56 lines
1.4 KiB
Nix
56 lines
1.4 KiB
Nix
with builtins;
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rec {
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fold = op: nul: list:
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if list == []
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then nul
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else op (head list) (fold op nul (tail list));
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concat =
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fold (x: y: x + y) "";
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and = fold (x: y: x && y) true;
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flatten = x:
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if isList x
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then fold (x: y: (flatten x) ++ y) [] x
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else [x];
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sum = fold (x: y: add x y) 0;
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hasSuffix = ext: fileName:
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let lenFileName = stringLength fileName;
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lenExt = stringLength ext;
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in !(lessThan lenFileName lenExt) &&
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substring (sub lenFileName lenExt) lenFileName fileName == ext;
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# Split a list at the given position.
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splitAt = pos: list:
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if pos == 0 then {first = []; second = list;} else
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if list == [] then {first = []; second = [];} else
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let res = splitAt (sub pos 1) (tail list);
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in {first = [(head list)] ++ res.first; second = res.second;};
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# Stable merge sort.
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sortBy = comp: list:
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if lessThan 1 (length list)
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then
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let
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split = splitAt (div (length list) 2) list;
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first = sortBy comp split.first;
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second = sortBy comp split.second;
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in mergeLists comp first second
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else list;
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mergeLists = comp: list1: list2:
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if list1 == [] then list2 else
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if list2 == [] then list1 else
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if comp (head list2) (head list1) then [(head list2)] ++ mergeLists comp list1 (tail list2) else
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[(head list1)] ++ mergeLists comp (tail list1) list2;
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id = x: x;
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const = x: y: x;
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}
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