Re: Reasons (not) to vote Motion 27: NO
On 2011-08-18 10:10:06 -0500, Ralph Baker Kearfott wrote:
> Vincent et al,
>
> I'm still a bit confused about specifying over "free expressions"
> versus "bound expressions," since my perception of the scope
> of the standard is specification of individual operations,
> rather than in the parsing of expressions in a programming
> language. However, I suppose we can define the individual
> operations (including possible decorations) according to
> their effect on expressions, and whether or not we are
> thinking of free expressions or bound expressions would
> affect how we do this.
The specification on free expressions can be derived from the
specification of individual operations, since a free expression
is just made of operations. So, the standard can just specify
the individual operations.
This is not true for bound expressions, unless the programmer
does something about the empty intervals. Indeed, consider a
free expression Expr(x1,x2,...,xn); its evaluation is specified
by the individual operations. But concerning bound expressions,
(x1,x2,...,xn) |-> Expr(x1,x2,...,xn)
and
(x1,x2,...,xn,y1,...,ym) |-> Expr(x1,x2,...,xn)
(computed by the same operations) are not equivalent: the result
can differ if at least one of the y components is empty.
IMHO, the decoration system, defined by the specification of the
individual operations, should be meaningful on free expressions.
Motion 26 does probably too much by differentiating ein, emp and
ill (is it really necessary to differentiate them?).
--
Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)