Re: [sympy] Some queries regarding the Quaternions feature I wish to contribute

[Aaron Meurer]

On Fri, Sep 8, 2017 at 6:24 AM, Nikhil Pappu <nkhl...@gmail.com> wrote:

I wrote a Quaternion class which provides basic quaternion operations (please see the attachment).

I have never made an open source contribution before so I am sorry if any of these questions are stupid.

Here are my queries :

1) What module of sympy should I put this file in?

I'm not sure what the best place is. I would look at all the submodules and put it where it fits best for the intended use case. Maybe it needs a new submodule. If you can't find a good place for it, just put it in sympy/functions for now.

 

2) Is my code good enough to be added to sympy? If not, what changes should I make?

Please open a pull request. It is much easier to suggest changes on GitHub.

 

3) printing issue :

In my code I used 2 classes for printing (CustomStrPrinter and CustomLatexPrinter) and set the default to CustomStrPrinter.

The issue is that if I set the default to CustomLatexPrinter it works fine for IPython shell commands but when I call the print function on expressions

it prints the latex form of the expression.

I want shell commands to use the CustomLatexPrinter (if latex is available) and print statements to use the CustomStrPrinter.

I guess I am confused about this whole printing thing.

In short, I want the printing to work in the way it works for sympy matrices (gives a fancy latex matrix in IPython shell commands but gives a normal string when print is used).

If you want to modify the default printers you need to define the appropriate method on the object, like _latex and _sympystr. See http://docs.sympy.org/latest/modules/printing.html.

4) I made some functions in the code called diff, integrate, exp and ln and they can be called on a Quaternion object q as

q.integrate()

q.exp()

q.ln()

but I also want them to work when sympy.integrate(q), sympy.exp(q), sympy.ln(q) are used. How should I accomplish this? 

For integrate() you should define _eval_integral. For exp() I believe _eval_power will work. For other functions such as ln, there's not currently a way to define the behavior. How do you define the exponential and logarithm of a quaternion by the way?

Aaron Meurer

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[Nikhil Pappu]

Thanks for the reply Aaron.
I found info on exp, ln and power of quaternions on the Wikipedia page.
https://en.m.wikipedia.org/wiki/Quaternion