Re: Can an alias be used to define a new anchor?

On Tue, Sep 9, 2014 at 2:32 PM, Peter Murphy <[email protected]> wrote:

> On Tue, Sep 9, 2014 at 9:27 PM, Bartek Grychtol <[email protected]>
> wrote:
> > Hello List,
> >
> > I'm new to YAML, which we're using in a project via yaml-cpp. I stumpled
> > into an issue which I don't know if it's a bug in yaml-cpp or a feature
> of
> > the spec. I consulted the spec but left no wiser.
> >
> > I wanted to write a node like this:
> > ---
> > Images:
> >  one:
> >   size_x: &ONE_SIZE 100
> >  two:
> >   size_x: &TWO_SIZE *ONE_SIZE
> >
> > That is, I was hoping to use an alias to define a new anchor. The
> motivation
> > is that *TWO_SIZE is used lower down independently of *ONE_SIZE, yet they
> > are sometimes, but not always, one and the same thing.
> >
> > yaml-cpp refuses to parse this. Is it legal YAML?
> >
> > Thanks in advance!
> >
> > Bartek
> >
>
> Bartek,
>
> I'm afraid it is not legal YAML. Once you assign an anchor name to a
> node, you have to reuse that anchor name for all aliases.
>
> The production for aliases is under section 7.1.
>
> http://www.yaml.org/spec/1.2/spec.html#id2786196
>
> [104]   c-ns-alias-node         ::=     “*” ns-anchor-name
>
> [102]   ns-anchor-char  ::=     ns-char - c-flow-indicator
> [103]   ns-anchor-name  ::=     ns-anchor-char+
>
> In the current spec (1.2), there is no way of assigning multiple
> anchor/alias names to the same node.
>
> However, there may be future versions of the spec which don't have
> this limitation.
>
> Best regards,
> Peter
>
>
Hi Peter,

Thanks a lot for the quick answer. I guess I'll have to work around it then.
I wonder what's the reason behind this design decision, though..?

Best,
Bartek

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