No, it looks like the diagonal entries cannot be replaced by anything but zero while still maintaining the option shape=antisymmetric.
> generators[1,1]:=Matrix(4,4);
Error, attempt to assign non-zero to antisymmetric diagonal
This seems wrong to me. Why couldn't the restriction on the diagonal elements instead be that a[i,j]=-a[i,j] ? That way, having rtables on the diagonal might be possible. Well probably still not, since evalb(a=-a) doesn't return true for zero-matrix `a`. But it would have been nice if you could have done, directly,
generators := Matrix(4,4,
(a,b) -> `if`(a=b,Matrix(4,4),
metric . Matrix(4,4,
(c,d) -> metric[a,c]*metric[b,d] - metric[b,c]*metric[a,d])),
shape=antisymmetric);
I don't see a `index/antisymmetric` or `index/skewsymmetric` routine, so the antisymmetric indexing function looks built-in. You could try creating your own Antisymmetric indexing function with something more sophisticated for handling the diagonal's qualities.
acer
I second the idea of a longer (or expandable) list of "Recent comments".
An exapandable "Active forum topics" would also be nice. And I don't mean like its current "more", which immediately leads to too many choices to scan. I mean just like the sidebar, but longer. A problem with the MaplePrimes Forums's pages is that it's only possible to see the whole thread, and it's not possible to get to just the last entry posted in each.
So once an entry gets pushed off the main page and sidebars, it's difficult to access easily.
Also, could someone please improve the tracking pages of each individual. Instead of just showing a single entry to each forum topic, perhaps it could list each entry separately. That way, one could get to the users posts directly.
acer
Trying to be tricky.
unprotect(LinearAlgebra:-Multiply);
Z:=copy(LinearAlgebra:-Multiply):
LinearAlgebra:-Multiply:=proc()
if args[1]=`#mo("∇")` or args[1]=`#mo("∇")` then
args[1](args[2]);
else
Z(args);
end if;
end proc:
`#mo("∇")`:=proc(V::Vector) map(sin,V); end proc:
`#mo("∇")`:=`#mo("∇")`:
Now insert the Del symbol from the palette, and toggle it as Atomic Identifier, and it can be used without the brackets. That is to say, I was able to do 2D things like,
V
V V
I didn't check to see whether I'd broken LinearAlgebra:-Multiply. I could still do,
V V
There may be some simple way to customize it, which someone else can suggest. It might also be possible to use instead a module for the redefined multiplication, but I didn't try.
acer
Trying to be tricky.
unprotect(LinearAlgebra:-Multiply);
Z:=copy(LinearAlgebra:-Multiply):
LinearAlgebra:-Multiply:=proc()
if args[1]=`#mo("∇")` or args[1]=`#mo("∇")` then
args[1](args[2]);
else
Z(args);
end if;
end proc:
`#mo("∇")`:=proc(V::Vector) map(sin,V); end proc:
`#mo("∇")`:=`#mo("∇")`:
Now insert the Del symbol from the palette, and toggle it as Atomic Identifier, and it can be used without the brackets. That is to say, I was able to do 2D things like,
V
V V
I didn't check to see whether I'd broken LinearAlgebra:-Multiply. I could still do,
V V
There may be some simple way to customize it, which someone else can suggest. It might also be possible to use instead a module for the redefined multiplication, but I didn't try.
acer
A quick peek at the code Library code of the depends() routine shows a bit of the logic. That is, by issuing,
showstat(depends);
It looks as if `depends` returns false if `has` returns false (modulo some indexed name funny business). The converse is the interesting question, I suppose.
The routine `depends/internal` does further analysis, and you can see how it handles some special structures with another showstat() call on it.
Having peeked, a little imagination can conjure up some cases that are missing. For example,
> a := SDMPolynom(t^3+5*t^2+11*t+15,t);
3 2
a := SDMPolynom(t + 5 t + 11 t + 15, [t])
> has(a,t);
true
> depends(a,t); # whoops
Error, (in depends/internal) invalid input: depends/internal uses a 2nd
argument, x, which is missing
I don't know whether you consider the `x` in a data structure like SDMPolynom -- which represents a polynomial -- to be a dummy variable or not.
acer
A quick peek at the code Library code of the depends() routine shows a bit of the logic. That is, by issuing,
showstat(depends);
It looks as if `depends` returns false if `has` returns false (modulo some indexed name funny business). The converse is the interesting question, I suppose.
The routine `depends/internal` does further analysis, and you can see how it handles some special structures with another showstat() call on it.
Having peeked, a little imagination can conjure up some cases that are missing. For example,
> a := SDMPolynom(t^3+5*t^2+11*t+15,t);
3 2
a := SDMPolynom(t + 5 t + 11 t + 15, [t])
> has(a,t);
true
> depends(a,t); # whoops
Error, (in depends/internal) invalid input: depends/internal uses a 2nd
argument, x, which is missing
I don't know whether you consider the `x` in a data structure like SDMPolynom -- which represents a polynomial -- to be a dummy variable or not.
acer
He was asking whether depends() and has() are equivalent, aside from cases using "dummy" variables like for Int and Sum, etc.
acer
He was asking whether depends() and has() are equivalent, aside from cases using "dummy" variables like for Int and Sum, etc.
acer
Well, yes. Exactly. For 2D input, the space between the function name and the brackets is parsed as a multiplication, while in 1D input it's parsed as a function call.
Having different parsers behave in different ways on things like this is not good.
acer
Well, yes. Exactly. For 2D input, the space between the function name and the brackets is parsed as a multiplication, while in 1D input it's parsed as a function call.
Having different parsers behave in different ways on things like this is not good.
acer
Another trap: If a space is inserted between the `int` and the open-bracket then the parsed meaning is different in 1D and 2D input.
acer
Another trap: If a space is inserted between the `int` and the open-bracket then the parsed meaning is different in 1D and 2D input.
acer
Yes, and there are connections between the authors. Aside from papers on calculating Pi, etc, there also seems to have been some
contention in the past, though I know nothing about the truth of it all.
acer
You have described close to the usual way in which LaTeX output, and Maple's latex() command, are supposed to work.
But, instead of having to copy the .sty files all over, it should be possible to just append the TEXINPUTS environment variable with /etc (or \ETC I guess, if you use Windows). That environment variable is used by latex and tex as a search path.
acer
I hardly ever use any CAS other than Maple.
I sometimes use Matlab. But even then, it is mostly for Simulink. I usually do that from Maple's own evalM() command. On occasion, I will benchmark parts of the two systems.
I only very rarely use Mathematica. I do not like Mathematica's model for numerical computations.
acer
