forked from mirrors/nixpkgs
34 lines
1 KiB
Nix
34 lines
1 KiB
Nix
# Operations on attribute sets.
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with {
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inherit (builtins) head tail;
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inherit (import ./default.nix) fold;
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};
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rec {
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inherit (builtins) attrNames listToAttrs hasAttr isAttrs;
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# Return an attribute from nested attribute sets. For instance ["x"
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# "y"] applied to some set e returns e.x.y, if it exists. The
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# default value is returned otherwise. !!! there is also
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# builtins.getAttr (is there a better name for this function?)
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getAttr = attrPath: default: e:
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let attr = head attrPath;
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in
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if attrPath == [] then e
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else if builtins ? hasAttr && hasAttr attr e
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then getAttr (tail attrPath) default (builtins.getAttr attr e)
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else default;
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# ordered by name
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attrValues = attrs: attrVals (__attrNames attrs) attrs;
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attrVals = nameList : attrSet :
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map (x: builtins.getAttr x attrSet) nameList;
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# iterates over a list of attributes collecting the attribute attr if it exists
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catAttrs = attr : l : fold ( s : l : if (hasAttr attr s) then [(builtins.getAttr attr s)] ++ l else l) [] l;
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} |