On Oct 16, 2008, at 7:04 PM, Waldemar Horwat wrote:
The parser is required to backtrack until it either finds an
expansion of the grammar that doesn't generate a syntax error or
until it discovers that they all do. You can choose to make
additional syntax errors as per chapter 16, but that does not
relieve you of the backtracking requirement.
You're right that a bottom up parser will have a reduce-reduce
conflict. For a top-down parser, it's not an issue.
Other examples: What does the following do?
for (a = let (b = c) b in d) ...
SyntaxError because no ; after first expression in for (;;) loop
head.
It can't be a SyntaxError. It's a perfectly valid for-in statement.
Is this a perfectly valid for-in statement?
for (a = b in c);
Not according to ES3's grammar. An assignment expression is not valid
on the left of the for-in's "in":
IterationStatement :
...
for ( LeftHandSideExpression in Expression ) Statement
for ( var VariableDeclarationNoIn in Expression ) Statement
LeftHandSideExpression does not produce an unparenthesized
AssignmentExpression, and if you parenthesize then PutValue will
throw on the non-Reference result of the assignment, the
ReferenceError at runtime which again can become SyntaxError at
compile time.
/be
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