In contrast to a theorem prover , a proof-assistant cannot find proofs on its own. In Yarrow you can experiment with various pure type systems, representing different logics and programming languages. Experience with similar proof-assistants can be useful. There are three extensions of PTSs implemented in Yarrow. First, we have definitions.
Definitions are indispensable for any practical use of PTSs.
Second, we have subtyping. Subtyping makes the type system more flexible. In particular, it can be used with records to allow formalization of Object-Oriented Programming to a certain degree. Third, we have records. Records are useful for defining programs in a PTS, in particular Object-Oriented programs.