Per suggestions, for example this one and Ron's, I am going to shelve
the idea of an "if" or "interface" option. For the time being,
resetting the defaults by specifying the options at the beginning of the
script as a kind of "incantation" should be adequate.
-- jeffrey
On 02/24/2014 12:25 AM, Ruslan Shvedov wrote:
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]
<mailto:[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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