infix.nix

let
  inherit (builtins) map;
  inherit ((import <nixpkgs> {}).lib) 
    fold hasSuffix stringToCharacters concatStrings any;
in rec {
  inits = fold (x: y: [[]] ++ map (z: [x] ++ z) y) [[]];
  hasInfix = i: str: any (x: hasSuffix i (concatStrings x)) (inits (stringToCharacters str));
}