From looking at the description of associative arrays, it looks like I should be able to say:

struct A {
  int a;
}

int main()
{
  A[char[]] x;
  x["a"].a = 1;  // causes a runtime error
  return( 0 );
}

But, when compiled and run with 0.128, this generates:
  Error: ArrayBoundsError z.d(8)

On Wed, 20 Jul 2005 18:57:53 -0400, Steve Adams wrote:

>  From looking at the description of associative arrays, it looks like I
> should be able to say:
> 
> struct A {
>    int a;
> }
> 
> int main()
> {
>    A[char[]] x;
>    x["a"].a = 1;  // causes a runtime error
>    return( 0 );
> }
> 
> But, when compiled and run with 0.128, this generates:
>    Error: ArrayBoundsError z.d(8)

You get this because there is no x["a"] in existence yet. Try this ...


 struct A {
    int a;
 }

 int main()
 {
    A[char[]] x;
    x["a"] = *(new A); // Create an instance of the struct.
    x["a"].a = 1;
    return( 0 );
 }

-- 
Derek
Melbourne, Australia
21/07/2005 9:11:22 AM

Thanks, that did it.

wrote:

> On Wed, 20 Jul 2005 18:57:53 -0400, Steve Adams wrote:
> 
> 
>> From looking at the description of associative arrays, it looks like I 
>>should be able to say:
>>
>>struct A {
>>   int a;
>>}
>>
>>int main()
>>{
>>   A[char[]] x;
>>   x["a"].a = 1;  // causes a runtime error
>>   return( 0 );
>>}
>>
>>But, when compiled and run with 0.128, this generates:
>>   Error: ArrayBoundsError z.d(8)
> 
> 
> You get this because there is no x["a"] in existence yet. Try this ...
> 
> 
>  struct A {
>     int a;
>  }
>   int main()
>  {
>     A[char[]] x;
>     x["a"] = *(new A); // Create an instance of the struct.
>     x["a"].a = 1;     return( 0 );
>  }
> 

> int main()
> {
>    A[char[]] x;
>    x["a"] = *(new A); // Create an instance of the struct.
>    x["a"].a = 1;
>    return( 0 );
> }

Note the *(new A) will allocate a new A and then copy the contents to x["a"]
and then throw away the allocated memory. So a way of doing the same thing
without allocating extra memory is to
 x["a"] = A.init;

On Wed, 20 Jul 2005 20:46:26 -0400, Ben Hinkle wrote:

>> int main()
>> {
>>    A[char[]] x;
>>    x["a"] = *(new A); // Create an instance of the struct.
>>    x["a"].a = 1;
>>    return( 0 );
>> }
> 
> Note the *(new A) will allocate a new A and then copy the contents to x["a"]
> and then throw away the allocated memory. So a way of doing the same thing
> without allocating extra memory is to
>  x["a"] = A.init;

That's neat. Thanks.

-- 
Derek
Melbourne, Australia
21/07/2005 10:49:46 AM

Ben, thanks for this wanderfull hint! :)
-- 
...........
Dejan Lekic
  http://dejan.lekic.org

Ben Hinkle says...
>
>> int main()
>> {
>>    A[char[]] x;
>>    x["a"] = *(new A); // Create an instance of the struct.
>>    x["a"].a = 1;
>>    return( 0 );
>> }
>
>Note the *(new A) will allocate a new A and then copy the contents to x["a"] and then throw away the allocated memory. So a way of doing the same thing without allocating extra memory is to
> x["a"] = A.init;

Ben,

this is not working for me.  However, new is.  Take this example:

import std.stdio;
class ReportTotals
{
char[] DayDate = "";
int PPHArr[23];
int FPHArr[23];
}
void main()
{
ReportTotals Month[];
Month.length = Month.length + 1;
//Month[0] = ReportTotals.init;
Month[0] = new ReportTotals();
Month[0].DayDate = "Apr 6";
}

if you compile this program, it works.  However, if you comment out the "new" line with your suggested .init like, I get an access violation.  Why is that?  I want to save memory, but I also want it to work. ;-)

thanks for the help.

josé

On Fri, 22 Jul 2005 04:55:13 +0000 (UTC), jicman wrote:

> Ben Hinkle says...
>>
>>> int main()
>>> {
>>>    A[char[]] x;
>>>    x["a"] = *(new A); // Create an instance of the struct.
>>>    x["a"].a = 1;
>>>    return( 0 );
>>> }
>>
>>Note the *(new A) will allocate a new A and then copy the contents to x["a"] and then throw away the allocated memory. So a way of doing the same thing without allocating extra memory is to
>> x["a"] = A.init;
> 
> Ben,
> 
> this is not working for me.  However, new is.  Take this example:
> 
> import std.stdio;
> class ReportTotals
> {
> char[] DayDate = "";
> int PPHArr[23];
> int FPHArr[23];
> }
> void main()
> {
> ReportTotals Month[];
> Month.length = Month.length + 1;
> //Month[0] = ReportTotals.init;
> Month[0] = new ReportTotals();
> Month[0].DayDate = "Apr 6";
> }
> 
> if you compile this program, it works.  However, if you comment out the "new" line with your suggested .init like, I get an access violation.  Why is that?  I want to save memory, but I also want it to work. ;-)
> 
> thanks for the help.
> 
> josé

Because the .init technique was for use with structs and other value-types and not with classes.

Structs and Classes do not share the same syntax in D, which makes template writing such a PIA.

For structs one would use '*(new Foo)' but for classes one uses 'new Foo'.
Yucky, no?

-- 
Derek
Melbourne, Australia
22/07/2005 4:34:24 PM

Derek Parnell says...
>
>On Fri, 22 Jul 2005 04:55:13 +0000 (UTC), jicman wrote:
>
>> Ben Hinkle says...
>>>
>>>> int main()
>>>> {
>>>>    A[char[]] x;
>>>>    x["a"] = *(new A); // Create an instance of the struct.
>>>>    x["a"].a = 1;
>>>>    return( 0 );
>>>> }
>>>
>>>Note the *(new A) will allocate a new A and then copy the contents to x["a"] and then throw away the allocated memory. So a way of doing the same thing without allocating extra memory is to
>>> x["a"] = A.init;
>> 
>> Ben,
>> 
>> this is not working for me.  However, new is.  Take this example:
>> 
>> import std.stdio;
>> class ReportTotals
>> {
>> char[] DayDate = "";
>> int PPHArr[23];
>> int FPHArr[23];
>> }
>> void main()
>> {
>> ReportTotals Month[];
>> Month.length = Month.length + 1;
>> //Month[0] = ReportTotals.init;
>> Month[0] = new ReportTotals();
>> Month[0].DayDate = "Apr 6";
>> }
>> 
>> if you compile this program, it works.  However, if you comment out the "new" line with your suggested .init like, I get an access violation.  Why is that?  I want to save memory, but I also want it to work. ;-)
>> 
>> thanks for the help.
>> 
>> josé
>
>Because the .init technique was for use with structs and other value-types and not with classes.

Aaaaah...  It would seem to me that classes should also use it.

>Structs and Classes do not share the same syntax in D, which makes template writing such a PIA.
That's why I was never able to get a struct working. ;-)  But Classes worked
right away with "new Blah();".


>For structs one would use '*(new Foo)' but for classes one uses 'new Foo'.
>Yucky, no?

Indeed.  I would have set them the same.  But I still love D.  I guess no language can be perfect. :-)

thanks for the explanation.

josé

On Wed, 20 Jul 2005 20:46:26 -0400, "Ben Hinkle" <ben.hinkle@gmail.com> wrote:

>> int main()
>> {
>>    A[char[]] x;
>>    x["a"] = *(new A); // Create an instance of the struct.
>>    x["a"].a = 1;
>>    return( 0 );
>> }
>
>Note the *(new A) will allocate a new A and then copy the contents to x["a"] and then throw away the allocated memory. So a way of doing the same thing without allocating extra memory is to
> x["a"] = A.init;

What is the concise method of initializing the members of my array of structs? It seems long-handed to do this:

x["a"].a = 1;
x["a"].b = 2;
etc.

Can this be shortened? According to spec_DMD_0.109.pdf, pages 100-101, I *think* I should be able to do something like this:

x["a"] = {a:1, b:2};

But the compiler gives me the following error: "expression expected,
not '{'". I also tried replacing {} with () and got "found ':' when
expecting ')'".

Thank you.
--
On the Internet, no one knows you're [using] a VIC-20.