On 1/2/12 11:18 PM, David Mertens wrote:
Because PDL doesn't like boolean evaluations **except for single-element
piddles**, this expression will croak if $a is anything more than a
one-dimensional vector. Have you tried running that conditional when $a
is more complex? For example, if $a is a matrix, this will croak.
Something I didn't realize, but just learned messing with this, is that
a single BAD value is considered boolean false. That's more clever than
I had expected. :-)
It's kind-of discussed in
http://pdl.perl.org/PDLdocs/BadValues.html#bad_values_and_boolean_operators
(or, perhaps, this is out of date and needs re-writing), but it may well
make sense for someone (not me, as I don't have the energy) to move the
operational/useful parts of this document to PDL::Bad, leaving the
BadValues document more for the
implementation/you-don't-need-to-read-this-to-just-use-it documentation.
I can't remember if the docs for PDL::Bad is empty if support is not
included, and - of so - whether it is that serious an issue (since if
you don't have the support compiled in then you don't really need to
know about how it works).
In PDL 2.4.10, you should be able to return pdl('bad'). That's a recent
implementation of mine. :-) Alternatively, perhaps PDL should add BAD to
PDL::Constants (as well as INF, for that matter).
As the bad-value can be changed for the integer types (and even
floating-point types, depending on how the code is built), I'm not sure
that you can really treat it as a constant, but this comment comes after
spending all of 5 seconds thinking about the matter, so I may well be
missing something completely obvious here ;-)
Doug
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