Re: Problem using tlookup bif

[Luis Rodriguez <luisro58@xxxxxxxxx>]

Dennis,

This problem has piqued my curiosity, as LOOKUP is a opcode that I have not
used in a (very) long time. I found this in a Bob Cozzi article (
http://systeminetwork.com/article/built-functions-you-might-not-be-using-fully
)
:

"One thing that needs to be pointed out is that the %LOOKUP built-in
function performs a different routine to search the array than does the
legacy LOOKUP opcode. So there is a chance you could get a different result
if you blindly convert LOOKUP opcodes to %LOOKUP built-in functions.

LOOKUP generated a subroutine based on the Resulting Indicators and
performed a sort of linear scan to locate matching elements, whereas %LOOKUP
uses a binary search routine to find the elements. This means that if the
data is not sequenced, %LOOKUP could fail to locate the elements even if
they exist."

I wonder if David found a solution to his problem?

Regards,


Luis Rodriguez
IBM Certified Systems Expert — eServer i5 iSeries
--



On Thu, Dec 16, 2010 at 1:59 PM, Dennis Lovelady <iseries@xxxxxxxxxxxx>wrote:

> Yes.  So that would be relevant if David were using %TLOOKUPxx.  But he's
> not.  He's using the %TLOOKUP, which does not use binary search.
>
> Dennis Lovelady
> http://www.linkedin.com/in/dennislovelady
> --
> "A fanatic is one who can't change his mind and won't change the subject."
>        -- Winston Churchill
>
>
> > It looks to me like %TLOOKUPxx uses a binary search, as %lookupxx does.
> >
> > "Since a binary search is used by the %LOOKUPxx built-in functions for
> > a
> > sequenced array, and the correct function of a binary search depends on
> > the data being in order, the search may only look at a few elements of
> > the array. When the array is out of order, the result of a binary
> > search
> > is unpredictable. "
> >
> >
> > On 12/16/2010 10:23 AM, Dennis Lovelady wrote:
> > > The manual refers to both kinds of lookups.  The kind that David is
> > using is
> > > not of the %TLOOKUPxx set, the nearest I can determine.  The %TLOOKUP
> > BIF
> > > works by comparing each value starting with 1 and ending when a match
> > is
> > > found or the end of the table is reached.  Sequence is immaterial.
> > Or at
> > > least that's the way it was the first 35 years or so of the language.
> > >
> > > Dennis Lovelady
> > > http://www.linkedin.com/in/dennislovelady
> > > --
> > > "A diplomat is a person who can tell you to go to hell in such a way
> > that
> > > you actually look forward to the trip."
> > >          -- Caskie Stinnett
> > --
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