Lean 4 fork for HoTT-compatible kernel extensions (Path types, transport, HITs). Maintained against upstream leanprover/lean4.
90462e2551
This PR provides the iterator combinator `filterMap` in a pure and monadic version and specializations `map` and `filter`. This new combinator allows to apply a function to the emitted values of a stream while filtering out certain elements. `map` should have an optimized `IteratorCollect` implementation but it turns out that this is not possible without a major refactor of `IteratorCollect`: `toArrayMapped` requires a proof that the iterator is finite. If `it.mapM f` is `Finite` but `it` is not, then such a proof does not exist. `IteratorCollect` needs to take a proof that the loop will terminate for the given monadic function `f` instead. This will not be done in this PR. |
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