0.4.0

This release has several new minor performance and quality-of-life improvements. Fortunately, none of them should break any existing code.

High level project changes:

• Updated CI workers to Rust 1.59.0.
• Project now uses Rust edition 2021 instead of 2018.
• We now depend on num-bigint for arbitrary precision integers. This library was chosen because it does not depend on existing C code, so it should be still possible to effortlessly compile lib-bdd to, e.g., web assembly or some other less common target without major issues. However, in the future, we may put this behind a feature flag if desired.
• We now provide Python bindings as part of the biodivine_aeon package available here. In the future, we may also release lib-bdd as a separate library. But for now it is hard to ensure compatibility between objects that are technically the same in Rust, but Python sees them as coming from different libraries. This means we cannot provide Python bindings for multiple interdependent libraries as separate projects, because the objects would be incompatible in Python. So for now we are bundling all our Rust code as part of one Python package.

API changes:

• Added Bdd::restrict and Bdd::var_restrict as convenient shortcuts for select + project operations. In the future, we may consider more performant specialized implementation of this.
• Functions Bdd::write_as_string and Bdd::read_as_string are now public.
• Added Bdd::ternary_op and Bdd::fused_ternary_op as a counterpart to Bdd::binary_op and Bdd::fused_binary_flip_op. These are particularly useful in operations where multiple conditions are involved but the result is expected to be much smaller compared to the intermediate results (or empty). So they do not provide any asymptotic gains, but can reduce the constant factor overhead in many algorithms. Typical usage example is something like repeated evaluation of x = (a & b) & !c (possibly with some variable flips), where at least two arguments change so often that pre-computing either operation does not make sense. These operations are typical for reachability queries in Boolean transition systems.
• We now support exact cardinality computation using num-bigint and Bdd::exact_cardinality. Should work the same as the existing f64 version, just precisely.