On Wed, 2011-02-16 at 17:12 +0100, Thomas Bellman wrote:
> On 2011-02-12 17:36, Brice Figureau wrote:
>
> It appears that I'm late to the party, but:
>
> > The following manifest was producing a parse error:
> > $int = { 'eth0' => 'bla' }
> > $foo = $int['eth0'] ? {
> > 'bla' => 'foo',
> > default => 'bleh'
> > }
> >
> > because selectors didn't support hash access.
>
> > diff --git a/lib/puppet/parser/grammar.ra b/lib/puppet/parser/grammar.ra
> > index 7a316d4..3a386d8 100644
> > --- a/lib/puppet/parser/grammar.ra
> > +++ b/lib/puppet/parser/grammar.ra
> > @@ -642,6 +642,7 @@ selectlhand: name
> > | funcrvalue
> > | boolean
> > | undef
> > + | hasharrayaccess
> > | DEFAULT {
> > result = ast AST::Default, :value => val[0][:value], :line =>
> > val[0][:line]
> > }
>
> Question: why does the grammar not allow a generic rvalue here instead
> of only allowing a few ways of specifying values? This question applies
> to lots of other places in the grammar as well, like resource names or
> function paramaters (you can't use a function call for a resource name,
> and you can't specify a literal array as a function parameter, but have
> to assign them to a dummy variable first).
The reason is that racc produces tons of reduce/shift conflicts if you
use rvalue instead of a selectlhand. I'm not exactly sure why it does
this (as I think yacc wouldn't do that for the same grammar).
It might be possible that it doesn't like some kind of recursion.
> And even so, shouldn't the above patch add "hasharrayaccesses" (plural)?
I think you are right.
Daniel (or who is the current "merge-captain" right now): should I send
a new patch?
> I'm not a parser expert, and this is the first time I've even looked at
> grammar.ra, but as a user of Puppet I find those restrictions annoying...
One thing I'm sure when I started hacking on the Puppet grammar is that
I didn't want to transform the DSL in a full-blown generic language.
So for instance it's not possible to use an expression in the context of
any rvalues.
--
Brice Figureau
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