Hello,
I can extract from some data structures a set of grammar rules that looks
like:
topLevelRule1 ::= rule1 rule2 rule3
topLevelRule2 ::= rule2
rule1 ::= rule11 rule12
rule11 ~ token11
rule12~ token12
rule2 ~ token2
rule3 ~ token3
.... and so on (any kind of nested structures of this kind are to be
expected),
and I would like to create a Marpa grammar from this to
parse against some MathML stuff ( and replace subtrees according to it.)
Now the input is not completely described by the grammar, so I would want
to
use some kind of structure like:
Script ::= Notation (top level rule -> that is what I am going to replace)
|| Presentation (other MathML not described by my grammar)
|| Content (stuff that was already replaced on a previous run or by
any other means)
|| Error (anything)
The problem is that the top level rules have precedences that have to be
taken into
account.
-> I have tried using || to implement that, but found out that its action
is not deterministic and hence useless for my purpose.
-> I have also tried to use ranking_method in order to implement this,
but it just doesn't work out.
So, my question is as follows - if I have a (potentially large) set of
alternative rules with
certain precedences, how do I define a grammar like that ( also taking into
account the possibility of ambiguous parses) - so that I can use the
"event" adverb
to actually perform some substitutions.
To make it clearer - I would be happy enough even if I only got an answer
to how the following
should be implemented so that the alternative "|| Other action =>
do_printErr" is ONLY
executed if the first alternative failed.
:start ::= Script
Script ::= Number ',' Number action => do_printNr
|| Other action => do_printErr
Other ::= Error
Error ~ [\s\S]*
Number ~ digits
digits ~ [\d]+
Thank you in advance for help,
Toloaca Ion
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