On Thu, May 2, 2019 at 3:51 PM Greg Wilburn
<gwilburn@xxxxxxxxxxxxxxxxxxxxxxx> wrote:
My problem was twofold
1. I was using SQL to retrieve the string - you can't do that directly into RA0094
2. The array needs ASCEND or DESCEND to use %lookuple
Since you said you're converting from the old LOOKUP opcode, you
should be aware of another difference between it and the BIFs: The
opcode searches sequentially; the BIFs use binary search. Which means
you have to make sure of two things when using the BIFs: First, the
data needs to ACTUALLY be sorted (not just *declared* sorted). Second,
which is actually just a stricter expression of the first, if your
array isn't "full" then you have to be sure to specify the
"startindex" and "numelems" parameters when you do the lookup, or you
have to fill any trailing array elements with *HIVAL beforehand. Or
just sort the whole array with SORTA.
This has bitten me more than once. One common efficient-seeming
pattern for building an array is by reading in sorted values. Figuring
that the data going in is already sorted, there's no need to use SORTA
afterwards; that would just be redundant. But it wouldn't, if you
don't have enough values to fill the array. You can get away with this
bit of sloppiness with the opcode, because it searches sequentially.
But binary search will be screwed up by this. (If you take the time to
work out why this is, with pencil and paper if necessary, you will
etch it into your brain and be much less likely to be caught out by
this.)
John Y.
midrange.com
