Alec Mihailovs

Dr. Aleksandrs Mihailovs

4455 Reputation

21 Badges

19 years, 191 days
Mihailovs, Inc.
Owner, President, and CEO
Tyngsboro, Massachusetts, United States

Social Networks and Content at Maplesoft.com

Maple Application Center

I received my Ph.D. from the University of Pennsylvania in 1998 and I have been teaching since then at SUNY Oneonta for 1 year, at Shepherd University for 5 years, at Tennessee Tech for 2 years, at Lane College for 1 year, and this year I taught at the University of Massachusetts Lowell. My research interests include Representation Theory and Combinatorics.

MaplePrimes Activity


These are Posts that have been published by Alec Mihailovs

?subgrel page contains an interesting error example with a very short syllable c. It looks more interesting with other syllables,

subgrel({y=[a,b,averylongsyllable]}, 
    grelgroup({a,b}, {[a,a], [b,a]}));

Error, (in subgrel) generator [a, b, averylongsyllable] 
contains a syllable `averylongsyllable' that is not a generator, 
or the inverse of a generator, of the parent group

Alec

kernelopts(toolboxdir) crashes mserver both in Classic and Standard Maple 12 on Windows Vista (I didn't check the command line).

Alec

I just looked how differential forms are implemented and was quite surprized

with(DifferentialGeometry):
DGsetup([x,y,z],M):
a:=evalDG(dx &wedge dy+2*dy &wedge dz):
lprint(a);

_DG([["form", M, 2], [[[1, 2], 1], [[2, 3], 2]]])

It is an unevaluated function with nested lists as arguments.

Probably, not the worst possible choice since I can imagine few choices that would be worse - strings, for instance. But there are so many other choices that seem much better - antisymmetric Arrays, or tables, for instance. Why lists?

Alec

Multiplication by 0 gives 0 for differential forms, which is wrong. For example,

with(DifferentialGeometry):
DGsetup([x,y],M):
a:=dx &wedge dy: 
3*a;
                              3 dx ^ dy
0*a;
                                  0

It should be 0 dx^dy.

That reminds me of an old Matrix bug with M^0 being 1 instead of the identity Matrix for square Matrices.

Alec

I just noticed that usual parentheses work as square brackets for Matrices,

M:=Matrix(2,[a,b,c,d]);

                                 [a    b]
                            M := [      ]
                                 [c    d]
M(1,2)=M[1,2];
                                b = b

That leads to the following,

M(x,y);
Error, unsupported type of index, x

while that worked OK for matrices,

First 8 9 10 11 12 13 14 Last Page 10 of 23