Re: Parsing Questions

Stefan Ewing wrote:
> How can the postfix increment/decrement operators in C, C++, and Java
> be represented in a parse tree? For example, if we have the
> epxression
>
> a = b++ + c;


The parse tree for this would be


        +
      / \
.++ c
    |
    b


(.++ indicating the postfix ++; you'd have different encodings for
prefix and postfix ++.)


> b will be incremented after b + c has been calculated.


Nearly, but not quite.
The .++ operator should return the value of b, then increment b. (This
may sound nonsensical, but on an implementation level, functions can
prepare the return value, do a few other things, and then actually return.)


> Also, how should one represent the Java field access operator (.) in
> a parse tree? At first glance, it seems like a binary operator to
> me (given the object name and the field name, a memory address is
> returned), but one operator precedence chart I saw online shows . as
> a unary operator.


The chart is wrong (there's always the possibility of a typo after all),
or it is based on a grammar that doesn't follow the normal operator
precedence patterns (e.g. if the grammar defines an access path as a
sequence of "access elements", each element being a name prefixed with a
dot).


Regards,
Joachim
--
This is not an official statement from my employer.

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