Re: Concerns about using struct initializer in UDA?
On Friday, 12 May 2017 at 19:33:52 UTC, ag0aep6g wrote:
On 05/12/2017 09:01 PM, Andre Pany wrote:
[...]
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You can create the attribute separately:
enum Field a = { locationName: "B" };
@a int c;
Or if avoiding the extra symbol is more important than beauty,
call a function literal:
@((){ Field a = { locationName: "B" }; return a; }()) int c;
That's not as succinct as the syntax you propose, of course.
But your syntax (`@A = {locationName: "B"} int c;`) misses an
important detail: There's no indication what the type of the
attribute is (or is `A` supposed to be the type?). To make it
work, you will have to add that. Something like
`@Field(locationName: "B")` or `@Field{locationName: "B"}` or
whatever works.
At that point, why limit it to attributes? Constructors like
that would be nice everywhere. I remember such syntax being
discussed repeatedly, but I don't know where we stand. Maybe
there's a DIP already?
Yes, A is supposed to be the type. I have included the equal sign
to to match the existing struct initializer as far as possible.
I would like to limit the dip to increase the chances the dip is
accepted.
Kind regards
André
Re: Concerns about using struct initializer in UDA?
On 05/12/2017 09:01 PM, Andre Pany wrote:
On Friday, 12 May 2017 at 10:23:34 UTC, Nicholas Wilson wrote:
[...]
I'm not sure if it isi what you're looking for but you can do
struct Field
{
string location;
string locationName;
}
struct Foo
{
@Field("","B") int c;
}
[...]
I think there are cases where this syntax is more readable and there are
cases where struct initialization is more readable. In the example you
gave, I do not know what is the second field about and having to mention
the first field feels like a burden. As developer I want the choice to
decide between these 2 syntax options.
You can create the attribute separately:
enum Field a = { locationName: "B" };
@a int c;
Or if avoiding the extra symbol is more important than beauty, call a
function literal:
@((){ Field a = { locationName: "B" }; return a; }()) int c;
That's not as succinct as the syntax you propose, of course.
But your syntax (`@A = {locationName: "B"} int c;`) misses an important
detail: There's no indication what the type of the attribute is (or is
`A` supposed to be the type?). To make it work, you will have to add
that. Something like `@Field(locationName: "B")` or
`@Field{locationName: "B"}` or whatever works.
At that point, why limit it to attributes? Constructors like that would
be nice everywhere. I remember such syntax being discussed repeatedly,
but I don't know where we stand. Maybe there's a DIP already?
Re: Concerns about using struct initializer in UDA?
On Friday, 12 May 2017 at 10:25:07 UTC, Seb wrote: On Friday, 12 May 2017 at 10:13:02 UTC, Andre Pany wrote: Does it make sense to open a DIP? It would make UDA quite nice to use if you can group several attributes into a struct. Or someone know whether there are already known issues why it isn't possible? The entire point of a DIP is to do this research for everyone and summarize it an easy-to-access and easy-to-find fashion ;-) FWIW there is an abandoned DIP for in-place struct initialization (https://github.com/dlang/DIPs/pull/22) - it might make sense to invest the effort to revive it from the dead... If I find time I will create a new dip. The dip you mentioned is about a different usage scenario. My proposal is only about sructures used as UDA. As far as I remember the old dip was not possible due to comma syntax which is now in deprecation phase. Kund regards André
Re: Concerns about using struct initializer in UDA?
On Friday, 12 May 2017 at 10:23:34 UTC, Nicholas Wilson wrote:
On Thursday, 11 May 2017 at 10:49:58 UTC, Andre Pany wrote:
Hi,
I know there are concerns about struct initialization in
method calls but what is about struct initializer in UDA?
Scenario: I want to set several UDA values. At the moment I
have to create for each value a structure with exactly 1
field. But it would be quite nice if I could use struct
initialization to group these values:
struct Field
{
string location;
string locationName;
}
struct Foo
{
@A = {locationName: "B"} int c; // <--
}
void main() {}
Of course the syntax is questionable, it is just a proposal.
What do you think?
Kind regards
André
I'm not sure if it isi what you're looking for but you can do
struct Field
{
string location;
string locationName;
}
struct Foo
{
@Field("","B") int c;
}
We use this for our compiler recognised attributes in LDC, see
llvmAttr for an example
(https://github.com/ldc-developers/druntime/blob/ldc/src/ldc/attributes.d#L108)
I think there are cases where this syntax is more readable and
there are cases where struct initialization is more readable. In
the example you gave, I do not know what is the second field
about and having to mention the first field feels like a burden.
As developer I want the choice to decide between these 2 syntax
options.
Kind regards
André
Re: Concerns about using struct initializer in UDA?
On Friday, 12 May 2017 at 10:13:02 UTC, Andre Pany wrote: Does it make sense to open a DIP? It would make UDA quite nice to use if you can group several attributes into a struct. Or someone know whether there are already known issues why it isn't possible? The entire point of a DIP is to do this research for everyone and summarize it an easy-to-access and easy-to-find fashion ;-) FWIW there is an abandoned DIP for in-place struct initialization (https://github.com/dlang/DIPs/pull/22) - it might make sense to invest the effort to revive it from the dead...
Re: Concerns about using struct initializer in UDA?
On Thursday, 11 May 2017 at 10:49:58 UTC, Andre Pany wrote:
Hi,
I know there are concerns about struct initialization in method
calls but what is about struct initializer in UDA?
Scenario: I want to set several UDA values. At the moment I
have to create for each value a structure with exactly 1 field.
But it would be quite nice if I could use struct initialization
to group these values:
struct Field
{
string location;
string locationName;
}
struct Foo
{
@A = {locationName: "B"} int c; // <--
}
void main() {}
Of course the syntax is questionable, it is just a proposal.
What do you think?
Kind regards
André
I'm not sure if it isi what you're looking for but you can do
struct Field
{
string location;
string locationName;
}
struct Foo
{
@Field("","B") int c;
}
We use this for our compiler recognised attributes in LDC, see
llvmAttr for an example
(https://github.com/ldc-developers/druntime/blob/ldc/src/ldc/attributes.d#L108)
Re: Concerns about using struct initializer in UDA?
On Thursday, 11 May 2017 at 11:57:01 UTC, Stefan Koch wrote: On Thursday, 11 May 2017 at 11:36:17 UTC, Andre Pany wrote: On Thursday, 11 May 2017 at 10:51:09 UTC, Stefan Koch wrote: On Thursday, 11 May 2017 at 10:49:58 UTC, Andre Pany wrote: [...] We have that syntax already. I do not understand. Should the syntax I have written already work as I expect or do you mean my proposal is not possible as the syntax is ambiguous? Kind regards André I thought it should have worked already. My apologies the struct literal initialization syntax is unsupported because of the parser implementation. I don't know if you would introduce new ambiguities; I suspect that you wouldn't. Does it make sense to open a DIP? It would make UDA quite nice to use if you can group several attributes into a struct. Or someone know whether there are already known issues why it isn't possible? Kind regards André
Re: Concerns about using struct initializer in UDA?
On Thursday, 11 May 2017 at 11:36:17 UTC, Andre Pany wrote: On Thursday, 11 May 2017 at 10:51:09 UTC, Stefan Koch wrote: On Thursday, 11 May 2017 at 10:49:58 UTC, Andre Pany wrote: [...] We have that syntax already. I do not understand. Should the syntax I have written already work as I expect or do you mean my proposal is not possible as the syntax is ambiguous? Kind regards André I thought it should have worked already. My apologies the struct literal initialization syntax is unsupported because of the parser implementation. I don't know if you would introduce new ambiguities; I suspect that you wouldn't.
Re: Concerns about using struct initializer in UDA?
On Thursday, 11 May 2017 at 10:51:09 UTC, Stefan Koch wrote:
On Thursday, 11 May 2017 at 10:49:58 UTC, Andre Pany wrote:
Hi,
I know there are concerns about struct initialization in
method calls but what is about struct initializer in UDA?
Scenario: I want to set several UDA values. At the moment I
have to create for each value a structure with exactly 1
field. But it would be quite nice if I could use struct
initialization to group these values:
struct Field
{
string location;
string locationName;
}
struct Foo
{
@A = {locationName: "B"} int c; // <--
}
void main() {}
Of course the syntax is questionable, it is just a proposal.
What do you think?
Kind regards
André
We have that syntax already.
I do not understand. Should the syntax I have written already
work as I expect or do you mean my proposal is not possible as
the syntax is ambiguous?
Kind regards
André
Re: Concerns about using struct initializer in UDA?
On Thursday, 11 May 2017 at 10:49:58 UTC, Andre Pany wrote:
Hi,
I know there are concerns about struct initialization in method
calls but what is about struct initializer in UDA?
Scenario: I want to set several UDA values. At the moment I
have to create for each value a structure with exactly 1 field.
But it would be quite nice if I could use struct initialization
to group these values:
struct Field
{
string location;
string locationName;
}
struct Foo
{
@A = {locationName: "B"} int c; // <--
}
void main() {}
Of course the syntax is questionable, it is just a proposal.
What do you think?
Kind regards
André
We have that syntax already.
Concerns about using struct initializer in UDA?
Hi,
I know there are concerns about struct initialization in method
calls but what is about struct initializer in UDA?
Scenario: I want to set several UDA values. At the moment I have
to create for each value a structure with exactly 1 field. But it
would be quite nice if I could use struct initialization to group
these values:
struct Field
{
string location;
string locationName;
}
struct Foo
{
@A = {locationName: "B"} int c; // <--
}
void main() {}
Of course the syntax is questionable, it is just a proposal.
What do you think?
Kind regards
André
