I currently implementing a JavaScript/ ECMAScript 5.1 parser with JavaCC and have problems with the ArrayLiteral production.
ArrayLiteral :
[ Elision_opt ]
[ ElementList ]
[ ElementList , Elision_opt ]
ElementList :
Elision_opt AssignmentExpression
ElementList , Elision_opt AssignmentExpression
Elision :
,
Elision ,
I have three questions, I'll ask them one by one.
I have tried to simplify/to rewrite the ArrayLiteral
production depicted above and finally arrived to the following production (pseudo-grammar):
ArrayLiteral:
"[" ("," | AssignmentExpression ",") * AssignmentExpression ? "]"
My first question: is this rewriting correct?
Two other quetsions:
Yes, that correctly captures the grammar presented.
However, a better rewrite would be:
"[" AssignmentExpression ? ( "," AssignmentExpression ? ) * "]"
because the rewriting in the OP is not LL(1) -- you cannot distinguish the possibilities without reading the entire AssignmentExpression
-- whereas with this one you can figure out which alternative to use simply by looking at the first token.
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