show alert if not true

I have a statment below which I can't get to work. Basically revision
letters need to be A then B then C then D etc If the revision letters are
not in this order then I want to show awarning.
In other words:
If RevLettOld equals "A" and RevLettNew equals "B"
or RevLettOld equals "B" and RevLettNew equals "C"
or RevLettOld equals "C" and RevLettNew equals "D"
and so on right through the alphabet
then proceed
however if for example RevLettOld equals "A" and RevLettNew equals C or D or
E or F G etc
and so then show alert box with warning message.
I guess I could make the statement :
if RevLettOld equals "A" and RevLettNew equals "C" or "D" or "E" or "F"
or "G" or "H" etc
and
if RevLettOld equals "B" and RevLettNew equals "D" or "E" or "F" or "G" or
"H" etc
etc etc etc
then show alert box
But I think this is a little cumbersome. Surely there must be a better way
to write the above expression

here is my attempt, but I can't seem to get it right

(if
(not
(and
(= RevLettOld "A")
(= RevLettNew "B")
);and

(or
(and
(= RevLettOld "B")
(= RevLettNew "C")
);and
);or

(or
(and
(= RevLettOld "C")
(= RevLettNew "D")
);and
);or

);not

(progn
(alert (strcat"\nRe-check rev letter and try again.... "

);strcat
);alert
);progn

);if

thanks Russ

 

Hi Russ,

Doubtful I understand what you are trying to do. But I wonder if you could just
check to see if a list is in ascending order?

(setq lst '("A" "B" "C" "D"))
(if (not (equal lst (vl-sort lst '<)))
(princ "alert")
(princ "OK")
)

Joe Burke

 

Hi Joe
I have an attributed title block and one of the tags is the
revision letter. I'm trying to compare the old revision letter with the new
revision letter. If "A" is not followed by a "B" or "B" is NOT followed by a
"C" etc then I want to show a warning so that the user must type in a "B" if
the existing rev is a "A" and so on.
I hope that makes sense
cheers
Russ

 

(if (= 1 (- (ASCII RevLettNew) (ASCII RevLettOld)))
thendothis
(alert "wrong")
)

Tom Berger

 

Russ,

Let's try this to see if I understand. Assume you know the old/existing revision
letter is "A". You prompt the user for a new revision letter to replace "A",
which must be "B", otherwise alert. The function needs to deal with whatever the
old revision letter was. If it was "R", the user must enter "S". You can't use
initget and getkword because those don't work with getstring.

Am I on the right track? If not, it's not your fault. I seem to have my
thick-head on this evening.

If the above is correct, maybe the ascii function as follows.

(setq existing (ascii "A")) ;example - returns integer
(setq new (< prompt for new revision letter >))
(if (not (= (1+ existing) (ascii new)))
(princ "alert")
)

Totally untested, Russ.

Joe Burke

 

Strings comply with greater than (> ...) & less than (< .... )
AutoLISP functions.

(< "A" "B")
T

-David

 

Yea, but (< "A" "C") also evaluates to T

Tom Berger

 

If you plan on incrementing revisions, don't forget that not all sheets are
affect by a revision, so you may even have to skip a revision.

In the case of a Plan Checker he may or may not find an issue on one or more
sheets. There are also client revisions, design revisions, and inhouse
revisions to consider. so you may have a sheet with a revision of 1, 3, 4,
5, 7 etc.

Just my 2 cents.

 

You can force the input with initget and getkword.

(setq a "A")
(initget (chr (1+ (ascii a))))
(setq b (getkword (strcat "Old Rev.: " a "--Input new Rev.:")))

--
Ken Alexander
Acad2000
Windows2000 Prof.

"We can't solve problems by using the same kind
of thinking we used when we created them."
--Albert Einstein

 

You need just one (or ...) clause:

(if
(not
(or ...
(and ... ;;A/B
);;and
(and ... ;;B/C
);;and
(and ... ;;C/D
);;and
);;or
);;not
(alert "Your Message")
(progn
(do stuff)
(do more stuff)
);;progn
);;if

However, there are more efficient ways of doing what you want; see some of
the other replies.
___

 

Many thanks!!! everyone.
I have it solved now
cheers Russ

 

Russ,

And the solution was... ?

Joe Burke