Last point in a lisp

hi

i am very new to lisps

i only started looking at them today

and i am wondering how to use the last selected point

so i draw a line which is simple but how do i select one more point and it draws a line from the end of the first line to the new point and keep doing this for any number of points

Thanx for the help

if i havnt explain very well i will post what i have so far

Well, there are a couple of ways you could accomplish this:

Easiest being:

(command "_line")
(while (> (getvar "CMDACTIVE") 0) (command pause))

But to just retrieve the last point clicked:

(getvar "lastpoint")

and also take a look at getpoint

(setq P1 (getpoint "\npick a point: "))

thanx lee max

that was exactly what i was looking for

the only thing now is my command will not finish unless i press esc ( it doesnt finish when i press return) any help on this wld be apreciated

Could you post your routine, and I shall check for errors - the code I posted should stop if enter is pressed.

i cant post it as an attachment for some reason my work computer wnt let me but here is the text i have

(defun c:3point ()

; define the function

(setq a (getpoint "\nEnter First Point : "))

; get the first point

(setq b (getpoint "\nEnter Next Point : "))

;get the second point

(command "line" a b "")

;draw the line

(while

(setq c (getvar "lastpoint"))

(setq d (getpoint "\nEnter Next Point : "))

(command "line" c d "")

;draw the line

)

(princ)

;clean running

) ;end defun

(princ)

;clean loading

By the way the reason for this is to learn a bit about lisps and not actually something practical at the moment (hence y it is basically a line command )

I would just simplify it to this:

(defun c:3point     ()
 (command "_line")
 (while (> (getvar "CMDACTIVE") 0)
   (command pause))
 (princ))

thanks a lot lee mac

jus one thing could you pleasse explain the "while " part of the lips and the "command pause" as i have no idea what they do and i am aiming be able to write my own.

thanx again tho a big insight i had a lot of stuff ireally didnt need

Not a problem - if you still have questions, just ask

(defun c:3point     ()
 ; Define the Function - no local variables or arguments in this one, so nothing in the brackets
 (command "_line")
 ; Invoke the Line command (merely prints "line" to the command line.
 (while
 ; While the following is true
   (> (getvar "CMDACTIVE") 0)
   ; The variable "CMDACTIVE" determines whether a command is active or not, i.e, while the line command
   ; is active...
   (command pause))
 ; print a "pause" to the command line (hence pause for user input.
 (princ))
;; exit cleanly.

just out of interest on this one

how can a command be inactive

surely if it is inactive it isnt doing anyhting ??

thanx

just out of interest on this one

how can a command be inactive

 

surely if it is inactive it isnt doing anyhting ??

 

thanx

Exactly - I invoke the line command, then, while the line command is still prompting for points - i.e. it is active, I print a pause to the command line., Until the user doesn't supply a point and hence the command finishes and is inactive.