zero length segments!

[Bjorn Gustavsson]

It is an old bug that the shell allows some bit syntax expressions that
the compiler doesn't allow.

In the upcoming R9 release, the shell evalulator has been corrected.

/Bjorn

"Happi" <happi@REDACTED> writes:

> The bitsize can not be an arbitrary expression, just bind the size before
> the match:
> 
> t(Bit) when integer(Bit) ->
>   S = (31 - Bit),
>    <<_:S, Flag:1, _:(Bit)>> = <<1:32>>,
>    Flag.
> 
> ----- Original Message -----
> From: "Vance Shipley" <vances@REDACTED>
> To: <erlang-questions@REDACTED>
> Sent: Tuesday, September 24, 2002 4:02 PM
> Subject: Re: zero length segments!
> 
> 
> >
> > Well didn't I speak too soon!  While this works wonderfully in the shell
> > it won't complile. :(
> >
> >
> > Eshell V5.1.2  (abort with ^G)
> > 1> T = fun(Bit) -> <<_:(31 - Bit), Flag:1, _:(Bit)>> = <<1:32>>, Flag end.
> > #Fun<erl_eval.5.63972567>
> > 2> T(0).
> > 1
> > 3> T(1).
> > 0
> >
> > -module(t).
> > -export([t/1]).
> >
> > t(Bit) when integer(Bit) ->
> >    <<_:(31 - Bit), Flag:1, _:(Bit)>> = <<1:32>>,
> >    Flag.
> >
> > 1> c(t).
> > ./t.erl:5: illegal bit size
> > error
> >
> >
> > The problem seems to be with the expression (31 - Bit).
> >
> > Any idea how to get past this?
> >
> > -Vance

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