Resusing variables without having to set their value again
One way is to ask for such a value only if it does not already have one:
(if (not sc1) (setq sc1 (getreal "\n* Enter Plot Scale : ")))
which you will see some do this way:
(or sc1 (setq sc1 (getreal "\n* Enter Plot Scale : ")))
Kent Cooper, AIA 
@Anonymous wrote:
...
This is probably where the Conditional Statement comes into play .... it would roughly be like
(cond ((= sc1 nil)(= sc2 nil)(= th nil) ; (setting the values for these) ........
A couple of things about that:
[The (= sc1 nil) thing would work, but it's not necessary to check whether something is "equal to nil" -- you can just check whether it exists at all, with (not sc1) or (null sc1).]
The construction there would need to do one test per condition, and follow it with what to do if that one test does not return nil, rather than three in a row like that. If the idea is to test for the existence of values in all three before going on to set them if they don't exist, it would need to be more like:
(cond (and (not sc1) (not sc2) (not th))
....
or
(cond (not (or sc1 sc2 th))
....
But in such a case an (if) function would do just as well. And if by chance one or two, but not all, of those did have values, it would not ask for a value for the one(s) that didn't.
If you built it like this:
(cond
((not sc1) .... {ask for a value for that} ....)
((not sc2) .... {ask for a value for that} ....)
((not th) .... {ask for a value for that} ....)
); cond
then if sc1 had a value, it would never get to checking whether sc2 and/or th had values.
If there would always and unfailingly be values in all three variables if there was a value in any one of them, you could do something like this:
(if (not sc1) ; check for any one of them
(setq ; then -- get all three
sc1 .... {ask for a value for that} ....
sc2 .... {ask for a value for that} ....
th .... {ask for a value for that} ....
); setq
); if
Kent Cooper, AIA
@Anonymous wrote:
So if I used;
(defun c:WSH( / sset );Write Spot Height (or ( sc1 sc2 th) (setq sc1 (getreal "\n* Enter Plot Scale : ")) (setq sc2 (* (/ sc1 200) 1)) (setq th (* (/ sc1 1000.0) 2) ) ....Then if I redo the WSH function I will not have to assign a value to those variables each time I want to use it?
[I didn't notice before that the sc2 and th values are results of the sc1 value, so obviously it wouldn't be necessary to ask for values for the later ones after getting one for sc1, as I suggested.]
RE-EDIT: As written, sc1 would be taken as a function name. I think what you intend there is:
(or (or sc1 sc2 th)
or possibly
(or (and sc1 sc2 th)
But if that's how it's built, then go on to what I originally posted:
Suppose somehow there's a value in th but not in the others, however that might occur. The first construction above would not ask for an sc1 value, and therefore it would try to proceed without all the necessary values. Since you can't localize those variables if you want them reusable, but since the others are resultants from sc1, I would do it more like the end of my previous Reply, but of course with the sc2 and th values calculated from sc1 rather than asking for them.
Kent Cooper, AIA
@Anonymous wrote:
Okay so using the code you supplied. It would end up looking like so;
(if (not sc1) (setq sc1 (getreal "\n* Enter Plot Scale : ")) (setq sc2 (* (/ sc1 200) 1)) (setq th (* (/ sc1 1000.0) 2)And after doing this the first time, if I use the "WSH" command again, it will find out if "sc1" has a value and if so it will skip the "setq" stage?
[See my Edit to Post 7, just so you don't miss it.]
Yes except for missing a right parenthesis at the end of the th setting]. If there's a value in sc1, the (not sc1) will return nil, so it won't do what's called for as a 'thenexpr' argument. And you can shortcut that a little -- a single (setq) function can set more than one variable:
(if (not sc1)
(setq
sc1 (getreal "\n* Enter Plot Scale : ")
sc2 (* (/ sc1 200) 1)
th (* (/ sc1 1000.0) 2)
); setq
); if
If there's any possibility that sc1 might have a value but the others might not, consider having that set only sc1 within that (if) function, and then outside that, calculate sc2 and th. That way, it won't ask for sc1, but it will still put values into sc2 and th.
Kent Cooper, AIA
@john.uhden wrote:
.... you could make it easy by making the previous value the default so if the user wants to use the previous value, then all he has to do is hit Enter...
Let's say that the most popular value of sc1 is 3.45
(if (not sc1)(setq sc1 3.45))
(if (setq ans (getreal (strcat "\nSC1 <" (rtos sc1 2 2) ">: ")))
(setq sc1 ans)
)
And if you want to hold its latest value between drawings in one AutoCad session, use the vl-bb-set and vl-bb-ref functions, or write its value to a default file or into the registry.
There's a way to offer the previous setting as default if it exists, without that temporary [in this case 'ans'] variable, and even to incorporate an initial default value for Enter even on first use without presetting it if it doesn't exist yet, as done above, and all within one (setq) function. Let's say you want to offer an initial default of 100 if a value has not yet been set for sc1:
(setq sc1
(cond
( (getreal ; User input
(strcat
"\n* Enter Plot Scale <"
(if sc1 (rtos sc1 2 2) "100.00"); offer prior value as default if it exists, otherwise offer 100
">: "
); strcat
); getreal
); end User-input condition [returns nil on Enter, going on to:]
(sc1); Enter on subsequent use -- use prior value [nil if there isn't one, going on to:]
(100.0); Enter on first use -- no prior value; use initial default
); cond
); setq
An Environment Variable [via (setenv) / (getenv)] is another way to preserve the value across multiple editing sessions of the same drawing, and apply the same one across multiple drawings without having to set it in each. But if it's a plot scale, presumably you wouldn't want it applied at the same value in all drawings.
Other considerations:
Since sc1 is a plot scale, might it be extractable from something like the DIMSCALE System Variable, rather than having to ask the User for it?
Is there any reason not to simplify the calculations for the sc2 and th variables? [It seems odd to multiply something by 1.] Adjusting from Post 9:
(if (not sc1)
(setq
sc1 (getreal "\n* Enter Plot Scale : ")
sc2 (/ sc1 200)
th (/ sc1 500)
); setq
); if
Those divisors can be integers [not like the original 1000.0 with decimal], since sc1 will be a real number. Which raises the question: would sc1 always be a whole number [which seems likely for plot scales]? If so, should it use (getint) instead? If changed to that, the offered default in the (cond) above should be:
(if sc1 (itoa sc1) "100"); offer prior value as default if it exists, otherwise offer 100
and the Enter-on-first-use default should be:
(100); Enter on first use -- no prior value; use initial default
and those divisors in calculating sc2 and th should both be real numbers, or at some scales the sc2 and th values will come out wrong.
Kent Cooper, AIA
I don't see anything obvious that would prevent the command name from being recognized, but I'll take a shot in the dark: Could it be that a space is required after the command name and before the arguments/local-variables list's opening left parenthesis? I've always done that, and that's typically what I see in other people's code, though I don't know whether it's required. But maybe it's trying to use WSH( as the command name, and then the following syntax is incorrect.
Internally, is the Insert command completed by something in the (spot) or (cross) or (pstext) function? And that 1000,1000 should be in double-quotes [or done as a list]. If it's not being completed, and even with that incorrect point-input format, I would expect that to cause a different error, but it should at least recognize the command name, and hit an error only when you run the command.
[In answer to your earlier question, my preference is two spaces per indentation level. Tabs take up too much space for my taste, and one space doesn't make an obvious-enough difference.]
Kent Cooper, AIA