NICE-ESG-Libs Digest        Wed, 28 Feb 96       Volume 2 : Issue  23 

Today's Topics:
                         Operator precedence


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Date: Tue, 27 Feb 1996 18:22:36 -0800 (PST)
From: ericb@eiffel.com (Eric Bezault)
Subject: Operator precedence
To: NICE-ESG-Libs@atlanta.twr.com (NICE ESG LIBS)

Dear Library Committee members,

Today in an article in comp.lang.eiffel, Christian P. Schinagl pointed out
a bug in some of ISE's postconditions with respect to operator precedence
between `=' and `and'. I checked in class ARRAY proposal and found the
following similar problems:

o proposal RB-3 (updated with my remarks from V2 #22):

        definition: -- Result = (lower = other.lower) and (upper = other.upper)
            and then for_all i, lower..upper (item (i) = other.item (i))

  should be replaced by

        definition: -- Result = ((lower = other.lower) and (upper = other.upper)
            and then for_all i, lower..upper (item (i) = other.item (i)))

o postcondition of feature `valid_index':

        -- Defined here as   Result = (lower <= i) and (i <= upper)
        -- May be redefined in descendants.

  should be replaced by

        -- Defined here as   Result = ((lower <= i) and (i <= upper))
        -- May be redefined in descendants.

I will have a look at all ELKS classes the next time I update the FrameMaker
document on ISE's ftp site.

Best regards,

-- 
Eric Bezault 
Interactive Software Engineering Inc.
270 Storke Road, Suite #7                      / Tel +1 (805) 685-1006 \
Goleta, California 93117, USA                  \ Fax +1 (805) 685-6869 /