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lix/doc/manual/utils.nix

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Nix
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with builtins;
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rec {
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splitLines = s: filter (x: !isList x) (split "\n" s);
concatStrings = concatStringsSep "";
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replaceStringsRec = from: to: string:
# recursively replace occurrences of `from` with `to` within `string`
# example:
# replaceStringRec "--" "-" "hello-----world"
# => "hello-world"
let
replaced = replaceStrings [ from ] [ to ] string;
in
if replaced == string then string else replaceStringsRec from to replaced;
squash = replaceStringsRec "\n\n\n" "\n\n";
trim = string:
# trim trailing spaces and squash non-leading spaces
let
trimLine = line:
let
# separate leading spaces from the rest
parts = split "(^ *)" line;
spaces = head (elemAt parts 1);
rest = elemAt parts 2;
# drop trailing spaces
body = head (split " *$" rest);
in spaces + replaceStringsRec " " " " body;
in concatStringsSep "\n" (map trimLine (splitLines string));
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# FIXME: O(n^2)
unique = foldl' (acc: e: if elem e acc then acc else acc ++ [ e ]) [];
nameValuePair = name: value: { inherit name value; };
filterAttrs = pred: set:
listToAttrs (concatMap (name: let v = set.${name}; in if pred name v then [(nameValuePair name v)] else []) (attrNames set));
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}