[erlang-questions] Baffling lists

[Stu Bailey]

I'm sure I'm missing something obvious, but here goes:

What is going on here?  Is L4 a list?  If so, why can't I reverse it?

70> L4.

[[<<"8">>,<<"7">>,<<"6">>,<<"5">>],

 [<<"4">>,<<"3">>,<<"2">>,<<"1">>]|

 0]

71> lists:reverse(L4).

** exception error: bad argument

     in function  lists:reverse/2

        called as lists:reverse(0,

                                [[<<"4">>,<<"3">>,<<"2">>,<<"1">>],

                                 [<<"8">>,<<"7">>,<<"6">>,<<"5">>]])

     in call from lists:reverse/1 (lists.erl, line 152)

72> [Head1|Rest1] = L4.

[[<<"8">>,<<"7">>,<<"6">>,<<"5">>],

 [<<"4">>,<<"3">>,<<"2">>,<<"1">>]|

 0]

73> Rest1.

[[<<"4">>,<<"3">>,<<"2">>,<<"1">>]|0]

74> lists:reverse(Rest1).

** exception error: no function clause matching
lists:reverse([[<<"4">>,<<"3">>,<<"2">>,<<"1">>]|0]) (lists.erl, line 145)

75> [Head2|Rest2] = Rest1.

[[<<"4">>,<<"3">>,<<"2">>,<<"1">>]|0]

76> Head2.

[<<"4">>,<<"3">>,<<"2">>,<<"1">>]

77> Rest2.

0

78>


In practice, the kind of structure demonstrated in L4 is being returned by
a function from another library I'm trying to use, but I'm trying to
understand what's going on in general.
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