Dotted-pair detection

JGa

Hello,
in AutoLisp: how to test whether a list is of dotted-pair type?
Thank you in advance. Best regards -
Honza

Roy Klein Gebbinck

It depends on the definition of 'dotted pair':
; (KGA_List_DottedPair_P '(0 . 1)) => T ; (KGA_List_DottedPair_P '((0 1 2 3) . 0)) => T ; (KGA_List_DottedPair_P '(1 2 . 3)) => nil ; (KGA_List_DottedPair_P '(nil . 1)) => T (defun KGA_List_DottedPair_P (anyLst) (not (listp (cdr anyLst))) ) ; (KGA_List_DottedPairSimple_P '(0 . 1)) => T ; (KGA_List_DottedPairSimple_P '((0 1 2 3) . 0)) => nil ; (KGA_List_DottedPairSimple_P '(1 2 . 3)) => nil ; (KGA_List_DottedPairSimple_P '(nil . 1)) => nil (defun KGA_List_DottedPairSimple_P (anyLst) (and (not (listp (car anyLst))) (not (listp (cdr anyLst))) ) )

MP_

Different spin on an old post ...

(defun mpx-dotted-pair-p ( x ) 
    (and
        (listp x)
        (not (vl-list-length x))
    )
)

Test it:

(foreach x

   '(
        (0 . 1) 
        ((0 1 2 3) . 0)
        (1 2 . 3)
        (nil . 1)
        (10 0.0 0.0 0.0)
        (tate 42)
        42
        nil
    )

    (princ 
        (strcat 
            "\n(mpx-dotted-pair-p "
            (vl-prin1-to-string x) 
            ") >> "
            (if (mpx-dotted-pair-p x) "t" "nil")
        )
    )

    (princ)    

)

Output:

(mpx-dotted-pair-p (0 . 1))          >> t
(mpx-dotted-pair-p ((0 1 2 3) . 0))  >> t
(mpx-dotted-pair-p (1 2 . 3))        >> t
(mpx-dotted-pair-p (NIL . 1))        >> t
(mpx-dotted-pair-p (10 0.0 0.0 0.0)) >> nil
(mpx-dotted-pair-p (TATE 42))        >> nil
(mpx-dotted-pair-p 42)               >> nil
(mpx-dotted-pair-p nil)              >> nil

Cheers.

Michael.