[erlang-questions] Defined macros and logical bitwise operations

[Brujo Benavides]

Hi Sergei,

	Just to be clear, your issue does not depend on the usage of macros.
	See below…

—————————————————————————————————————————————————————————
-module test.

-export [print/0].

print() ->
    io:format("NUM1: ~p~n", [2#01]),
    io:format("NUM2: ~p~n", [2#01 bsl 1]),
    io:format("NUM_BOR_PAR: ~p~n", [(2#01) bor (2#01 bsl 1)]),
    io:format("NUM_BOR_NO_PAR: ~p~n", [2#01 bor 2#01 bsl 1]),
    io:format("NUM_BAND_PAR: ~p~n", [(2#01) band (2#01 bsl 1)]),
    io:format("NUM_BAND_NO_PAR: ~p~n", [2#01 band 2#01 bsl 1]),
    io:format("NUM_BXOR_PAR: ~p~n", [(2#01) bxor (2#01 bsl 1)]),
    io:format("NUM_BXOR_NO_PAR: ~p~n", [2#01 bxor 2#01 bsl 1]),
    ok.
—————————————————————————————————————————————————————————
1> c(test).
{ok,test}
2> test:print().
NUM1: 1
NUM2: 2
NUM_BOR_PAR: 3
NUM_BOR_NO_PAR: 2
NUM_BAND_PAR: 0
NUM_BAND_NO_PAR: 2
NUM_BXOR_PAR: 3
NUM_BXOR_NO_PAR: 0
ok
—————————————————————————————————————————————————————————

Your issue is predicated entirely on the operator precedence and you can find documentation about it here:
http://erlang.org/doc/reference_manual/expressions.html#operator-precedence <http://erlang.org/doc/reference_manual/expressions.html#operator-precedence>

The important bit there is: 
+ - bor bxor bsl bsr or xor	Left associative

That means that X band Y bsl Z is not the same as (X band (Y bsl Z)) but ((X band Y) bsl Z).

Hope this helps :)

Cheers!

Brujo Benavides <http://about.me/elbrujohalcon>



> On 7 Jun 2019, at 08:03, DOBRO Sergei <chessvegas@REDACTED> wrote:
> 
> -module(test).
>  
> -export([print/0]).
>  
> -define(NUM1, 2#01).
> -define(NUM2, ?NUM1 bsl 1).
>  
> -define(NUM_BOR_PAR, (?NUM1) bor (?NUM2)).
> -define(NUM_BOR_NO_PAR, ?NUM1 bor ?NUM2).
>  
> -define(NUM_BAND_PAR, (?NUM1) band (?NUM2)).
> -define(NUM_BAND_NO_PAR, ?NUM1 band ?NUM2).
>  
> -define(NUM_BXOR_PAR, (?NUM1) bxor (?NUM2)).
> -define(NUM_BXOR_NO_PAR, ?NUM1 bxor ?NUM2).
>  
> print() ->
>     io:format("NUM1: ~p~n", [?NUM1]),
>     io:format("NUM2: ~p~n", [?NUM2]),
>     io:format("NUM_BOR_PAR: ~p~n", [?NUM_BOR_PAR]),
>     io:format("NUM_BOR_NO_PAR: ~p~n", [?NUM_BOR_NO_PAR]),
>     io:format("NUM_BAND_PAR: ~p~n", [?NUM_BAND_PAR]),
>     io:format("NUM_BAND_NO_PAR: ~p~n", [?NUM_BAND_NO_PAR]),
>     io:format("NUM_BXOR_PAR: ~p~n", [?NUM_BXOR_PAR]),
>     io:format("NUM_BXOR_NO_PAR: ~p~n", [?NUM_BXOR_NO_PAR]),
>     ok.

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