J3/03-198

Date:     August 1, 2003
To:       J3
From:     Dick Hendrickson
Subject:  mask-expr evaluated only once

Robert Corbett asked whether or not a mask-expr is required
to be evaluated in a WHERE such as

      WHERE ( (/ .TRUE., .TRUE. /) )
        A = A + 1
      ELSE WHERE (MASKF())
        A = MAX
      END WHERE

where an optimizing compiler might notice that the ELSEWHERE
branch will never be executed.

Page 149, line 13 of J3/03-007 say of the mask expression in
ELSEWHERE statements

"The mask-expression is evaluated only once."

I think that's a mistake in the wording.  It appears to be
copied from 149:7 where it is correct.  The intent is to not
allow mask-exprs to be evaluated more than once to form the
control mask and the pending control mask.  I think the
wording just missed the case where evaluation isn't needed at
all.


PROPOSAL:

149:13  Change "only once" to "at most once"

149:22  Change "only once" to "at most once"