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lib.lists: undeprecate crossLists

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mapCartesianProduct's output's order relies on the iteration order of the input attrset
encouraging picking non-meaningful names or arbitrary prefixed underscores if your usecase
requires a specific order.

See this thread for examples of clunkiness required to achieve a specific ordering.
https://discourse.nixos.org/t/lib-crosslists-is-deprecated-use-lib-cartesianproductofsets-instead/41824/10
This commit is contained in:
Luna Nova
2025-03-26 18:05:55 -07:00
parent 73d0441dfe
commit d1de5d4748
1 changed files with 2 additions and 14 deletions
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lib/lists.nix
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@@ -1814,7 +1814,7 @@ rec {
=> [ "13" "14" "23" "24" ]
```
The following function call is equivalent to the one deprecated above:
If you have an attrset already, consider mapCartesianProduct:
```nix
mapCartesianProduct (x: "${toString x.a}${toString x.b}") { a = [1 2]; b = [3 4]; }
@@ -1822,19 +1822,7 @@ rec {
```
:::
*/
crossLists = warn ''
lib.crossLists is deprecated, use lib.mapCartesianProduct instead.
For example, the following function call:
nix-repl> lib.crossLists (x: y: x+y) [[1 2] [3 4]]
[ 4 5 5 6 ]
Can now be replaced by the following one:
nix-repl> lib.mapCartesianProduct ({x,y}: x+y) { x = [1 2]; y = [3 4]; }
[ 4 5 5 6 ]
'' (f: foldl (fs: args: concatMap (f: map f args) fs) [ f ]);
crossLists = f: foldl (fs: args: concatMap (f: map f args) fs) [ f ];
/**
Remove duplicate elements from the `list`. O(n^2) complexity.