[erlang-questions] Spurious '100' in array:new

Luke Bakken <>
Mon Jan 28 16:40:50 CET 2019


I left an extra 10 in my explanation, it should have read:

In your case, the ?extend macro is evaluated and the result of
(NODESIZE * LEAFSIZE) is stored in the elements field of the record.

On Mon, Jan 28, 2019 at 7:36 AM Luke Bakken <> wrote:
>
> Hi Donald -
>
> I have never used the array data type, but I assume that the 100 is an
> internal implementation detail.
>
> https://github.com/erlang/otp/blob/OTP-21.2.4/lib/stdlib/src/array.erl#L151-L160
>
> Notice that the last element in the array record is for "elements",
> which are defined immediately above the record in the source code.
> non_neg_integer() can be the sole element in your array, and is
> determined by this code:
>
> https://github.com/erlang/otp/blob/OTP-21.2.4/lib/stdlib/src/array.erl#L286-L298
>
> In your case, the ?extend macro is evaluated and the result of 10 *
> (NODESIZE * LEAFSIZE) is stored in the elements field of the record.
>
> At least, I think this is the correct reading of this code :-)
> Thanks,
> Luke


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