[Orgmode] I do not understand this error

[Cecil Westerhof]

I have the following table:
        
|---+------------+---------+---------+--------+--------+-------+-------------------+----------+--------|
        |   |      datum | kmstand | prijs/l | liters | dagen  | prijs | km's   
           | prijs/km |   km/l |
        
|---+------------+---------+---------+--------+--------+-------+-------------------+----------+--------|
        | # |            |  155111 |         |        |        |       |        
           |          |        |
        | # | 2007-07-09 |  156146 |   102.2 |  62.25 | #ERROR | 63.62 | 1035   
           |    6.147 | 16.627 |
        | # | 2007-09-11 |    6953 |    97.8 |  47.75 | #ERROR | 46.70 | 
Verkeerde kmstand |          |        |
        | # |            |         |         |        | #ERROR |       |        
           |          |        |
        
|---+------------+---------+---------+--------+--------+-------+-------------------+----------+--------|
        #+TBLFM: $6='(if (and (not (check-if-after-hline)) (nz @-1$2) (nz $2)) 
(-  (time-to-days (org-read-date t t "$2")) (time-to-days (org-read-date t t 
"@-1$2"))) "");S::$7='(if (and (nz $4) (nz $5)) (format "%.2f" (/ (* $4 $5) 
100)) "");N::$8='(if (and (nz @-1$3) (nz $3)) (if (> $3 @-1$3) (- $3 @-1$3) (if 
(not (check-if-after-hline)) "Verkeerde kmstand" "")) "");N::$9='(if (and (nz 
$8) (nz $7)) (format "%.3f" (/ (* $7 100) $8)) "");N::$10='(if (and (nz $8) (nz 
$5)) (format "%.3f" (/ $8 $5)) "");N

With debug I get:
        Substitution history of formula
        Orig:   '(if (and (not (check-if-after-hline)) (nz @-1$2) (nz $2)) (-  
(time-to-days (org-read-date t t "$2")) (time-to-days (org-read-date t t 
"@-1$2"))) "");S
        $xyz->  '(if (and (not (check-if-after-hline)) (nz @-1$2) (nz $2)) (-  
(time-to-days (org-read-date t t "$2")) (time-to-days (org-read-date t t 
"@-1$2"))) "")
        @r$c->  '(if (and (not (check-if-after-hline)) (nz #("            " 0 
12 (lazy-lock t face org-table hilit-chg hilit-chg))) (nz $2)) (-  
(time-to-days (org-read-date t t "$2")) (time-to-days (org-read-date t t "#("   
         " 0 12 (lazy-lock t face org-table hilit-chg hilit-chg))"))) "")
        $1->    '(if (and (not (check-if-after-hline)) (nz #("            " 0 
12 (lazy-lock t face org-table hilit-chg hilit-chg))) (nz #("2007-07-09" 0 3 
(hilit-chg hilit-chg lazy-lock t) 3 5 (hilit-chg hilit-chg lazy-lock t) 5 6 
(hilit-chg hilit-chg lazy-lock t) 6 8 (hilit-chg hilit-chg lazy-lock t) 8 9 
(hilit-chg hilit-chg lazy-lock t) 9 10 (hilit-chg hilit-chg lazy-lock t)))) (-  
(time-to-days (org-read-date t t "#("2007-07-09" 0 3 (hilit-chg hilit-chg 
lazy-lock t) 3 5 (hilit-chg hilit-chg lazy-lock t) 5 6 (hilit-chg hilit-chg 
lazy-lock t) 6 8 (hilit-chg hilit-chg lazy-lock t) 8 9 (hilit-chg hilit-chg 
lazy-lock t) 9 10 (hilit-chg hilit-chg lazy-lock t))")) (time-to-days 
(org-read-date t t "#("            " 0 12 (lazy-lock t face org-table hilit-chg 
hilit-chg))"))) "")
        Result: #ERROR
        Format: NONE
        Final:  #ERROR
If I use the code after $1, I get:
        Debugger entered--Lisp error: (wrong-type-argument number-or-marker-p 
#("            " 0 12 (lazy-lock t face org-table hilit-chg hilit-chg)))
          =(#("            " 0 12 (lazy-lock t face org-table hilit-chg 
hilit-chg)) 0)
          (not (= n 0))
          nz(#("            " 0 12 (lazy-lock t face org-table hilit-chg 
hilit-chg)))
          (and (not (check-if-after-hline)) (nz #("            " 0 12 ...)) (nz 
#("2007-07-09" 0 3 ... 3 5 ... 5 6 ... 6 8 ... 8 9 ... 9 10 ...)))
          (if (and (not ...) (nz #("            " 0 12 ...)) (nz #("2007-07-09" 
0 3 ... 3 5 ... 5 6 ... 6 8 ... 8 9 ... 9 10 ...))) (- (time-to-days ...) 
(time-to-days ...)) "")
          eval((if (and (not ...) (nz #("            " 0 12 ...)) (nz 
#("2007-07-09" 0 3 ... 3 5 ... 5 6 ... 6 8 ... 8 9 ... 9 10 ...))) (- 
(time-to-days ...) (time-to-days ...)) ""))
          eval-last-sexp-1(t)
          eval-last-sexp(t)
          eval-print-last-sexp()
          call-interactively(eval-print-last-sexp)
          recursive-edit()
          byte-code(...
          debug(error (wrong-type-argument number-or-marker-p #("          " 0 
10 (lazy-lock t face org-table hilit-chg hilit-chg))))
          =(#("          " 0 10 (lazy-lock t face org-table hilit-chg 
hilit-chg)) 0)
          (not (= n 0))
          nz(#("          " 0 10 (lazy-lock t face org-table hilit-chg 
hilit-chg)))
          (and (not (check-if-after-hline)) (nz #("          " 0 10 ...)) (nz 
#("20070709" 0 3 ... 3 4 ... 4 5 ... 5 6 ... 6 7 ... 7 8 ...)))
          (if (and (not ...) (nz #("          " 0 10 ...)) (nz #("20070709" 0 3 
... 3 4 ... 4 5 ... 5 6 ... 6 7 ... 7 8 ...))) (- (time-to-days ...) 
(time-to-days ...)) "")
          eval((if (and (not ...) (nz #("          " 0 10 ...)) (nz 
#("20070709" 0 3 ... 3 4 ... 4 5 ... 5 6 ... 6 7 ... 7 8 ...))) (- 
(time-to-days ...) (time-to-days ...)) ""))
          eval-last-sexp-1(t)
          eval-last-sexp(t)
          eval-print-last-sexp()
          call-interactively(eval-print-last-sexp)
          recursive-edit()
          byte-code(...
          debug(error (void-variable nz))
          (and (not (check-if-after-hline)) nz (#("          " 0 10 ...)) (nz 
#("20070709" 0 3 ... 3 4 ... 4 5 ... 5 6 ... 6 7 ... 7 8 ...)))
          (if (and (not ...) nz (#("          " 0 10 ...)) (nz #("20070709" 0 3 
... 3 4 ... 4 5 ... 5 6 ... 6 7 ... 7 8 ...))) (- (time-to-days ...) 
(time-to-days ...)) "")
          eval((if (and (not ...) nz (#("          " 0 10 ...)) (nz 
#("20070709" 0 3 ... 3 4 ... 4 5 ... 5 6 ... 6 7 ... 7 8 ...))) (- 
(time-to-days ...) (time-to-days ...)) ""))
          eval-last-sexp-1(t)
          eval-last-sexp(t)
          eval-print-last-sexp()
          call-interactively(eval-print-last-sexp)
          recursive-edit()
          byte-code(...
          debug(error (void-variable nz))
          (and (not (check-if-after-hline)) nz (#("          " 0 10 ...)) (nz 
#("20070709" 0 3 ... 3 4 ... 4 5 ... 5 6 ... 6 7 ... 7 8 ...)))
          (if (and (not ...) nz (#("          " 0 10 ...)) (nz #("20070709" 0 3 
... 3 4 ... 4 5 ... 5 6 ... 6 7 ... 7 8 ...))) (- (time-to-days ...) 
(time-to-days ...)) "")
          eval((if (and (not ...) nz (#("          " 0 10 ...)) (nz 
#("20070709" 0 3 ... 3 4 ... 4 5 ... 5 6 ... 6 7 ... 7 8 ...))) (- 
(time-to-days ...) (time-to-days ...)) ""))
          eval-last-sexp-1(t)
          eval-last-sexp(t)
          eval-print-last-sexp()
          call-interactively(eval-print-last-sexp)
          recursive-edit()
          byte-code(...
          debug(error (wrong-type-argument integerp nil))
          decode-time((nil nil nil 9 7 2007 nil nil nil))
          time-to-day-in-year((nil nil nil 9 7 2007 nil nil nil))
          eval((time-to-day-in-year (parse-time-string "2007-07-09")))
          eval-last-sexp-1(t)
          eval-last-sexp(t)
          eval-print-last-sexp()
          call-interactively(eval-print-last-sexp)
          recursive-edit()
          byte-code(...
          debug(error (void-function parse_time_string))
          (parse_time_string "2007-07-09")
          eval((parse_time_string "2007-07-09"))
          eval-last-sexp-1(t)
          eval-last-sexp(t)
          eval-print-last-sexp()
          call-interactively(eval-print-last-sexp)

Where there stands 'byte-code(...', there was some byte-code which I could not 
copy for one reason or another.
nz is a function which checks if a field is empty (or zero). And this
does not give a problem in the other columns.
So what am I doing wrong?

To be sure, here is the code of nz:
        ;;; notZero
        (defun nz (n)
          (interactive "nValue: ")
          (not (= n 0.))
        )

-- 
Cecil Westerhof <address@hidden>