GSoC 2020 - Week 4

Key highlights of this week’s work are:

• Fixed incorrect evaluation caused due to subfactorial in limit_seq expression

  • This was a minor bug fix. The functionality of rewriting the subfactorial term present in an expression into an equivalent term expressed in the form of factorial or gamma was added which helped resolve the issue.
    
    

• Adds cdir parameter to handle series expansions on branch cuts

  • Currently, many functions in the codebase are unable to produce correct series expansions on branch cuts. As a result, the limit evaluation takes place incorrectly for these functions when the limiting value lies on the branch cuts.

    Thus, we have decided to come up with a parameter named cdir which stands for complex direction and it indicates the direction from which the series expansion is required, thus helping us to produce the correct series expansion. Special care needs to be taken while handling series expansions on the branch points.

    Once we are finished with this work, it will be a major enhancement to the limit evaluation and series expansion capabilities of SymPy.

This marks the end of Phase-1 of the program. I learnt a lot during this one month and gained many important things from my mentors.