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binaryerlangpattern-matchingbitstring

Erlang 0 bitstring pattern matching

How do you pattern match a bitstring that equals 0 in erlang? In other words patterns of the form:

<<0:17>>
<<0:1>>
<<0:N>>

This is for defining a function.

Thanks

Solution

  • Here is a workaround, I hope it helps:

    -module(lab).
-compile(export_all).

is_zero_bitstring(BitString) ->
    Size = erlang:bit_size(BitString),
    <<0:Size>> =:= BitString.

    Run it from within the Erlang shell:

    1> c(lab).
{ok,lab}
2> lab:is_zero_bitstring(<<0:17>>).
true
3> lab:is_zero_bitstring(<<0:1>>). 
true
4> lab:is_zero_bitstring(<<0:123456>>).  
true
5> lab:is_zero_bitstring(<<7>>).   
false