lean4-htt/src/Init/Data/List/ToArrayImpl.lean
Sebastian Ullrich 09a5b34931
feat: make private the default in module (#9044)
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.
2025-06-28 16:30:53 +00:00

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/-
Copyright (c) 2024 Lean FRO. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Henrik Böving
-/
module
prelude
public import Init.Data.List.Basic
public section
set_option linter.listVariables true -- Enforce naming conventions for `List`/`Array`/`Vector` variables.
set_option linter.indexVariables true -- Enforce naming conventions for index variables.
/--
Auxiliary definition for `List.toArray`.
`List.toArrayAux as r = r ++ as.toArray`
-/
@[inline_if_reduce]
def List.toArrayAux : List α → Array α → Array α
| nil, xs => xs
| cons a as, xs => toArrayAux as (xs.push a)
/--
Converts a `List α` into an `Array α` by repeatedly pushing elements from the list onto an empty
array. `O(|xs|)`.
Use `List.toArray` instead of calling this function directly. At runtime, this operation implements
both `List.toArray` and `Array.mk`.
-/
-- This function is exported to C, where it is called by `Array.mk`
-- (the constructor) to implement this functionality.
@[inline, match_pattern, pp_nodot, export lean_list_to_array]
def List.toArrayImpl (xs : List α) : Array α :=
xs.toArrayAux (Array.mkEmpty xs.length)