Here's a loop I use for getting a next ID on a heavily used system...
LOOP UNTIL RECORDLOCKED(F.GRTRANS,NEXT.AVAIL) > 1 DO
LOOP WHILE READV z FROM F.GRTRANS,NEXT.AVAIL,0 DO NEXT.AVAIL += 1
REPEAT
RECORDLOCKU F.GRTRANS,NEXT.AVAIL LOCKED NEXT.AVAIL += 1
REPEAT
> -----Original Message-----
> On Behalf Of Gyle Iverson
> Subject: RE: [U2] [UV] WHILE READNEXT id DO
>
>
> Ray Wurlod opined:
> >Personally, I love this syntax. When training others, I
> >usually explain it in this form; READNEXT has to generate a
> >true/untrue value of some kind to determine whether to go down
> >its THEN or ELSE path. We take advantage of that "Boolean
> >context" to trigger the behaviour of WHERE or UNTIL in a
> >looping context.
> >
> >READNEXT is not the only statement that exhibits this
> >behaviour. Almost any statement that has THEN/ELSE can use
> >it. But READNEXT, READSEQ/READBLK are the most "sensible".
> [snip]
> >It would be nice were there a section in the BASIC manual
> >about the Boolean context of certain statements, but that's
> >only a minor complaint. Of course, each statement syntax that
> >appears to make at least one of THEN or ELSE mandatory would
> >need a note referring to this section.
>
> Hello, Ray.
>
> We can agree that the syntax has a certain appeal, yet finding a practical
> use for such has always escaped me in real applications for anything but
> READNEXT. Why? The syntax precludes handling of ON ERROR or
> LOCKED clauses.
>
> Never mind that the READNEXT, READSEQ and READBLK statements
> should [but do
> not] have an ON ERROR clauses. After all, files may be damaged or networks
> may be interrupted. I assume your "sensible" reference would not be so if
> these statements should later support such a clause.
>
> Writing robust, recoverable, error-tolerant code precludes taking the
> approach that a file I/O statement may have only a THEN or ELSE condition.
> Perhaps if there were a structured exception mechanism within BASIC one
> could safely use such syntax, but I discourage its use for anything but
> simple one-time utility programs.
>
> Best regards,
> Gyle
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