implement std functions from nixpkgs.lib

nib/std/attrs.nix

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+rec {
+  nameValuePair = name: value: {inherit name value;};
+
+  listToAttrsIdentity = values:
+    builtins.listToAttrs (
+      builtins.map
+      (x: nameValuePair x x)
+      values
+    );
+
+  /**
+  Generate an attribute set by mapping a function over a list of
+  attribute names.
+
+  # Inputs
+
+  `names`
+
+  : Names of values in the resulting attribute set.
+
+  `f`
+
+  : A function, given the name of the attribute, returns the attribute's value.
+
+  # Type
+
+  ```
+  genAttrs :: [ String ] -> (String -> Any) -> AttrSet
+  ```
+
+  # Examples
+  :::{.example}
+  ## `lib.attrsets.genAttrs` usage example
+
+  ```nix
+  genAttrs [ "foo" "bar" ] (name: "x_" + name)
+  => { foo = "x_foo"; bar = "x_bar"; }
+  ```
+
+  :::
+  */
+  genAttrs = names: f: genAttrs' names (n: nameValuePair n (f n));
+
+  /**
+  Like `genAttrs`, but allows the name of each attribute to be specified in addition to the value.
+  The applied function should return both the new name and value as a `nameValuePair`.
+  ::: {.warning}
+  In case of attribute name collision the first entry determines the value,
+  all subsequent conflicting entries for the same name are silently ignored.
+  :::
+
+  # Inputs
+
+  `xs`
+
+  : A list of strings `s` used as generator.
+
+  `f`
+
+  : A function, given a string `s` from the list `xs`, returns a new `nameValuePair`.
+
+  # Type
+
+  ```
+  genAttrs' :: [ Any ] -> (Any -> { name :: String; value :: Any; }) -> AttrSet
+  ```
+
+  # Examples
+  :::{.example}
+  ## `lib.attrsets.genAttrs'` usage example
+
+  ```nix
+  genAttrs' [ "foo" "bar" ] (s: nameValuePair ("x_" + s) ("y_" + s))
+  => { x_foo = "y_foo"; x_bar = "y_bar"; }
+  ```
+
+  :::
+  */
+  genAttrs' = xs: f: builtins.listToAttrs (map f xs);
+}

nib/std/default.nix

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+builtins.listToAttrs [
+  (import ./attrs.nix)
+  (import ./lists.nix)
+]

nib/std/lists.nix

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+rec {
+  foldl = op: nul: list: let
+    foldl' = n:
+      if n == -1
+      then nul
+      else op (foldl' (n - 1)) (builtins.elemAt list n);
+  in
+    foldl' (builtins.length list - 1);
+
+  crossLists = f: foldl (fs: args: builtins.concatMap (f: map f args) fs) [f];
+}