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| uwiger |
 Posted: Mon Apr 02, 2007 4:49 pm |
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User
Joined: 03 Jul 2006
Posts: 604
Location: Sweden
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I'm getting a bit cross-eyed, but this has got to be a bug *somewhere*:
12> M = [{attribute,1,module,m},{attribute,1,export,[{foo,1}]}|Fs] ++ [{eof,1}].
[{attribute,1,module,m},
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| Guest |
| Posted: Tue Apr 03, 2007 8:31 am |
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Guest
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As far as I understand, The ERTS User's Guide says that you'll need two
layers of lists to represent a guard sequence.
syntax_tools still accepts the older format of guards (before semicolons
in guards were introduced), so that it can still be used for the abstract
format in old Beam files.
So as I see, there is no bug.
/Bj |
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| uwiger |
| Posted: Tue Apr 03, 2007 10:04 am |
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User
Joined: 03 Jul 2006
Posts: 604
Location: Sweden
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Maybe it's just I who don't understand how to read the
doc on abstract forms, but quoted from
http://www.erlang.org/doc/doc-5.5.4/erts-5.5.4/doc/html/part_frame.html
"If C is a function clause ( Ps ) when Gs -> B where Ps
is a pattern sequence, Gs is a guard sequence and B
is a body, then
Rep(C) = {clause,LINE,Rep(Ps),Rep(Gs),Rep(B)}.
...
A guard Gs is a nonempty sequence of guard tests G_1, ...,
G_k, and Rep(Gs) = [Rep(G_1), ..., Rep(G_k)].
...
If G is true, then Rep(G) = {atom,LINE,true}.
...
If G is an operator expression E_1 Op E_2, where
Op is a binary operator, and E_1, E_2 are guard
expressions, then
Rep(G) = {op,LINE,Op,Rep(E_1),Rep(E_2)}. "
I read this as
Rep(C) = {clause,LINE,Rep(Ps),Rep(Gs),Rep(B)}
Rep(Gs) = [Rep(G)|...]
Rep(G) = {op,LINE,Op,Rep(E_1),Rep(E_2)}|...
In other words, as if
Guard = [{op,1,'==',{integer,1,1},{var,1,'R'}}]
would actually be valid.
BR,
Ulf W
> -----Original Message-----
> From: Bjorn Gustavsson [mailto:bjorn@erix.ericsson.se]
> Sent: den 3 april 2007 10:31
> To: Ulf Wiger (TN/EAB)
> Cc: erlang-bugs@erlang.org
> Subject: Re: [erlang-bugs] compile and syntax_tools disagree
>
> As far as I understand, The ERTS User's Guide says that
> you'll need two layers of lists to represent a guard sequence.
>
> syntax_tools still accepts the older format of guards (before
> semicolons in guards were introduced), so that it can still
> be used for the abstract format in old Beam files.
>
> So as I see, there is no bug.
>
> /Bj |
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| Guest |
| Posted: Tue Apr 03, 2007 11:01 am |
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Guest
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Ulf Wiger (TN/EAB) wrote:
> Maybe it's just I who don't understand how to read the
> doc on abstract forms, but quoted from
> http://www.erlang.org/doc/doc-5.5.4/erts-5.5.4/doc/html/part_frame.html
>
> "If C is a function clause ( Ps ) when Gs -> B where Ps
> is a pattern sequence, Gs is a guard sequence and B
> is a body, then
> Rep(C) = {clause,LINE,Rep(Ps),Rep(Gs),Rep(B)}.
> ...
> A guard Gs is a nonempty sequence of guard tests G_1, ...,
> G_k, and Rep(Gs) = [Rep(G_1), ..., Rep(G_k)].
Don't miss the immediately following paragraph:
"A guard sequence Gss is a sequence of guards Gs_1; ...; Gs_k, and
Rep(Gss) = [Rep(Gs_1), ..., Rep(Gs_k)]. If the guard sequence is empty,
Rep(Gss) = []."
The description of {clause, ...} that you quote above says "Gs is a
guard sequence". It would have been more obvious if that paragraph had
used Gss instead of Gs.
/Richard
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| uwiger |
| Posted: Tue Apr 03, 2007 12:23 pm |
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User
Joined: 03 Jul 2006
Posts: 604
Location: Sweden
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I didn't miss out on it. I was trying to
keep the email short. (:
The way I read the documentation in it's current
state is that it is supposed to work as syntax_tools
does, where
[G1, G2, ...] is a conjunction of guards, and
[[G11,G12,...],[G21,G22,...],...] is a disjunction.
I have no problem with the compiler requiring
[[G]] rather than [G]. I have changed the output
of my code generator to this, since clearly -
bug or no bug - this would have been a correct
pattern.
If Rep(Gss) had been used, as you suggest, it
would indeed have been more obvious, and also
correctly described the current behaviour of
the compiler. ,-)
BR,
Ulf W
> -----Original Message-----
> From: Richard Carlsson [mailto:richardc@it.uu.se]
> Sent: den 3 april 2007 13:01
> To: Ulf Wiger (TN/EAB)
> Cc: Bjorn Gustavsson; erlang-bugs@erlang.org
> Subject: Re: [erlang-bugs] compile and syntax_tools disagree
>
> Ulf Wiger (TN/EAB) wrote:
> > Maybe it's just I who don't understand how to read the doc
> on abstract
> > forms, but quoted from
> >
> http://www.erlang.org/doc/doc-5.5.4/erts-5.5.4/doc/html/part_frame.htm
> > l
> >
> > "If C is a function clause ( Ps ) when Gs -> B where Ps is
> a pattern
> > sequence, Gs is a guard sequence and B is a body, then
> > Rep(C) = {clause,LINE,Rep(Ps),Rep(Gs),Rep(B)}.
> > ...
> > A guard Gs is a nonempty sequence of guard tests G_1, ..., G_k, and
> > Rep(Gs) = [Rep(G_1), ..., Rep(G_k)].
>
> Don't miss the immediately following paragraph:
>
> "A guard sequence Gss is a sequence of guards Gs_1; ...; Gs_k, and
> Rep(Gss) = [Rep(Gs_1), ..., Rep(Gs_k)]. If the guard sequence
> is empty,
> Rep(Gss) = []."
>
> The description of {clause, ...} that you quote above says
> "Gs is a guard sequence". It would have been more obvious if
> that paragraph had used Gss instead of Gs.
>
> /Richard
>
>
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| Guest |
| Posted: Tue Apr 03, 2007 12:41 pm |
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Guest
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We'll clarify the documentation in R11B-5.
/Bj |
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| Shemalicious |
| Posted: Tue Apr 10, 2007 2:29 pm |
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Guest
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All times are GMT
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