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digitalmars.D.learn - How to list all the manifest constants in a class or struct

reply Heromyth <bitworld qq.com> writes:
Here is a struct named S:

struct S
{
	enum X = 10;
	enum Y
	{
	  i = 10
	}
	enum Z = "str";
	struct S {}
	class C {}

	static int sx = 0;
	__gshared int gx = 0;

         shared void g();	
}

I want list all then the manifest constants in it.

I searched the std.traits and this forums, but get nothing.
Maybe, my real question is how to get the storage class for a 
member in a class or struct.

Thanks.
Jun 16 2018
next sibling parent reply Jonathan M Davis <newsgroup.d jmdavisprog.com> writes:
On Sunday, June 17, 2018 02:44:38 Heromyth via Digitalmars-d-learn wrote:

 Here is a struct named S:

 struct S
 {
   enum X = 10;
   enum Y
   {
     i = 10
   }
   enum Z = "str";
   struct S {}
   class C {}

   static int sx = 0;
   __gshared int gx = 0;

          shared void g();
 }

 I want list all then the manifest constants in it.

 I searched the std.traits and this forums, but get nothing.
 Maybe, my real question is how to get the storage class for a
 member in a class or struct.


As the storage class isn't part of the type, type introspection tends to
ignore it. You'll basically have to get the full list of members of the type
and then filter out stuff that isn't a manifest constant, which is not
exactly pleasant and can get a bit tricky but should be possible. You'll
probably have to do something like filter out all of the members where you
can take their address and filter out all of the ones that are types, and
and at that point, you'd be close, but I'd have to experiment to figure out
whether that was enough or not or whether something crept through.

Andrei has been working on coming up with a better wrapper around the
current introspection stuff so that you'll actually get data types which
contain the information about a symbol rather than having to figure out
which combination of __traits and traits from std.traits are required to get
what you want. So, I expect that stuff like this will get a lot easier once
that's ready, but in the interim, if you're trying to do something less
common, it can involve having to do a lot clever filtering to get exactly
the stuff you want and only the stuff you want - and I don't think that
getting the list of manifest constants in a type is a very typical thing for
folks to do, so std.traits certainly doesn't have anything like
isManifestConstant.

- Jonathan M Davis
Jun 16 2018
parent Heromyth <bitworld qq.com> writes:
On Sunday, 17 June 2018 at 04:32:29 UTC, Jonathan M Davis wrote:

 On Sunday, June 17, 2018 02:44:38 Heromyth via 
 Digitalmars-d-learn wrote:

 Here is a struct named S:

 struct S
 {
   enum X = 10;
   enum Y
   {
     i = 10
   }
   enum Z = "str";
   struct S {}
   class C {}

   static int sx = 0;
   __gshared int gx = 0;

          shared void g();
 }

 I want list all then the manifest constants in it.

 I searched the std.traits and this forums, but get nothing. 
 Maybe, my real question is how to get the storage class for a 
 member in a class or struct.


 As the storage class isn't part of the type, type introspection 
 tends to ignore it. You'll basically have to get the full list 
 of members of the type and then filter out stuff that isn't a 
 manifest constant, which is not exactly pleasant and can get a 
 bit tricky but should be possible. You'll probably have to do 
 something like filter out all of the members where you can take 
 their address and filter out all of the ones that are types, 
 and and at that point, you'd be close, but I'd have to 
 experiment to figure out whether that was enough or not or 
 whether something crept through.

 Andrei has been working on coming up with a better wrapper 
 around the current introspection stuff so that you'll actually 
 get data types which contain the information about a symbol 
 rather than having to figure out which combination of __traits 
 and traits from std.traits are required to get what you want. 
 So, I expect that stuff like this will get a lot easier once 
 that's ready, but in the interim, if you're trying to do 
 something less common, it can involve having to do a lot clever 
 filtering to get exactly the stuff you want and only the stuff 
 you want - and I don't think that getting the list of manifest 
 constants in a type is a very typical thing for folks to do, so 
 std.traits certainly doesn't have anything like 
 isManifestConstant.

 - Jonathan M Davis


Thanks for your answers. It's so glad to see some works have been 
taken for this.

The isManifestConstant is really necessary. For example, I want 
to port an Enum type from Java to D. It seems better to use a 
Struct instead of an Enum.

See here:
https://github.com/eclipse/jetty.project/blob/jetty-9.4.x/jetty-http/src/main/java/org/eclipse/jetty/http/HttpStatus.java
https://github.com/eclipse/jetty.project/blob/jetty-9.4.x/jetty-http/src/main/java/org/eclipse/jetty/http/HttpHeaderValue.java

Of course, I can define a enum for members with the basic types 
in D.
Sometimes, I like to define them in a class or struct as manifest 
constants or immutable ones. So, I need isManifestConstant.
Jun 17 2018
prev sibling parent reply aliak <something something.com> writes:
On Sunday, 17 June 2018 at 02:44:38 UTC, Heromyth wrote:

 Here is a struct named S:

 struct S
 {
 	enum X = 10;
 	enum Y
 	{
 	  i = 10
 	}
 	enum Z = "str";
 	struct S {}
 	class C {}

 	static int sx = 0;
 	__gshared int gx = 0;

         shared void g();	
 }

 I want list all then the manifest constants in it.

 I searched the std.traits and this forums, but get nothing.
 Maybe, my real question is how to get the storage class for a 
 member in a class or struct.

 Thanks.


I think this bolts.isManifestAssignable [1] will get you 
partially there. The place where it'll fail though is a static 
immutable (since they are assignable to manifest constants) but 
you can filter those by seeing if you can take the address, 
something like:

foreach (m; __traits(allMembers, T)) {
   if (isManifestAssignable!(T, m) && !is(typeof(mixin("&T."~m))) {
     // it's a manifest constant ... (?)
   }
}

There of course might be edge cases I can't think of/don't know 
about though.

Cheers,
- Ali

http://bolts.dpldocs.info/bolts.traits.isManifestAssignable.html
Jun 17 2018
parent Heromyth <bitworld qq.com> writes:
On Sunday, 17 June 2018 at 20:03:09 UTC, aliak wrote:

 On Sunday, 17 June 2018 at 02:44:38 UTC, Heromyth wrote:

 [...]


 I think this bolts.isManifestAssignable [1] will get you 
 partially there. The place where it'll fail though is a static 
 immutable (since they are assignable to manifest constants) but 
 you can filter those by seeing if you can take the address, 
 something like:

 foreach (m; __traits(allMembers, T)) {
   if (isManifestAssignable!(T, m) && 
 !is(typeof(mixin("&T."~m))) {
     // it's a manifest constant ... (?)
   }
 }

 There of course might be edge cases I can't think of/don't know 
 about though.

 Cheers,
 - Ali

 http://bolts.dpldocs.info/bolts.traits.isManifestAssignable.html


Thant's it. Thanks for your great lib: 
https://github.com/aliak00/bolts
Jun 17 2018