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digitalmars.D - Structure property bug?

reply Todd <toddtitus mindspring.com> writes:
I'm using DFL w/DMD ver 1.020 and receive the following compile 
error's: 

no property 'Data' for type 'ARINCDATA_CELL [51u]' 
ArincWord is not an lvalue 
ReceivedChannel is not an lvalue 
Returned status code 1 

Code: 

alias uint ArincWord; 
alias uint TimeRead; 
alias short ReceivedChannel; 

struct ARINCDATA_CELL 
{ 
  align(1): 
    short Channel; 
    uint Time; 
    uint Data; 
} 
. 
. 
. 
ARINCDATA_CELL ArincData[51]; 
. 
. 
if(ArincData.Data &0xff == 203) 
{ 
  ArincWord       = ArincData[i].Data; 
  ReceivedChannel = ArincData[i].Channel; 
} 
. 
. 
. 
Tried everything I could think of but no dice. 
Think its related to the "[51]" or a bug. I've seen this error 
posted in the past, however none of the solutions seem to work, 
unless I missed one somewhere? 

Any idea's? 

Todd
Oct 04 2007
parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
"Todd" wrote

 I'm using DFL w/DMD ver 1.020 and receive the following compile
 error's:

 no property 'Data' for type 'ARINCDATA_CELL [51u]'
 ArincWord is not an lvalue
 ReceivedChannel is not an lvalue
 Returned status code 1

 Code:

 alias uint ArincWord;
 alias uint TimeRead;
 alias short ReceivedChannel;

 struct ARINCDATA_CELL
 {
  align(1):
    short Channel;
    uint Time;
    uint Data;
 }
 .
 .
 .
 ARINCDATA_CELL ArincData[51];
 .
 .
 if(ArincData.Data &0xff == 203)
 {
  ArincWord       = ArincData[i].Data;
  ReceivedChannel = ArincData[i].Channel;
 }
 .
 .
 .
 Tried everything I could think of but no dice.
 Think its related to the "[51]" or a bug. I've seen this error
 posted in the past, however none of the solutions seem to work,
 unless I missed one somewhere?

 Any idea's?


This works.  I think you have a few syntax errors:

  if(ArincData[i].Data &0xff == 203)
  {
    ArincWord v1       = ArincData[i].Data;
    ReceivedChannel v2= ArincData[i].Channel;
  }


Note the [i] in the if statement, and the variable names v1 and v2.

-Steve
Oct 04 2007
parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
"Steven Schveighoffer" wrote

  if(ArincData[i].Data &0xff == 203)


I just realized also that assuming D has the same operator precedence as 
C/C++, this really evalulates as:

if(ArincData[i].Data & (0xff == 203))

Which will obviously be compiled out.

So what you really want is:

if((ArincData[i].Data & 0xff) == 203)

BTW, I looked through the entire spec, and cannot find operator precedence 
anywhere.  Anyone know where it is?

-Steve
Oct 04 2007
next sibling parent reply Regan Heath <regan netmail.co.nz> writes:
Steven Schveighoffer wrote:

 BTW, I looked through the entire spec, and cannot find operator precedence 
 anywhere.  Anyone know where it is?


It's not ideal but you can figure out precedence by looking at:
http://www.digitalmars.com/d/expression.html

The first operator mentioned is , and it has the lowest precedence (due 
to how the syntax tree is parsed - I think).

regan
Oct 04 2007
parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
"Regan Heath" wrote

 Steven Schveighoffer wrote:

 BTW, I looked through the entire spec, and cannot find operator 
 precedence anywhere.  Anyone know where it is?


 It's not ideal but you can figure out precedence by looking at:
 http://www.digitalmars.com/d/expression.html

 The first operator mentioned is , and it has the lowest precedence (due to 
 how the syntax tree is parsed - I think).


I think you are right about this, but it is VERY subtle.  I had to read it 
for about 20 minutes before I understood what you are talking about.

It would be nice to have a table at the end, which summarizes the 
precedence.  Walter?

-Steve
Oct 04 2007
parent reply Regan Heath <regan netmail.co.nz> writes:
Steven Schveighoffer wrote:

 "Regan Heath" wrote

 Steven Schveighoffer wrote:

 BTW, I looked through the entire spec, and cannot find operator 
 precedence anywhere.  Anyone know where it is?


 It's not ideal but you can figure out precedence by looking at:
 http://www.digitalmars.com/d/expression.html

 The first operator mentioned is , and it has the lowest precedence (due to 
 how the syntax tree is parsed - I think).


 
 I think you are right about this, but it is VERY subtle.  I had to read it 
 for about 20 minutes before I understood what you are talking about.
 
 It would be nice to have a table at the end, which summarizes the 
 precedence.  Walter?


http://www.digitalmars.com/d/archives/12484.html

<g>

Regan
Oct 04 2007
parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
"Regan Heath" wrote

 http://www.digitalmars.com/d/archives/12484.html

 <g>


Hm... I guess we know Walter's opinion :)  If it's just a question of not 
having time to do the table, would it be possible for someone to write one 
and submit it for Walter to include?  Because telling someone to manually 
parse the grammar to me is like telling someone to go read the compiler code 
to figure out the precedence.  I know a lot of good coders who don't 
necessarily read language grammar specs.  Even I, who understood generally 
what the grammar spec means, didn't get that the operator precedence was 
"hidden" in the grammar.  I generally ignore the grammar boxes and just read 
the english descriptions/examples.

-Steve
Oct 04 2007
parent reply Regan Heath <regan netmail.co.nz> writes:
Steven Schveighoffer wrote:

 "Regan Heath" wrote

 http://www.digitalmars.com/d/archives/12484.html

 <g>


 
 Hm... I guess we know Walter's opinion :)  If it's just a question of not 
 having time to do the table, would it be possible for someone to write one 
 and submit it for Walter to include?  Because telling someone to manually 
 parse the grammar to me is like telling someone to go read the compiler code 
 to figure out the precedence.  I know a lot of good coders who don't 
 necessarily read language grammar specs.  Even I, who understood generally 
 what the grammar spec means, didn't get that the operator precedence was 
 "hidden" in the grammar.  I generally ignore the grammar boxes and just read 
 the english descriptions/examples.


I think that's a good idea, the most likely to see results any time 
soon.  I suspect operator precedence in D is almost identical to C/C++ 
so I'd start by copying a table for C/C++, eg.

(a quick google)
http://www.difranco.net/cop2220/op-prec.htm

Regan
Oct 04 2007
parent reply James Dennett <jdennett acm.org> writes:
Regan Heath wrote:

 Steven Schveighoffer wrote:

 "Regan Heath" wrote

 http://www.digitalmars.com/d/archives/12484.html

 <g>


 Hm... I guess we know Walter's opinion :)  If it's just a question of
 not having time to do the table, would it be possible for someone to
 write one and submit it for Walter to include?  Because telling
 someone to manually parse the grammar to me is like telling someone to
 go read the compiler code to figure out the precedence.  I know a lot
 of good coders who don't necessarily read language grammar specs. 
 Even I, who understood generally what the grammar spec means, didn't
 get that the operator precedence was "hidden" in the grammar.  I
 generally ignore the grammar boxes and just read the english
 descriptions/examples.


 
 I think that's a good idea, the most likely to see results any time
 soon.  I suspect operator precedence in D is almost identical to C/C++
 so I'd start by copying a table for C/C++, eg.
 
 (a quick google)
 http://www.difranco.net/cop2220/op-prec.htm


Operator precendence for C++ cannot be (correctly) expressed
in a linear table; a grammar is the simplest way to capture
it accurately.  (That may not be true for D, which has been
able to keep many things simpler.)

-- James
Oct 04 2007
parent "Janice Caron" <caron800 googlemail.com> writes:
On 10/5/07, James Dennett <jdennett acm.org> wrote:

 Operator precendence for C++ cannot be (correctly) expressed
 in a linear table


Ooh, now that's an interesting statement!

Why not?
Oct 05 2007
prev sibling parent Todd <toddtitus mindspring.com> writes:
Steven Schveighoffer Wrote:


 "Steven Schveighoffer" wrote

  if(ArincData[i].Data &0xff == 203)


 
 I just realized also that assuming D has the same operator precedence as 
 C/C++, this really evalulates as:
 
 if(ArincData[i].Data & (0xff == 203))
 
 Which will obviously be compiled out.
 
 So what you really want is:
 
 if((ArincData[i].Data & 0xff) == 203)
 
 BTW, I looked through the entire spec, and cannot find operator precedence 
 anywhere.  Anyone know where it is?
 
 -Steve 
 
 


Thanks Steve
That works perfect, funny how everything gets blurry at the end of the day.

Todd
Oct 04 2007