commit 87b4a91fc4145e04ca028c08754bd144b8d1d02d · pyrox.dev/nixpkgs

+5 -3

lib/default.nix

···

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        */

     

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       let

     

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         # trivial, often used functions

     

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         trivial = import ./trivial.nix;

     

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         # datatypes

     

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         attrsets = import ./attrsets.nix;

     
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         filesystem = import ./filesystem.nix;

     

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       in

     

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         { inherit trivial

     

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                   attrsets lists strings stringsWithDeps

     

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                   customisation maintainers meta sources

     

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                   modules options types

     
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         }

     

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         # !!! don't include everything at top-level; perhaps only the most

     

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         # commonly used functions.

     

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         // trivial // lists // strings // stringsWithDeps // attrsets // sources

     

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         // options // types // meta // debug // misc // modules

     

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         // customisation

···

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        */

     

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       let

     

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         # often used, or depending on very little

     

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         trivial = import ./trivial.nix;

     

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         fixedPoints = import ./fixed-points.nix;

     

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         # datatypes

     

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         attrsets = import ./attrsets.nix;

     
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         filesystem = import ./filesystem.nix;

     

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       in

     

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         { inherit trivial fixedPoints

     

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                   attrsets lists strings stringsWithDeps

     

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                   customisation maintainers meta sources

     

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                   modules options types

     
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         }

     

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         # !!! don't include everything at top-level; perhaps only the most

     

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         # commonly used functions.

     

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         // trivial // fixedPoints

     

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         // lists // strings // stringsWithDeps // attrsets // sources

     

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         // options // types // meta // debug // misc // modules

     

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         // customisation

+78

lib/fixed-points.nix

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       rec {

     

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         # Compute the fixed point of the given function `f`, which is usually an

     

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         # attribute set that expects its final, non-recursive representation as an

     

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         # argument:

     

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         #

     

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         #     f = self: { foo = "foo"; bar = "bar"; foobar = self.foo + self.bar; }

     

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         #

     

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         # Nix evaluates this recursion until all references to `self` have been

     

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         # resolved. At that point, the final result is returned and `f x = x` holds:

     

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         #

     

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         #     nix-repl> fix f

     

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         #     { bar = "bar"; foo = "foo"; foobar = "foobar"; }

     

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         #

     

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         #  Type: fix :: (a -> a) -> a

     

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         #

     

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         # See https://en.wikipedia.org/wiki/Fixed-point_combinator for further

     

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         # details.

     

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         fix = f: let x = f x; in x;

     

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         # A variant of `fix` that records the original recursive attribute set in the

     

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         # result. This is useful in combination with the `extends` function to

     

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         # implement deep overriding. See pkgs/development/haskell-modules/default.nix

     

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         # for a concrete example.

     

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         fix' = f: let x = f x // { __unfix__ = f; }; in x;

     

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         # Modify the contents of an explicitly recursive attribute set in a way that

     

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         # honors `self`-references. This is accomplished with a function

     

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         #

     

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         #     g = self: super: { foo = super.foo + " + "; }

     

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         #

     

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         # that has access to the unmodified input (`super`) as well as the final

     

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         # non-recursive representation of the attribute set (`self`). `extends`

     

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         # differs from the native `//` operator insofar as that it's applied *before*

     

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         # references to `self` are resolved:

     

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         #

     

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         #     nix-repl> fix (extends g f)

     

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         #     { bar = "bar"; foo = "foo + "; foobar = "foo + bar"; }

     

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         #

     

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         # The name of the function is inspired by object-oriented inheritance, i.e.

     

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         # think of it as an infix operator `g extends f` that mimics the syntax from

     

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         # Java. It may seem counter-intuitive to have the "base class" as the second

     

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         # argument, but it's nice this way if several uses of `extends` are cascaded.

     

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         extends = f: rattrs: self: let super = rattrs self; in super // f self super;

     

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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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         # 'super' of the second

     

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         composeExtensions =

     

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           f: g: self: super:

     

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             let fApplied = f self super;

     

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                 super' = super // fApplied;

     

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             in fApplied // g self super';

     

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         # Create an overridable, recursive attribute set. For example:

     

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         #

     

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         #     nix-repl> obj = makeExtensible (self: { })

     

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         #

     

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         #     nix-repl> obj

     

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         #     { __unfix__ = «lambda»; extend = «lambda»; }

     

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         #

     

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         #     nix-repl> obj = obj.extend (self: super: { foo = "foo"; })

     

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         #

     

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         #     nix-repl> obj

     

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         #     { __unfix__ = «lambda»; extend = «lambda»; foo = "foo"; }

     

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         #

     

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         #     nix-repl> obj = obj.extend (self: super: { foo = super.foo + " + "; bar = "bar"; foobar = self.foo + self.bar; })

     

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         #

     

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         #     nix-repl> obj

     

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         #     { __unfix__ = «lambda»; bar = "bar"; extend = «lambda»; foo = "foo + "; foobar = "foo + bar"; }

     

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         makeExtensible = makeExtensibleWithCustomName "extend";

     

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         # Same as `makeExtensible` but the name of the extending attribute is

     

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         # customized.

     

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         makeExtensibleWithCustomName = extenderName: rattrs:

     

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           fix' rattrs // {

     

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             ${extenderName} = f: makeExtensibleWithCustomName extenderName (extends f rattrs);

     

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          };

     

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       }

-78

lib/trivial.nix

···

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         */

     

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         mergeAttrs = x: y: x // y;

     

       45
        
       

     

       46
       -
       

     

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         # Compute the fixed point of the given function `f`, which is usually an

     

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         # attribute set that expects its final, non-recursive representation as an

     

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         # argument:

     

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         #

     

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         #     f = self: { foo = "foo"; bar = "bar"; foobar = self.foo + self.bar; }

     

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         #

     

       53
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         # Nix evaluates this recursion until all references to `self` have been

     

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         # resolved. At that point, the final result is returned and `f x = x` holds:

     

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         #

     

       56
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         #     nix-repl> fix f

     

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         #     { bar = "bar"; foo = "foo"; foobar = "foobar"; }

     

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         #

     

       59
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         #  Type: fix :: (a -> a) -> a

     

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         #

     

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         # See https://en.wikipedia.org/wiki/Fixed-point_combinator for further

     

       62
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         # details.

     

       63
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         fix = f: let x = f x; in x;

     

       64
       -
       

     

       65
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         # A variant of `fix` that records the original recursive attribute set in the

     

       66
       -
         # result. This is useful in combination with the `extends` function to

     

       67
       -
         # implement deep overriding. See pkgs/development/haskell-modules/default.nix

     

       68
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         # for a concrete example.

     

       69
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         fix' = f: let x = f x // { __unfix__ = f; }; in x;

     

       70
       -
       

     

       71
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         # Modify the contents of an explicitly recursive attribute set in a way that

     

       72
       -
         # honors `self`-references. This is accomplished with a function

     

       73
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         #

     

       74
       -
         #     g = self: super: { foo = super.foo + " + "; }

     

       75
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         #

     

       76
       -
         # that has access to the unmodified input (`super`) as well as the final

     

       77
       -
         # non-recursive representation of the attribute set (`self`). `extends`

     

       78
       -
         # differs from the native `//` operator insofar as that it's applied *before*

     

       79
       -
         # references to `self` are resolved:

     

       80
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         #

     

       81
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         #     nix-repl> fix (extends g f)

     

       82
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         #     { bar = "bar"; foo = "foo + "; foobar = "foo + bar"; }

     

       83
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         #

     

       84
       -
         # The name of the function is inspired by object-oriented inheritance, i.e.

     

       85
       -
         # think of it as an infix operator `g extends f` that mimics the syntax from

     

       86
       -
         # Java. It may seem counter-intuitive to have the "base class" as the second

     

       87
       -
         # argument, but it's nice this way if several uses of `extends` are cascaded.

     

       88
       -
         extends = f: rattrs: self: let super = rattrs self; in super // f self super;

     

       89
       -
       

     

       90
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         # Compose two extending functions of the type expected by 'extends'

     

       91
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         # into one where changes made in the first are available in the

     

       92
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         # 'super' of the second

     

       93
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         composeExtensions =

     

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           f: g: self: super:

     

       95
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             let fApplied = f self super;

     

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                 super' = super // fApplied;

     

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             in fApplied // g self super';

     

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         # Create an overridable, recursive attribute set. For example:

     

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         #

     

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         #     nix-repl> obj = makeExtensible (self: { })

     

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         #

     

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         #     nix-repl> obj

     

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         #     { __unfix__ = «lambda»; extend = «lambda»; }

     

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         #

     

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         #     nix-repl> obj = obj.extend (self: super: { foo = "foo"; })

     

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         #

     

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         #     nix-repl> obj

     

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         #     { __unfix__ = «lambda»; extend = «lambda»; foo = "foo"; }

     

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         #

     

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         #     nix-repl> obj = obj.extend (self: super: { foo = super.foo + " + "; bar = "bar"; foobar = self.foo + self.bar; })

     

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         #

     

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         #     nix-repl> obj

     

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         #     { __unfix__ = «lambda»; bar = "bar"; extend = «lambda»; foo = "foo + "; foobar = "foo + bar"; }

     

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         makeExtensible = makeExtensibleWithCustomName "extend";

     

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         # Same as `makeExtensible` but the name of the extending attribute is

     

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         # customized.

     

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         makeExtensibleWithCustomName = extenderName: rattrs:

     

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           fix' rattrs // {

     

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             ${extenderName} = f: makeExtensibleWithCustomName extenderName (extends f rattrs);

     

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          };

     

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         # Flip the order of the arguments of a binary function.

     

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         flip = f: a: b: f b a;

     

       126

···

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         */

     

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         mergeAttrs = x: y: x // y;

     

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         # Flip the order of the arguments of a binary function.

     

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         flip = f: a: b: f b a;

     

       48