09a5b34931
This PR adjusts the experimental module system to make `private` the default visibility modifier in `module`s, introducing `public` as a new modifier instead. `public section` can be used to revert the default for an entire section, though this is more intended to ease gradual adoption of the new semantics such as in `Init` (and soon `Std`) where they should be replaced by a future decl-by-decl re-review of visibilities.
51 lines
1.4 KiB
Text
51 lines
1.4 KiB
Text
/-
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Copyright (c) 2025 Lean FRO, LLC. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Paul Reichert
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-/
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module
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prelude
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public import Init.Data.Iterators.Combinators.Monadic.ULift
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public section
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namespace Std.Iterators
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universe v u v' u'
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variable {α : Type u} {β : Type u}
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/--
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Transforms a step of the base iterator into a step of the `uLift` iterator.
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-/
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@[always_inline, inline]
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def Types.ULiftIterator.modifyStep (step : IterStep (Iter (α := α) β) β) :
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IterStep (Iter (α := ULiftIterator.{v} α Id Id β (fun _ => monadLift)) (ULift.{v} β))
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(ULift.{v} β) :=
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(Monadic.modifyStep (step.mapIterator Iter.toIterM)).mapIterator IterM.toIter
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/--
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Transforms an iterator with values in `β` into one with values in `ULift β`.
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Most other combinators like `map` cannot switch between universe levels. This combinators
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makes it possible to transition to a higher universe.
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**Marble diagram:**
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```
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it ---a ----b ---c --d ---⊥
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it.uLift n ---.up a----.up b---.up c--.up d---⊥
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```
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**Termination properties:**
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* `Finite`: only if the original iterator is finite
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* `Productive`: only if the original iterator is productive
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-/
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@[always_inline, inline, expose]
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def Iter.uLift (it : Iter (α := α) β) :
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Iter (α := Types.ULiftIterator.{v} α Id Id β (fun _ => monadLift)) (ULift β) :=
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(it.toIterM.uLift Id).toIter
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end Std.Iterators
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