gnubol: A question

[Michael McKernan <mck@tivoli.mv.com>]

for Randall Bart or whomever might have a defensible opinion.

I'm looking at how we might resolve the syntactic ambiguity of
abbreviated conditionals and condition names at parse time rather
than later in he compilation.  The problem was cited by Christopher
Clark and I have included the relevant part of his message at the end
of this one.

My question is really about abbreviated conditionals, apart from this
classic gotcha.  What effect do parenthesized expressions have on
abbreviation?  If I encounter the following

	 IF a = b OR ( c < d AND e < f ) OR g

and "g" is indeed a simple variable, should I interpret this to mean

	 IF a = b OR ( c < d AND e < f ) OR e < g

or perhaps

	 IF a = b OR ( c < d AND e < f ) OR a = g

or should it be diagnosed?  I've never been sure we've gotten this
one right in the past, evidenced by the fact that I can't remember
which way we did it.  I probably got an expert interpretation then,
but I need one again.

Thanks,

Mike  

    

Christopher's example:

  ...

01  X PIC 9 VALUE 1.
01  Y PIC 9 VALUE 2.
*    88 Z VALUE 2.
01  Z PIC 9 VALUE 2.

PROCEDURE DIVISION.
MAIN.
    IF X = Y OR Z
        DISPLAY "s"
    ELSE
        DISPLAY "f"
    END-IF.

===========>8===============

    And point out that the IF statement _parses_ differently depending on which
version of Z is included, since as a field, the actual test is:

    (X = Y) OR (X = Z)

    <value1> = <value2> OR <value3>
        => <simple-condition> OR <value3>
        => <abbreviated-combined-condition>

    but if the 88 version is included, the actual test is:

    (X = Y) OR Z              =>        (X = Y) OR (Y = 2)

    ...






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