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Merge pull request #312393 from hsjobeki/doc/lib-fixedpoints
doc: migrate lib.fixedPoints to doc-comment format
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commit
43e364791b
@ -1,6 +1,6 @@
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{ lib, ... }:
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{ lib, ... }:
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rec {
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rec {
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/*
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/**
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`fix f` computes the fixed point of the given function `f`. In other words, the return value is `x` in `x = f x`.
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`fix f` computes the fixed point of the given function `f`. In other words, the return value is `x` in `x = f x`.
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`f` must be a lazy function.
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`f` must be a lazy function.
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@ -63,27 +63,52 @@ rec {
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See [`extends`](#function-library-lib.fixedPoints.extends) for an example use case.
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See [`extends`](#function-library-lib.fixedPoints.extends) for an example use case.
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There `self` is also often called `final`.
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There `self` is also often called `final`.
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Type: fix :: (a -> a) -> a
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Example:
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# Inputs
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`f`
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: 1\. Function argument
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# Type
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```
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fix :: (a -> a) -> a
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```
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# Examples
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:::{.example}
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## `lib.fixedPoints.fix` usage example
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```nix
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fix (self: { foo = "foo"; bar = "bar"; foobar = self.foo + self.bar; })
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fix (self: { foo = "foo"; bar = "bar"; foobar = self.foo + self.bar; })
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=> { bar = "bar"; foo = "foo"; foobar = "foobar"; }
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=> { bar = "bar"; foo = "foo"; foobar = "foobar"; }
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fix (self: [ 1 2 (elemAt self 0 + elemAt self 1) ])
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fix (self: [ 1 2 (elemAt self 0 + elemAt self 1) ])
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=> [ 1 2 3 ]
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=> [ 1 2 3 ]
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```
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:::
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*/
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*/
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fix = f: let x = f x; in x;
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fix = f: let x = f x; in x;
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/*
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/**
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A variant of `fix` that records the original recursive attribute set in the
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A variant of `fix` that records the original recursive attribute set in the
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result, in an attribute named `__unfix__`.
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result, in an attribute named `__unfix__`.
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This is useful in combination with the `extends` function to
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This is useful in combination with the `extends` function to
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implement deep overriding.
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implement deep overriding.
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# Inputs
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`f`
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: 1\. Function argument
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*/
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*/
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fix' = f: let x = f x // { __unfix__ = f; }; in x;
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fix' = f: let x = f x // { __unfix__ = f; }; in x;
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/*
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/**
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Return the fixpoint that `f` converges to when called iteratively, starting
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Return the fixpoint that `f` converges to when called iteratively, starting
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with the input `x`.
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with the input `x`.
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@ -92,7 +117,22 @@ rec {
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0
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0
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```
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```
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Type: (a -> a) -> a -> a
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# Inputs
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`f`
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: 1\. Function argument
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`x`
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: 2\. Function argument
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# Type
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```
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(a -> a) -> a -> a
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```
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*/
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*/
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converge = f: x:
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converge = f: x:
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let
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let
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@ -102,7 +142,7 @@ rec {
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then x
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then x
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else converge f x';
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else converge f x';
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/*
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/**
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Extend a function using an overlay.
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Extend a function using an overlay.
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Overlays allow modifying and extending fixed-point functions, specifically ones returning attribute sets.
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Overlays allow modifying and extending fixed-point functions, specifically ones returning attribute sets.
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@ -217,12 +257,30 @@ rec {
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```
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```
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:::
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:::
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Type:
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# Inputs
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`overlay`
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: The overlay to apply to the fixed-point function
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`f`
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: The fixed-point function
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# Type
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```
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extends :: (Attrs -> Attrs -> Attrs) # The overlay to apply to the fixed-point function
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extends :: (Attrs -> Attrs -> Attrs) # The overlay to apply to the fixed-point function
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-> (Attrs -> Attrs) # A fixed-point function
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-> (Attrs -> Attrs) # A fixed-point function
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-> (Attrs -> Attrs) # The resulting fixed-point function
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-> (Attrs -> Attrs) # The resulting fixed-point function
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```
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Example:
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# Examples
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:::{.example}
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## `lib.fixedPoints.extends` usage example
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```nix
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f = final: { a = 1; b = final.a + 2; }
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f = final: { a = 1; b = final.a + 2; }
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fix f
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fix f
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@ -236,13 +294,13 @@ rec {
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fix (extends (final: prev: { c = final.a + final.b; }) f)
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fix (extends (final: prev: { c = final.a + final.b; }) f)
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=> { a = 1; b = 3; c = 4; }
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=> { a = 1; b = 3; c = 4; }
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```
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:::
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*/
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*/
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extends =
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extends =
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# The overlay to apply to the fixed-point function
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overlay:
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overlay:
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# The fixed-point function
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f:
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f:
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# Wrap with parenthesis to prevent nixdoc from rendering the `final` argument in the documentation
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# The result should be thought of as a function, the argument of that function is not an argument to `extends` itself
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# The result should be thought of as a function, the argument of that function is not an argument to `extends` itself
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(
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(
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final:
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final:
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@ -252,10 +310,29 @@ rec {
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prev // overlay final prev
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prev // overlay final prev
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);
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);
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/*
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/**
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Compose two extending functions of the type expected by 'extends'
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Compose two extending functions of the type expected by 'extends'
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into one where changes made in the first are available in the
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into one where changes made in the first are available in the
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'super' of the second
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'super' of the second
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# Inputs
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`f`
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: 1\. Function argument
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`g`
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: 2\. Function argument
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`final`
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: 3\. Function argument
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`prev`
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: 4\. Function argument
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*/
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*/
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composeExtensions =
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composeExtensions =
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f: g: final: prev:
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f: g: final: prev:
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@ -263,7 +340,7 @@ rec {
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prev' = prev // fApplied;
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prev' = prev // fApplied;
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in fApplied // g final prev';
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in fApplied // g final prev';
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/*
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/**
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Compose several extending functions of the type expected by 'extends' into
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Compose several extending functions of the type expected by 'extends' into
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one where changes made in preceding functions are made available to
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one where changes made in preceding functions are made available to
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subsequent ones.
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subsequent ones.
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@ -276,7 +353,7 @@ rec {
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composeManyExtensions =
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composeManyExtensions =
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lib.foldr (x: y: composeExtensions x y) (final: prev: {});
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lib.foldr (x: y: composeExtensions x y) (final: prev: {});
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/*
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/**
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Create an overridable, recursive attribute set. For example:
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Create an overridable, recursive attribute set. For example:
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```
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```
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@ -298,9 +375,20 @@ rec {
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*/
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*/
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makeExtensible = makeExtensibleWithCustomName "extend";
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makeExtensible = makeExtensibleWithCustomName "extend";
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/*
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/**
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Same as `makeExtensible` but the name of the extending attribute is
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Same as `makeExtensible` but the name of the extending attribute is
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customized.
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customized.
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# Inputs
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`extenderName`
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: 1\. Function argument
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`rattrs`
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: 2\. Function argument
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*/
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*/
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makeExtensibleWithCustomName = extenderName: rattrs:
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makeExtensibleWithCustomName = extenderName: rattrs:
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fix' (self: (rattrs self) // {
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fix' (self: (rattrs self) // {
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