nix-helpers: ab720995d9ff2c32c9b6f134d1fc1945d6351f0d

     1: { die, getType }:
     2: 
     3: with builtins;
     4: with {
     5:   # Is xs a sublist of ys?
     6:   go = xs: ys:
     7:     assert isList xs || die {
     8:       inherit xs;
     9:       error = "First arg of subset must be list";
    10:       type = getType xs;
    11:     };
    12:     assert isList ys || die {
    13:       inherit ys;
    14:       error = "Second arg of subset must be list";
    15:       type = getType ys;
    16:     };
    17:     all (x: elem x ys) xs;
    18: };
    19: assert go [ ] [ ];
    20: assert go [ ] [ 1 2 3 ];
    21: assert go [ 2 1 ] [ 1 2 3 ];
    22: assert !(go [ 2 1 ] [ ]);
    23: assert !(go [ 2 4 ] [ 1 2 3 ]);
    24: go