I'm mostly with Ron on that — to me, merely declaring/documenting
:default ::= action => [name,values]
as the current best practice to start grammar development by looking at the
names/values returned by the recognizer, like that once was the case
with :default
::= action => ::array seems to be a better way to introduce it when
compared with new SLIF DSL syntax or use Marpa::R2 qw(if2).
As for backward compatibility concern related to
lexeme default = latm => 1
I'd just refwer to my (possibly mistaken) opinion in previous RFD.
On Mon, Feb 24, 2014 at 1:08 AM, Jeffrey Kegler <
[email protected]> wrote:
> I've taken input from the first RFD on this topic, and have added some new
> features to Marpa. What I propose to do now is to allow you to specify
> "if2" in Marpa::R2's import list. That is, you can do
>
> use Marpa::R2 qw(if2);
>
> If you choose to specify interface 2 this way, your defaults will change
> to the following:
>
> :default ::= action => [name,values]
> lexeme default = latm => 1
>
> Here "name" is a new array descriptor element, whose value for a rule is
> the rule's name, if it has one. For an unnamed rule it is the name of the
> LHS, and for lexemes and nulled symbols, it is the symbol name.
>
> The "latm" adverb is new, but it's just a synonym for "forgiving". The
> "forgiving" adverb is also retained, for backward compatibility. I've
> added "latm" because "forgiving" describe the behavior in terms of a now
> obsolete implementation. The behavior is Longest Acceptable Tokens
> Matching, so it's easiest to call it that.
>
> Rule names can be defined with a new "name" adverb, which can used as
> follows:
>
> start ::= number1 number2 name => top
> number1 ::= <forty two> name => 'number 1'
> number2 ::= <forty three> name => 'number 2'
>
> Please let me know your thoughts,
>
> -- jeffrey
>
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