What's Changed
* Custom complexities for operators, constants, and variables (https://github.com/MilesCranmer/PySR/pull/138)
* Early stopping conditions (https://github.com/MilesCranmer/PySR/pull/134)
* Based on a certain loss value being achieved
* Max number of evaluations (for theoretical studies of genetic algorithms, rather than anything practical).
* Work with specified expression rather than the one given by `model_selection`, by passing `index` to the function you wish to use (e.g,. `model.predict(X, index=5)` would use the 5th equation.).
**Full Changelog since v0.8.1**: https://github.com/MilesCranmer/PySR/compare/v0.8.1...v0.8.5