draw polyline on selected layer; help

[ReachAndre]

Hello all,
I have created a lisp that will begin a ployline on a certain layer depending on the point selected. Since my lisping skills leave something to be desired, I ask you all to take a look at this and let me know if you see a way of improving the function.

Thanks all,
Andre

;Draw polyline on selected layer
(defun drawpolyline (/ sp)
  (setq prevlay (getvar "clayer"))
  (setq sp (getpoint "\nSpecify start point: "))
  (command "_ai_molc" sp)
  (if
    (= (strcase (getvar "clayer")) "X-ANNO-BASE")
    (setvar "clayer" prevlay)
    )

  (if
    (= (strcase (getvar "clayer")) "M-SUPP-DIFF")
    (setvar "clayer" "M-SUPP-DUCT")
    )

  (if
    (= (strcase (getvar "clayer")) "M-RETN-DIFF")
    (setvar "clayer" "M-RETN-DUCT")
    )

  (if
    (= (strcase (getvar "clayer")) "M-EXHS-DIFF")
    (setvar "clayer" "M-EXHS-DUCT")
    )
  
  (command ".pline" sp)
  (princ)
  )
(defun c:dr () (drawpolyline))

[RobertB]

Yes. Use (cond) instead of multiple (if) statements.

[ReachAndre]

Hey, thats pretty useful for lisp clean up
Thank you =)

;Version II
;Draw polyline on selected layer
(defun drawpolyline (/ sp)
  (setq prevlay (getvar "clayer"))
  (setq sp (getpoint "\nSpecify start point: "))
  (command "_ai_molc" sp)

  (cond
    ((= (strcase (getvar "clayer")) "X-ANNO-BASE")
     (setvar "clayer" prevlay))    
    ((= (strcase (getvar "clayer")) "M-SUPP-DIFF")
     (setvar "clayer" "M-SUPP-DUCT"))
    ((= (strcase (getvar "clayer")) "M-RETN-DIFF")
     (setvar "clayer" "M-RETN-DUCT"))
    ((= (strcase (getvar "clayer")) "M-EXHS-DIFF")
     (setvar "clayer" "M-EXHS-DUCT"))
    )
  (command ".pline" sp)
  (princ)
  )

(defun c:dr () (drawpolyline))

[rkmcswain]

  (cond
    ((= (strcase (getvar "clayer")) "X-ANNO-BASE")
     (setvar "clayer" prevlay))    
    ((= (strcase (getvar "clayer")) "M-SUPP-DIFF")
     (setvar "clayer" "M-SUPP-DUCT"))
    ((= (strcase (getvar "clayer")) "M-RETN-DIFF")
     (setvar "clayer" "M-RETN-DUCT"))
    ((= (strcase (getvar "clayer")) "M-EXHS-DIFF")
     (setvar "clayer" "M-EXHS-DUCT"))

Another thing....
Set a variable for (strcase (getvar "clayer")) instead of calling it multiple times.

[ReachAndre]

Are you suggesting I do something like this?

;Draw polyline on selected layer Version III
(defun drawpolyline (/ sp)
  (setq prevlay (getvar "clayer"))
  (setq sp (getpoint "\nSpecify start point: "))
  (command "_ai_molc" sp)
  (setq runlay (strcase (getvar "clayer")))
  (cond
    ((= runlay "X-ANNO-BASE")
     (setvar "clayer" prevlay))
    
    ((= runlay "M-SUPP-DIFF")
     (setvar "clayer" "M-SUPP-DUCT"))

    ((= runlay "M-RETN-DIFF")
     (setvar "clayer" "M-RETN-DUCT"))

    ((= runlay "M-EXHS-DIFF")
     (setvar "clayer" "M-EXHS-DUCT"))
    )
  (command ".pline" sp)
  (princ)
  )
(defun c:DR    () (drawpolyline))

[rkmcswain]

Are you suggesting I do something like this?

Yes. It's not a big deal in this small routine, but in large programs you typically want to avoid making the same call more than once if you can save it to a variable.

[ReachAndre]

I agree, that helps clean up my prgramming, I plan to rewrite a few of my lisps that are larger so that they may be as simple.