Hi again,

 > (length '(de *Day . (Mon Tue Wed Thu Fri Sat Sun .)))
 Why does 'length' have such problems here?

Circular lists are generally rather dangerous. PicLisp supports (kind of
;-) only what I would call "primary circular lists", i.e. lists that
circulate back to the first cell

I understand. I've now lowered my standards a bit. Instead of using the 'length' function, I've written a new function 'longer' that works OK, like this:

# Returns N+1 if Lst is longer than N, otherwise NIL
(de longer (Lst N)
        (for (I . X) Lst
                (T (> I N) I)
                NIL) )

# Checking a function/structure already in memory
(de ifwarn (Prg)
        (when (and (lst? Prg) (not (longer Prg 100)))
                (when (and (= (car Prg) 'if) (<> (length Prg) 4))
                        (println Prg) )
                (mapcar ifwarn Prg)
                NIL) )

# Checking a file (.l or other)
(de ifwarnfile (Path)
        (in Path (while (read) (ifwarn @))) )

As you can see, I now use 'read' (instead of 'str' as I did earlier). However, even 'read' seems not to be "bullet proof", as can be seen here:

(ifwarnfile "rcsim/lib.l")
: (ifwarnfile "rcsim/lib.l")
[rcsim/lib.l:42] !? (MUL X VX)
MUL -- Undefined
I guess the trouble could be the backquotes in this line:

(+ `(MUL X VX) `(MUL Y VY))



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