self-defined operations

[yiran-git]

Thank you for your work. I'm trying to run the package on some data and would love to get rid of the trigonometric functions. I created a new ops.txt file including only the operations I need for regression. But it seems that it only affects the brute force function, so I ended up getting regressions involving trigonometric functions. Is there a way that I could turn off the operations I don't need? Thank you. Really appreciate your work.