This is an issue that comes up repeatedly, and with
very good reason. We should blame Aristotle, Aquinas,
Leibniz, Boole and various others, no doubt.
However, it is, I guess, far too late to allow what
Bill wants to be done.
Or, what amounts to the same thing, it is too
radical.
Suppose in version 9, <snafu> is treated as true if
<snafu> is non-zero and non-missing, while the previous
syntax (non-zero is sufficient) is allowed under
version control. I suspect that this woould in turn be
a source of confusion, _especially_ for
longstanding Stata users.
Pandora's brother opened the box long ago
and it cannot now be shut.
What I think is a bit more likely is
some other syntactical way of doing this.
What about some functions
pos()
nonzero()
pos() would return 1 if its argument was positive
and non-missing and 0 otherwise.
nonzero() would return 1 if its argument
was non-zero and non-missing and 0 otherwise.
if pos(snafu)
would then be
a way of writing
if snafu > 0 & snafu < .
Nick
[email protected]
Bill Rising
> >One can certainly be bit by forgetting that
> >
> > <expression evaluating to numeric missing>
> >
> >qualifies as true. This may not be what you want,
> >but the point is very well documented.
>
> It is well documented, and I suspect that there is a good
> internal coding
> reason for it, since C assumes that non-zero (i.e. any bit
> non-zero) is
> true, and missing values have non-zero bits. Still, it
> would make Stata
> code easier to read and less prone to error if people could
> code the
> incorrect
>
> regress foo bar if snafu
>
> instead of the correct
>
> regress foo bar if snafu & snafu < .
>
> for snafu being some sort of indicator which could be missing.
>
> I've used Stata long enough that the latter comes natural
> to me. Still,
> I'd hate to see how many analyses have been found invalid
> because of
> folks forgetting the extra 'less than missing' clause.
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