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Nov 22, 2011, 5:50:07 PM11/22/11

to sage-support

Hi!

I'm trying to get a matrix over SR to be callable, much like vectors

are. My code consists of the following:

"

(theta,beta,gamma)=var('theta,beta,gamma')

R_theta=matrix(SR,[[cos(theta),sin(theta),0],[-sin(theta),cos(theta),

0],[0,0,1]])

R_beta=matrix(SR,3,3,[cos(beta),0,-sin(beta),0,1,0,sin(beta),

0,cos(beta)])

"

Defining the matrices with a place for the variables yields an error

with mutiplication:

"

R_theta(theta)=matrix(SR,[[cos(theta),sin(theta),0],[-

sin(theta),cos(theta),0],[0,0,1]])

R_beta(beta)=matrix(SR,3,3,[cos(beta),0,-sin(beta),0,1,0,sin(beta),

0,cos(beta)])

R_theta*T_beta

Traceback (most recent call last):

File "<stdin>", line 1, in <module>

File "_sage_input_89.py", line 10, in <module>

exec compile(u'open("___code___.py","w").write("# -*- coding:

utf-8 -*-\\n" +

_support_.preparse_worksheet_cell(base64.b64decode("Ul90aGV0YSpSX2JldGE="),globals())

+"\\n"); execfile(os.path.abspath("___code___.py"))

File "", line 1, in <module>

File "/private/var/folders/bM/bMOEaVgXE3CHfi1Ua6Udb++++TI/-Tmp-/

tmpNfeDiM/___code___.py", line 2, in <module>

exec compile(u'R_theta*R_beta

File "", line 1, in <module>

File "element.pyx", line 1459, in

sage.structure.element.RingElement.__mul__ (sage/structure/element.c:

12096)

File "coerce.pyx", line 714, in

sage.structure.coerce.CoercionModel_cache_maps.bin_op (sage/structure/

coerce.c:6436)

File "element.pyx", line 1454, in

sage.structure.element.RingElement.__mul__ (sage/structure/element.c:

12005)

File "expression.pyx", line 2216, in

sage.symbolic.expression.Expression._mul_ (sage/symbolic/

expression.cpp:11504)

ArithmeticError: Number_T::hash() python function (__hash__) raised

exception

"

In either case, I can't get sage to substitue the variable in the

matrix. (I can define the variables before defining the matrix, but

that is redundant) Any ideas?

Thanks a lot!

Thanks a lot!

Nov 23, 2011, 3:20:06 AM11/23/11

to sage-support

Maybe:

sage:def R_theta(theta):

return matrix(SR,[[cos(theta),sin(theta),0],[-sin(theta),cos(theta),

0],[0,0,1]])

sage: R_theta(x)

[ cos(x) sin(x) 0]

[-sin(x) cos(x) 0]

[ 0 0 1]

sage: R_theta(1)

[ cos(1) sin(1) 0]

[-sin(1) cos(1) 0]

[ 0 0 1]

sage: R_theta

<function R_theta at 0x5e83848>

Andrzej Chrzeszczyk

Nov 23, 2011, 3:32:53 AM11/23/11

to sage-s...@googlegroups.com

This is a little on the terse side, but it works quite generally.

def MatrixCallable(M):

N = Matrix(SR,M)

def m(*a,**k):

return Matrix([[e(*a,**k) for e in row] for row in N])

return m

sage: x = var('x')

sage: M = [[sin(x),cos(x),0],[cos(x),sin(x),x^3]]

sage: N = MatrixCallable(M)

sage: N(x=pi/4)

[1/2*sqrt(3) 1/2 0]

[ 1/2 1/2*sqrt(3) 1/27*pi^3]

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Nov 23, 2011, 7:12:40 AM11/23/11

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On 11/23/11 1:32 AM, Tom Boothby wrote:

> This is a little on the terse side, but it works quite generally.

> This is a little on the terse side, but it works quite generally.

And it isn't quite the same as Callable symbolic expressions. I.e., if

you have two variables, you can't specify the order when you create the

matrix.

On the other hand, doing something like

sage: var('x,y')

(x, y)

sage:

M=matrix(CallableSymbolicExpressionRing((x,y)),[[x+2*y,sin(x),cos(y)],[x,y,x^2+y]])

sage: M(1,2)

[ 5 sin(1) cos(2)]

[ 1 2 3]

Really behaves like a callable expression. It prints sort of ugly, though:

sage: M

[(x, y) |--> x + 2*y (x, y) |--> sin(x) (x, y) |--> cos(y)]

[ (x, y) |--> x (x, y) |--> y (x, y) |--> x^2 + y]

That could be improved, e.g., see the printing for vectors over callable

symbolic rings, which print the arguments outside of the vector:

sage: M[0]

(x, y) |--> (x + 2*y, sin(x), cos(y))

Note that the syntax f(x,y)=... is preparsed as:

sage: preparse('f(x,y)=[[x^2,y],[x,y]]')

'__tmp__=var("x,y"); f =

symbolic_expression([[x**Integer(2),y],[x,y]]).function(x,y)'

so really all that is needed is changing the symbolic_expression

function to create a symbolic matrix if a list of lists (or tuples) is

given, and then adding a .function() method to a symbolic matrix to give

a matrix with base ring CallableSymbolicExpressionRing (as above).

Bonus points if you make those matrices print out with the arguments

first, instead of having the arguments inside of each element. I've

done this for vectors [1], so that could be a pattern for what to do here.

Thanks,

Jason

[1] See the symbolic_expression code, which has this case:

elif isinstance(x, (tuple,list)):

return vector(SR,x)

Nov 23, 2011, 11:19:48 AM11/23/11

to sage-s...@googlegroups.com

I'm a physics guy, so programing is not at the top of the to-do list for me (yet), but I might take it on, since I've been meaning to learn python as a primer for programming in general. Also, I use sage over all the other software they have at school, and sometimes bugs in sage keep me too busy. Getting to know it's innards might help those situations out.

Thanks!

Nov 23, 2011, 11:38:20 AM11/23/11

to sage-s...@googlegroups.com

On 11/23/11 9:19 AM, jrodr...@gmail.com wrote:

> I'm a physics guy, so programing is not at the top of the to-do list for me (yet), but I might take it on, since I've been meaning to learn python as a primer for programming in general. Also, I use sage over all the other software they have at school, and sometimes bugs in sage keep me too busy. Getting to know it's innards might help those situations out.

>

> I'm a physics guy, so programing is not at the top of the to-do list for me (yet), but I might take it on, since I've been meaning to learn python as a primer for programming in general. Also, I use sage over all the other software they have at school, and sometimes bugs in sage keep me too busy. Getting to know it's innards might help those situations out.

>

I think this would be a good project for a person wanting to learn more

about how to do Sage development. The modifications to

symbolic_expression should be easy (check for a nested list/tuple

structure). Then you would need to make a new function() method, in

$SAGE_ROOT/devel/sage/sage/matrix/matrix2.pyx probably, that would

create a corresponding matrix over the CallableSymbolicRing. You can

see an example for vectors in

$SAGE_ROOT/devel/sage/sage/modules/free_module.pyx (look for "def

function" in that file).

Then if you are ambitious, create a new matrix subclass for callable

symbolic expressions that mirrors what

$SAGE_ROOT/devel/sage/sage/modules/vector_callable_symbolic_dense.py

does for vectors (i.e., changes the printing).

Thanks,

Jason

Nov 23, 2011, 12:52:48 PM11/23/11

to sage-support

This is now http://trac.sagemath.org/sage_trac/ticket/12075.

On Nov 23, 11:38 am, Jason Grout <jason-s...@creativetrax.com> wrote:

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