Just off the top of my head, &. and |. seem to make sense since . is
called "full stop" in some places :-) .
On 9/24/2014 10:17 AM, Rick McGuire wrote:
I've started coding this up, and the "," syntax for list creation
looks very doable. The meaning of the "," depends on the context, as
already noted, but the contexts are absolutely unambiguous so it is
always possible to assign the correct meaning.
However, I want to circle back around to the discussion of the
short-circuited AND. We can't eliminate the usage on IF/WHEN, etc.,
but on the other hand, there are certainly contexts where an and
operator that uses short-circuit logic might be useful. One could
argue that an OR version could also be useful. I don't believe this
is possible for XOR, since the result always depends on both values.
Are there any operator combinations that would make sense? Doubling
up obviously doesn't work because && and || are already operators.
Rick
On Sat, Sep 20, 2014 at 10:41 AM, Mike Cowlishaw <[email protected]
<mailto:[email protected]>> wrote:
On further reflection, the conditional expression cannot
be merged with a simple redefinition. The conditional
expressions have the "shortcut" feature where not all of
the expressions need to be evaluated. The conditionals
will still need to be a special case because of that.
Also on further reflection .. perhaps the
conditional case could drop the shortcut
feature. In other words: all the expressions
are evaluated, and if any of them are true
then the THEN/WHEN path is taken.
No, we can't do that. The whole point of that feature
was to allow for the shortcut to happen! This allows
for tests like
if a~isa(.String), a~length > 0 then
to work. This instruction would give an error if all
of the expressions are evaluated because the second
test is only value if the first test is true. Making
that change would break every single program I've
written that uses that construct since I only use that
sort of conditional because of the shortcut behaviour.
Understood ... shortcut mechanism is good. What I'm
suggesting is that my choice of using commas to
indicate that behavior could perhaps be improved upon,
especially given the recent discussion.
Or, more generally ... some way to apply shortcuts in
all expressions, not just in the IF/WHEN special case.
I don't think ooRexx needs to follow NetRexx in this
.. hindsight has value.
ooRexx has already followed NetRexx in this and even gone a
little beyond in adding this also to while and until loop
conditions. I don't see how shortcutting would have any
meaning in the other places where we'd wish to generate lists
of items. All of the expressions really need to be evaluated
in those situations to generate the array. The list usage in
conditionals really is quite a different construct. In
addition to the shortcut evaluation, they also do not allow
omitted expressions, which work just fine in the other
contexts (e.g., argument lists).
I don't really see much value into trying to force-fit these
together. It's not really necessary to have everything work out.
I guess I wasn't explicit enough. I was thinking that using
commas for the 'short cut' case was short sighted, and maybe a
different syntax for that would be better. So the comma
notation would always be 'evaluate them all' and something
different would be 'this is a sequence of logical tests
that can be short-circuited'. (Consider & vs. && in C.)
Commas might indeed be the best, here, but worth exploring
alternatives, briefly at least?
Mike
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