"Regan Heath" <regan@netwin.co.nz> wrote in message news:opsafgufky5a2sq9@digitalmars.com...
> FYI.. I think the reason this had you confused is that your C code..
>
> struct vehicle {
>   enum {
>    saloon, suv
>   } body;
> };
>
> does not mean what you think it means. The above defines an *unnamed* enum AND declares an instance of it in the struct. The D Ben posted...
>
> struct vehicle {
>   enum body_t {  //defines an enum called 'body_t'
>    saloon, suv
>   }
>   body_t body;   //creates an instance of it.
> }
>
> is a complete/correct translation of the C, whereas your translation...
>
> struct a {
>    enum b {  //defines an enum called 'b'
>      c, d
>    }
> }
>
> does not create an instance of the defined enum in your struct, which is not possible in D IIRC. The D documentation should probably outline this fact.

Sure it's possible:

struct a {
    enum b { c, d }
    b e;    // e is an instance of enum b
}

Indeed, many things I have to learn about D :)


"Regan Heath" <regan@netwin.co.nz> wrote in message news:opsafgufky5a2sq9@digitalmars.com...
> On Wed, 30 Jun 2004 20:31:00 +0100, Dan Williams <dnews@ithium.NOSPAM.net> wrote:
> > w00t! Thankyou for that... I made the change you suggested, and it worked :)
> >
> > Looking at the enum docs, I don't think this is really made very clear.
> > The
> > only mention of this is right at the bottom of the page, and it doesn't
> > stand out as something I had to do.
> >
> > Well, I was then able to find that despite the first example then
> > working,
> > the second did not. I changed 'body' to 'shape' and it ran just fine.
> > Unfortunate choice of word, then... I figured body was a keyword and
> > managed
> > to locate a list at http://www.digitalmars.com/d/lex.html
> >
> > Well, thankyou, stupid problem that, but I'm glad to have it solved :)
>
> FYI.. I think the reason this had you confused is that your C code..
>
> struct vehicle {
>   enum {
>    saloon, suv
>   } body;
> };
>
> does not mean what you think it means. The above defines an *unnamed* enum AND declares an instance of it in the struct. The D Ben posted...
>
> struct vehicle {
>   enum body_t {  //defines an enum called 'body_t'
>    saloon, suv
>   }
>   body_t body;   //creates an instance of it.
> }
>
> is a complete/correct translation of the C, whereas your translation...
>
> struct a {
>    enum b {  //defines an enum called 'b'
>      c, d
>    }
> }
>
> does not create an instance of the defined enum in your struct, which is not possible in D IIRC. The D documentation should probably outline this fact.
>
> Regan.
>
> > "Ben Hinkle" <bhinkle@mathworks.com> wrote in message news:cbv3d4$13eb$1@digitaldaemon.com...
> >>
> >> "Dan Williams" <dnews@ithium.NOSPAM.net> wrote in message news:cbv2l4$1277$1@digitaldaemon.com...
> >> > Ok, I am now quite confused, which is not good, because surely there
> >> is
> >> not
> >> > much about enums that I should be getting confused about! They are,
> > after
> >> > all, just a simple data type.
> >> >
> >> > I expanded your code to make it more like mine until I encountered
the
> >> error
> >> > again. This is the code:
> >> >
> >> > struct a {
> >> >   enum b {
> >> >     c, d
> >> >   }
> >> > }
> >> > typedef a Z;
> >> > int main() {
> >> >   Z e;
> >> >   e.b = e.b.d;
> >> >   printf("%d\n", e.b);
> >> >   return 0;
> >> > }
> >> >
> >> > ...it fails with that error that I mentioned in a previous message:
> > "e.b.
> >> is
> >> > not an lvalue". Which is weird, because I assume lvalue simply means
> >> an
> >> > assignable entity, and it certainly should be assignable? In the
sense
> >> that
> >> > I should be able to assign a value to it? Maybe that message means
> >> something
> >> > else.
> >>
> >> e.b is not an lvalue. "b" is a type name not a field name. Try
something
> >> like
> >>
> >> struct vehicle {
> >>    enum body_t {
> >>      saloon, suv
> >>    }
> >>    body_t body;
> >>  }
> >>
> >> >
> >> > Anyway, before posting I decided to make the code a bit more
> >> meaningful
> > by
> >> > giving different variable names. This is the altered code:
> >> >
> >> > struct vehicle {
> >> >   enum body {
> >> >     saloon, suv
> >> >   }
> >> > }
> >> > typedef vehicle car;
> >> > int main() {
> >> >   car myCar;
> >> >   myCar.body = myCar.body.suv;
> >> >   printf("%d\n", myCar.body);
> >> >   return 0;
> >> > }
> >> >
> >> > Now, I am pretty sure that every entity there is semantically the
> >> same,
> >> just
> >> > changed in name from 'a' to 'vehicle' for instance. But bizarrely, I
> >> get
> >> > these errors:
> >> >
> >> > line 6: { enum members } expected
> >> > line 6: Declaration expected, not 'body'
> >> > line 13: identifier expected following '.', not 'body'
> >> > line 13: identifier expected following '.', not 'body'
> >> > line 14: identifier expected following '.', not 'body'
> >> > line 17: struct member expected
> >> >
> >> > Gah! Very weird!
> >> >
> >> > Just so that you can compare, I ported the above car example BACK to
> > C++.
> >> > And guess what - it compiled and ran fine. Here it is:
> >> >
> >> > struct vehicle {
> >> >  enum {
> >> >   saloon, suv
> >> >  } body;
> >> > };
> >> > typedef struct vehicle car;
> >> > int main() {
> >> >  car myCar;
> >> >  myCar.body = suv;
> >> >  printf("%d\n", myCar.body);
> >> >  return 0;
> >> > }
> >> >
> >> > Hopefully that will give you enough to go on to work out what on
earth
> > the
> >> > problem is...
> >> >
> >> >
> >> >
> >> > "Ben Hinkle" <bhinkle@mathworks.com> wrote in message news:cbuttk$rau$1@digitaldaemon.com...
> >> > > works for me:
> >> > >
> >> > > struct a {
> >> > >   enum b {
> >> > >     c, d
> >> > >   }
> >> > >   static void foo() { printf("%d\n",b.d); }
> >> > > }
> >> > >
> >> > > int main() {
> >> > >   printf("%d\n", a.b.d);
> >> > >   a.foo();
> >> > >   return 0;
> >> > > }
> >> > >
> >> > > I guess more details about your code would be needed to figure out
> > what
> >> is
> >> > > going wrong for you.
> >> > >
> >> > > "Dan Williams" <dnews@ithium.NOSPAM.net> wrote in message news:cbus74$p04$1@digitaldaemon.com...
> >> > > > I'm porting some code from C++ to D for comparison, and I've hit
> > some
> >> > > > head-scratching with enums. Specifically, scope... although I
have
> >> > > > appropriately changed the enum definition syntax to match D, I am
> >> > getting
> >> > > > errors about undefined identifiers when I try to compile. I have
> >> > searched
> >> > > > the online material and the newsgroups, and found nothing to get
> >> me
> >> past
> >> > > > this... here is part of the code:
> >> > > >
> >> > > > struct a {
> >> > > >     enum b {
> >> > > >         c, d
> >> > > >     };
> >> > > > };
> >> > > >
> >> > > > that's a simplified segment. The problem is that later on in the
> >> C++
> >> > code,
> >> > > I
> >> > > > use c and d, but apparently they are out of scope. I've tried
> >> things
> >> > like
> >> > > > b.c etc. and a.b.c (without actually knowing *why* - sometimes I
> >> hit
> >> on
> >> > > the
> >> > > > right thing by luck and work the reason out after!) but it still
> > fails
> >> > to
> >> > > > work.
> >> > > >
> >> > > > The C++ code compiles and runs perfectly, by the way.
> >> > > >
> >> > > > Is there anything I should know about enums that is not mentioned
> >> on
> >> the
> >> > D
> >> > > > site, and that is relevant to this?
> >> > > >
> >> > > >
> >> > > >
> >> > >
> >> > >
> >> >
> >> >
> >>
> >>
> >
> >
>
>
>
> -- 
> Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/

"Walter" <newshound@digitalmars.com> wrote in message news:cbv8ft$1alf$1@digitaldaemon.com...
>
> "Dan Williams" <dnews@ithium.NOSPAM.net> wrote in message news:cbuugk$s37$1@digitaldaemon.com...
> > "Walter" <newshound@digitalmars.com> wrote in message news:cbutnq$r4s$1@digitaldaemon.com...
> > >
> > > "Dan Williams" <dnews@ithium.NOSPAM.net> wrote in message news:cbus74$p04$1@digitaldaemon.com...
> > > > I'm porting some code from C++ to D for comparison, and I've hit
some
> > > > head-scratching with enums. Specifically, scope... although I have appropriately changed the enum definition syntax to match D, I am
> > getting
> > > > errors about undefined identifiers when I try to compile. I have
> > searched
> > > > the online material and the newsgroups, and found nothing to get me
> past
> > > > this... here is part of the code:
> > > >
> > > > struct a {
> > > >     enum b {
> > > >         c, d
> > > >     };
> > > > };
> > > >
> > > > that's a simplified segment. The problem is that later on in the C++
> > code,
> > > I
> > > > use c and d, but apparently they are out of scope. I've tried things
> > like
> > > > b.c etc. and a.b.c (without actually knowing *why* - sometimes I hit
> on
> > > the
> > > > right thing by luck and work the reason out after!) but it still
fails
> > to
> > > > work.
> > > >
> > > > The C++ code compiles and runs perfectly, by the way.
> > > >
> > > > Is there anything I should know about enums that is not mentioned on
> the
> > D
> > > > site, and that is relevant to this?
> > >
> > > Enums with a tag name are scoped by that tag, so you'd reference the
c,d
> > as
> > > a.b.c and a.b.d. Enums without a tag name are in the enclosing scope,
so
> > it
> > > would be a.c and a.d.
> > >
> > >
> >
> > Thanks... I think.
> >
> > I'm still having problems. There's a union in the 'a' struct, and the members are addressed in the way that you say - but then, they were
> anyway.
> > As for the enum... I end up with this code:
> >
> > struct a {
> >     enum b {
> >         c, d
> >     };
> > };
> >
> > typedef a var;
> >
> > ...
> >
> >     var e;
> >     e.b = e.b.c;
> >
> > ...
> >
> > In C++, the code was 'e.b = c' but that gets an error of 'undefined identifier c'. The problem is, the new code not only just looks *wrong*,
> and
> > *feels* wrong, but it generates another error: 'e.b is not an lvalue', whatever that means.
>
> The code *is* wrong. b is the name of the enum, it is not a member
variable.
> Not an lvalue means it isn't a memory location that can be assigned to.
>
>

Got it solved in the end, thanks to Ben Hinkle... I simply needed to instantiate the enum:

struct a {
  enum b_t {
    c, d
  }
  b_t b;
}

typedef a var;

...

    var e;
    e.b = e.b.c;

...

The e.b = e.b.c bit was actually ok in the end!

On Wed, 30 Jun 2004 15:04:27 -0700, Walter <newshound@digitalmars.com> wrote:

>
> "Regan Heath" <regan@netwin.co.nz> wrote in message
> news:opsafgufky5a2sq9@digitalmars.com...
>> FYI.. I think the reason this had you confused is that your C code..
>>
>> struct vehicle {
>>   enum {
>>    saloon, suv
>>   } body;
>> };
>>
>> does not mean what you think it means. The above defines an *unnamed* enum
>> AND declares an instance of it in the struct. The D Ben posted...
>>
>> struct vehicle {
>>   enum body_t {  //defines an enum called 'body_t'
>>    saloon, suv
>>   }
>>   body_t body;   //creates an instance of it.
>> }
>>
>> is a complete/correct translation of the C, whereas your translation...
>>
>> struct a {
>>    enum b {  //defines an enum called 'b'
>>      c, d
>>    }
>> }
>>
>> does not create an instance of the defined enum in your struct, which is
>> not possible in D IIRC. The D documentation should probably outline this
>> fact.
>
> Sure it's possible:
>
> struct a {
>     enum b { c, d }
>     b e;    // e is an instance of enum b
> }

but this is not?

struct a {
  enum b { c,d } e;
}

correct?

that is what I mean't was not possible, I phrased it badly.

Regan.

-- 
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/

"Regan Heath" <regan@netwin.co.nz> wrote in message news:opsaflv6t15a2sq9@digitalmars.com...
> > Sure it's possible:
> >
> > struct a {
> >     enum b { c, d }
> >     b e;    // e is an instance of enum b
> > }
>
> but this is not?
>
> struct a {
>    enum b { c,d } e;
> }
>
> correct?

Yes, that won't work.

>
> that is what I mean't was not possible, I phrased it badly.
>
> Regan.
>
> -- 
> Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/

>I've tried things like
> b.c etc. and a.b.c (without actually knowing *why* - sometimes I hit on
the
> right thing by luck and work the reason out after!) but it still fails to work.

Hi Dan et'al,

Ever heard of a "gub"?

It's "b.u.g" backwards = "g.u.b"

Bug ... doesn't work and don't know why

Gug ... works, but don't know why

:-D
Lynn A.