[Remind-Fans] Forward scanning, how?

[David F. Skoll]

David wrote:

> What I seek is similar to "backward scanning" but I want to go
> *forward* in time.

Because of the Remind algorithm (described in the slides at
http://www.roaringpenguin.com/files/download/remind-oclug.pdf) this is
tricky.  You have to warp your mind and think backwards.  Rather than
saying:

> ... generate a reminder 30 days following the 17th day of each month.

Think of it as:

> ... scan forward for dates that satisfy the condition: "30 days ago,
> it was the 17th".

which leads to:

REM SATISFY [day(trigdate()-30) == 17] MSG Woot!

In general, Remind *always* works like this:

"Scan forward (usually from today) until the date satisfies *some condition*..."

The built-in backward-scanning operations just modify the "satisfies
some condition" part, not the "scan forward" part.  That is:

     REM 1 --1 MSG Last day of the month

does not mean:  "Go the the first day of a month, then go back a day."

It means: "Scan from today until you hit a date which would result in
the first of a month if you add one day."

Regards,

David.