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erlangelixir

Max length of an Erlang/Elixir atom name?

What's the max length of an erlang/elixir atom name? I know there's a a limit on the max number of atoms, but that's also everything that pops up when I search for the max length of an atom. https://www.erlang.org/doc/efficiency_guide/advanced.html

I'm considering building atoms dynamically by concatenating them to form tree-like structures, so I can get hierarchical names for processes. The total number of unique atoms would still be bounded by code size, so I'd still be well below the atom count limit.

Solution

  • Erlang documentation says that limit of characters in atom is 255 (11.2 System Limits)

    Here is an easy way to check

    iex(4)>     Enum.reduce(0..1000, :"", fn atom_length, acc ->
...(4)>       try do
...(4)>         :"#{acc}x"
...(4)>       rescue
...(4)>         e ->
...(4)>           IO.inspect(atom_length)
...(4)>           reraise e, __STACKTRACE__
...(4)>       end
...(4)>     end)
255
** (SystemLimitError) a system limit has been reached
    :erlang.binary_to_atom("xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx", :utf8)
    (stdlib 4.1) erl_eval.erl:744: :erl_eval.do_apply/7
    (stdlib 4.1) erl_eval.erl:987: :erl_eval.try_clauses/10
    (elixir 1.13.1) lib/enum.ex:4136: Enum.reduce_range/5