Re: [Xen-devel] [PATCH v2-resend 08/30] libxl: ocaml: support for KeyedUnion in the bindings generator.

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Campbell writes ("Re: [Xen-devel] [PATCH v2-resend 08/30] libxl: ocaml: 
support for KeyedUnion in the bindings generator."):
> On Tue, 2013-08-27 at 16:09 +0100, Ian Jackson wrote:
> > I think you have some confusion betwwen bar,baz and foo,bar ?  At
> > least, I hope so, as otherwise I haven't understood at all.
> 
> I don't think so, foo is an enumeration with possible values of "bar"
> and "baz".
> 
> The keyed union has a discriminator (called blargle in this example)
> which is of type "enum foo". There is then an anonymous union with two
> members, "bar" and "baz" corresponding to the possible values of
> blargle.

That's what I thought.  So this part is wrong then ?

]     We generate C:
]
]     enum { FOO, BAR } foo;
]     struct s {

> > Is this indirection (through S.t) really needed ?  It seems a bit
> > ugly.  But I'm no expert on ocaml syntax or style.
> 
> It's the common idiom in ocaml, for a reason I cannot remember. 

Fair enough.

> > > These type names are OK because they are already within the namespace
> > > associated with the struct "s".
> > > 
> > > If the struct associated with bar is empty then we don't bother with
> > > blargle_bar of "of blargle_bar".
> > 
> > I'm not sure I follow this observation.
> 
> In the type blargle__union we don't bother with the "of blargle_bar"
> case of the corresponding struct is empty.

So we generate
    type blargle__union = Bar of blargle_bar | Baz;
?  If this is legal ocaml syntax, then fine, I guess.  (I can't
remember what "of" does here.)

Ian.

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