Jonas Maebe wrote:
On 15 Apr 2013, at 16:48, Mark Morgan Lloyd wrote:
I was having a bit of fun earlier while waiting for a call. Am I correct in
believing that something like
type t1= array of integer;
var a1: t1;
x: integer;
a1 := [1,2,3,4,5];
can't be done at present, irrespective of any custom definition of the :=
operator?
Maybe if you overload the assignment operator for "t2=set of byte" to "t1"
assignments, but I'm not certain. It's definitely not something we explicitly support.
That's a good point, although obviously ordering would be lost. After
I'd tinkered with it for a while I concluded that it was probably
related to the discussion of tuples a few weeks ago.
Is there an accessible not-a-number constant, to allow me to do something like
var reduce: double= NAN;
x := reduce + a1;
with an appropriate definition of the + operator without risk that an error
would try to evaluate it as an ordinary arithmetic expression?
We don't have constant to identify a qNaN. I don't even know whether all
architectures support them. Currently, the only way to achieve the above is by
masking exceptions for invalid floating point operations:
math.SetExceptionMask(math.GetExceptionMask + [exInvalidOp]).
Thanks, noted. In practical terms the value isn't important, and I could
obviously use something like a null variant or for that matter a nil
pointer as a marker.
You cannot overload/override operators that have a built-in meaning in the
language (such as double+double).
Understood, but what I'm doing here is using "reduce +" as an
experimental alternative to APL's +/ or Vector Pascal's \+ to reduce the
dimension of the right operand by applying the operator:
c1:
7 9 11 13 5
+/ c1:
45
I've not investigated SSE or spreading over multiple cores yet, and
probably won't due to time issues. My only incentive was looking for
some alternative to Vector Pascal's higher-level functions, since
obviously something like \<operator> <array> couldn't be achieved
without major compiler surgery.
--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]
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