Steve Holden <[EMAIL PROTECTED]> wrote:
> In other words,
>
> assignment_stmt ::= (target_list "=") expression_list |
> (target_list "=") assignment_stmt
>
> and
>
> assignment_stmt ::= (target_list "=") assignment_stmt |
> (target_list "=") expression_list
>
> are entirely equivalent
I'm not quite sure what you are getting at. An assigment_stmt and an
expression_list are not ambiguous so those two productions are identical
(not just equivalent). Perhaps you are thinking of productions like:
m_expr ::= u_expr | m_expr "*" u_expr
which will match the same input, but could produce a different parser
output than:
m_expr ::= u_expr | u_expr "*" m_expr
> I'm sure you understand that syntax only specifies what's legal, not how
> it should be interpreted.
I agree that the syntax does not mandate how it should be interpreted,
but it does lead to expectations.
If the expression_stmt is hidden from the outer assignment_stmt by an inner
one then it is reasonable to expect that the inner production will be
completely evaluated before the outer assignment happens. i.e. right to
left.
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