Implement support for custom functions in GNOME Calculator

by Garima Joshi for GNOME

GNOME calculator is the default desktop calculator application of GNOME. This project aims to add support for user-defined functions(with single as well as multiple variable support) to GNOME calculator. This will add reusability and customization to the application, making it more user friendly and saving time of the user. We also aim to support auto-completion of custom/built-in functions as user is typing in the expression for evaluation, which will make using functions a pleasant experience. We also aim to give user the capability to terminate current Expression Evaluation in case it is too expensive.