{ lib, ... }:
with lib;
with builtins; rec {
  readLines = f: let lines = filter isString (split "\n" (readFile f)); in take ((length lines) - 1) lines;
  splitWhitespace = s: filter isString (builtins.split "[[:space:]]+" s);
  abs = i: if i >= 0 then i else i * -1;
  delta = x: y: abs (x - y);
  listSum = foldl' add 0;
  eq = x: y: x == y;
}