Abhishek Kumar | 18 Dec 12:14 2014
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Expansion series,Differential equations and related projects

Hello Everyone
I am CSE 1st year undergraduate student at Indian Institute of Technology,Guwahati.I am familiar with c/c++ and particularly interested in mathematics(which is my relatively strong point for me) projects.I am interested in applying for GSoC 2015.Someone please guide me how to proceed and some project details.
Thanking You
Abhishek Kumar

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Gaurav Dhingra | 18 Dec 10:38 2014
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Problem in geometry topic using the "encloses" function in entity module

 Hi all,

I am new to Sympy (and to symbolic computations...) 
I am having problem in the Geometry topic, i am using the sympy.geometry.entity.encloses function which is as follows


In [1]  from sympy.geometry import *
                from sympy import S

In [2]  t = Triangle(Point(0, 0), Point(1, 0), Point(0, 1))   # a triangle having the vertices (0, 0), (1, 0), (0, 1)

In [3]  c1 = Circle(Point(S(1)/3, S(1)/3), S(1))                   # a circle having the center (1/3, 1/3) and radius 1, the circle "c1" somepart of it lies outside the triangle "t"

In [4]    t.encloses(c1)                                                       # which returns true
Out [4] True
  

Am i having a "bug" here or i am not understanding its use.

Thanking you 
Gaurav Dhingra(  axyd0000-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org)

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Ankit Vadehrā | 18 Dec 11:48 2014
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Tests Failing for Master Repo.

I am currently trying to check test-cases for the default symy.git repo and am currently on the most recent version.
Still, it is throwing an error. There's 1 warning for the matplotlib library being a little out-of-date, apart from that:

>>
#Rest al passed, above.
sympy/utilities/tests/test_iterables.py[36] ..........................
..........                                                        [OK]
sympy/utilities/tests/test_lambdify.py[41] ............E..............
..............                                                  [FAIL]
sympy/utilities/tests/test_module_imports.py[1] X                 [OK]
>>

___________________________ xpassed tests ____________________________
sympy/core/tests/test_wester.py: test_V12
sympy/core/tests/test_wester.py: test_T10
sympy/utilities/tests/test_module_imports.py: test_module_imports_are_direct

______________________________________________________________________
____ sympy/utilities/tests/test_lambdify.py:test_numexpr_printer _____
  File "/home/ankitvad/Github/sympy/sympy/utilities/tests/test_lambdify.py", line 181, in test_numexpr_printer
    assert f(*(1, )*nargs) is not None
  File "<string>", line 1, in <lambda>
  File "/usr/lib/python2.7/dist-packages/numexpr/necompiler.py", line 687, in evaluate
    _names_cache[expr_key] = getExprNames(ex, context)
  File "/usr/lib/python2.7/dist-packages/numexpr/necompiler.py", line 608, in getExprNames
    ex = stringToExpression(text, {}, context)
  File "/usr/lib/python2.7/dist-packages/numexpr/necompiler.py", line 231, in stringToExpression
    ex = eval(c, names)
  File "<expr>", line 1, in <module>
TypeError: 'VariableNode' object is not callable

 tests finished: 5773 passed, 137 skipped, 329 expected to fail,
3 expected to fail but passed, 1 exceptions, in 2724.40 seconds
DO *NOT* COMMIT!

Could anyone please explain where and why this might be failing ?
Since my main branch is failing, any update i make still fails and it takes a lot of time to figure out
whether my updation is causing the errors or the main-branch by default.
PS: Travis-Cl takes Hours to check a pull request.. :/

Thanks,
Ankit Vadehra

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Nalin Goel | 18 Dec 07:02 2014
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Difficulty in understanding Sympy code flow

Hi Guys, 

I am experiencing some difficulty in understanding Sympy codebase and the flow of code.

I was trying to solve issue 7827 , I know that summations.py needs an _eval_integral() function but I am not able to understand how to do so.

Please help on getting started and things that  I need to do to understand the codebase.

Nalin Goel

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Dan Buchoff | 17 Dec 18:32 2014
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A modest proposal for typed expressions

This proposal is a little far-reaching, but I think it solves some real issues with the ease of use of refine and provides a reasonable way forward for typed symbols.

The problem with refine is that:
(1) It's wordy. Assumptions on symbols are succinct and easy.
(2) It requires explicit invocation so it requires the developer to refine before simplifying and simplify can't take advantage of refinements.
(3) You must track your simplifying assumptions and since these are separate from the expression, it's too easy to refine on assumptions that later don't apply.

Introduce a new type: Guard
Guard(expr,axiom) - an expression which has meaning if the axiom is true
Expr.with(axiom) - turns an expression into a Guard based on the given axiom

This solves the problem by:
(1) still allowing assumptions attached to symbols, handling them in a sane way
(2) tracking your assumptions so they can be used while simplifying
(3) requiring you to explicitly detach an expression from its assumptions

For the simplest case, this provides typed expressions:
(x**2).with(Q.integer(x))
---> Guard(x**2, Q.integer(x))

Axioms distribute over application, so each expression only needs one set of axioms
a1.with(p1) + a2.with(p2)
---> Guard(a1 + a2, p1 & p2)

x.with(Q.positive(x)) + x.with(Q.real(x))
---> Guard(2*x,Q.positive(x) & Q.real(x))

Axioms are taken to be the current assumption context, so rewrite rules can be applied more immediately.
sqrt(x**2).with(Q.nonnegative(x))
---> Guard(x,Q.nonnegative(x))

This elegantly solves the issue of typed expressions by unifying their assumptions, possibly resulting in a contradiction (which may be implemented as a special value or a ContradictionError)
Q.positive(x)+Q.negative(x)
---> x.with(Q.positive(x) & Q.negative(x))
simplify(_)
---> Contradiction

Thoughts?

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Adrián Ashley | 15 Dec 12:16 2014
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How to run Sympy Test on a module or patch.

Hello Everyone!

I am new to unit testing. It would be great if anyone could tell me how to run sympy tests, so as to test a patch.

Thanks in advance!

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AMiT Kumar | 15 Dec 05:58 2014
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New to Sympy : Working on the Issue (No solving of Matrix Equations possible) #7379

Hi everyone,

I am Amit kumar from India, pursuing Mathematics & Computing Engineering and ofcourse with interests in Mathematics as well as Sympy.  I have a decent knowledge of Python. I would like to start contributing to sympy. I have gone through the tutorials as well as enough Documentation to start with this Issue: https://github.com/sympy/sympy/issues/7379  (No solving of Matrix Equations possible). 
I would like to know if anyone else is also working on this issue. 



Thanks!
Amit Kumar
Penultimate Year UnderGrad
Delhi Technological University
http://www.iamit.in

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Lorenzo Bercelli | 14 Dec 20:16 2014
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plotting a conic section by knowing its standard equation

hello everybody, I got a very silly question: what's the best way to plot a conic section on a plane if I have its standard equation (e.g.: x^2^+y^^2=1)? I've tried plot but it needs a univariate expression, and I haven't been able to find a method to transform the expression into f(x) = \pm sqrt(1-x^2)

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Shashank Shekhar | 14 Dec 01:32 2014
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Wish to contribute to SymPy

Hi,
    I am Shashank Shekhar ,currently in fourth semester of my undergraduate studies majoring in electronics.I am new to the open-source community and would be glad if someone could help me get started .
    I came across SymPy while looking for maths/science Python based organisations where I could be of use.I have forked your repository on github and started going through your Introduction to contributing page where I came across this mailing list .I also found your tutorial videos which are very helpful .I have recently got the hang of the basics of Python (3.x) .I am not familiar with the Git shell but have started going through their tutorials as well .
      The Maths classes I have taken at college include Differential and Integral Calculus,Vector Calculus and Algebra,Sequences and Series,Linear Algebra,Ordinary and Partial Differential Equations,Laplace Transforms .I am currently taking Numerical methods and Probability and Statistics classes .How may I be of help ?

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TUSHAR SONI | 14 Dec 08:30 2014
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Contribute to Sympy in Gsoc 2015

Hi,

I want to contribute in Sympy in next year's Gsoc2015. I know C/C++ and JS but don't know how to getting started with this project. So can anyone help me for further progress. I found its github link https://github.com/sympy/csympy but i don't know what should i do here. Please help me.

Thanks!!
Best Regards,
Tushar

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Dan Buchoff | 13 Dec 22:13 2014
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Function Composition

What's the right way to compose a multivariate polynomial with a unary polynomial in an argument other than the first?

A simple example is:
f = (x, y) ↦ x + y
g = y ↦ 2⋅y
f composed with g = (x, y) ↦ x + 2⋅y

I've tried substitution which doesn't seem to even give a valid polynomial (is a polynomial with expressions as generators even mathematically meaningful?):
>>> Poly("x+y").subs(S("y"),"y*2")
Poly(x + 2*y, x, 2*y, domain='ZZ')

I've also tried composition, but this seems to only compose in the first argument (and for some reason only works for polynomials):
>>> Poly("x+y").compose(Poly("y*2",S("y")))
Poly(3*y, x, y, domain='ZZ')

And evaluating on polynomial arguments:
>>> Poly("x+y")(Poly("x"),Poly("2*y"))
Poly(x, x, domain='ZZ') + Poly(2*y, y, domain='ZZ')

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