say

F:=D(y)(x)^2-y(x)^2+2*y(x)*x^2  + ((D@@2)(y)(x))^2;

then the EulerLagrange will (as expected) give a different results than Physics[diff]:

convert(EulerLagrange(F,x,D(y)(x)),diff);

convert(Physics[diff](F, D(y)(x)), diff); #different than above!

Your code clearly works here, but to be honest I'm not sure that you're using the EulerLagrange method as intended - I would guess that the third argument is not expected to be a derivative. Note also that if F was defined in terms of the "diff" operator and not "D", your code would not work.


P.S. I think your y should be y(x) in the last term of F - this has no effect on the discussion (so far).

@tomleslie 

while certainly relevant, IMO that help page is not particularly helpful in answering OP's question.

See for yourself:

http://www.maplesoft.com/support/help/Maple/view.aspx?path=VariationalCalculus%2fEulerLagrange

@Carl Love 

yup - agreed. i also check the copied results... but as long as only "standard" variable names are used (this includes ones with double underscores), copy/pasting seems fairly reliable.

@hpc 

I feel your pain with getting maple's results into latex. Within the last week alone, I probably copied at least 50 lines of maple's output into latex... but manually. The latex that maple produces by default, is not really usuable in my experience.

 

 

@hpc 

well..  i meant the "extra space" as in the space in the variable you've initially defined.

or put another way, the copied variable has no space while the original, defined as "de" does.


The point of course is that one would probably expect that simplify(a-b) should give 0 because the two expressions would be the same - but they're not as far as maple is concerned - the process of copy/pasting altered one of them.

@hpc 

You're wolceme.

... but as I was saying, you should be careful with using the de as you've defined it. It's really easy to run into weird problems when you need to copy/paste code. It's trivial here, but when you have more complicated expressions that you have to deal with, finding this problem could take a while. So having a "guarantee" that variable names copy/paste properly is quite important.

In the example below the problem goes away (at least here) if one defines:
de:=`δx`;  #no space



 

here is the raw code:

de:=` δx`;
a:=de * 3;
de;
#copy paste the delta x from the 2d math from Eq above , into the next expression to to define b:
b:= δx * 3 ;
simplify(a-b);
#again copy paste the two - note now there is an extra space
#in one of them, between the quotes! - the delta we've defined
#is not the same as what got copied!
3*` δx`-3*`δx`

@Alejandro Jakubi 

i have - in the past.

@Alejandro Jakubi 

Hi Alejandro:

just to chime in with my 2 cents here...

I didn't interpret Acer's narrative as even remotely similar to Wolfram's... Ironically, he's usually the first (!) to tackle questions that require some changes/tinkering with maple's internals - as is the case with my current question.

I think we have to be realistic about the "openness" of Maple - it is not an open source project - it's a closed source platform, with its main goal being that of making money for Maplesoft. This is completely fine... (even though far from optimal for many users).

IMO the best way to ensure the existence of fully open and transparent tools, is to contribute to the various open projects that have been slowly gaining momentum over the last few years - SAGE seems like a good choice...

 

@acer 

thanks for your answer... seems more time consuming that i can afford right now, but maybe will look at this in the future if it doesn't get picked up during the next point release.

@acer 

ok, so to be clear, I guess you you mean that, if I say have an mla file that contains some module named Foo, there is no way for me to print all the source code of that module?

 

@acer 

thanks - that's what i suspected. How would I see the whole module then? I.e. the full code for everything that I need in order to redifine my own version of Explore. Is that possible?

thanks!... (sorry if this is in the docs - if so, i am not able able to find it).

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