Hi Konrad,
> (set 'A (1 2 3 4))
> (set 'B (cdr A))
> ...
> (set (cdr A) NIL)
The 'set' function puts a value into the CAR part of a cell (no matter
whether this is a list cell or a symbol).
A B
| |
V V
+-----+-----+ +-----+-----+ +-----+-----+ +-----+-----+
| 1 | ---+---> | 2 | ---+---> | 3 | / |---> | 4 | / |
+-----+-----+ +-----+-----+ +-----+-----+ +-----+-----+
^
|
(cdr A)
So 'set' receives the cell which is pointed to by 'B', and stores 'NIL'
into its value cell.
What you want to achieve is
A B
| |
V V
+-----+-----+ +-----+-----+ +-----+-----+ +-----+-----+
| 1 | / | | 2 | ---+---> | 3 | / |---> | 4 | / |
+-----+-----+ +-----+-----+ +-----+-----+ +-----+-----+
i.e. storing NIL into the CDR part of the first cell of 'A'.
'set' cannot do this, but 'con' stores a value in the CDR part of a cell:
: (con A NIL)
-> NIL
: A
-> (1)
: B
-> (2 3 4)
> the goal is to take a list build by fifo and turn it into a normal
> list starting at the 2nd element.
>
> so instead of (4 1 2 3 .)
> I get (1 2 3 4)
You were on the right way:
: A
-> (4 1 2 3 .)
: (setq L (cdr A))
-> (1 2 3 4 .)
: (con A NIL)
-> NIL
: L
-> (1 2 3 4)
: A
-> (4)
Cheers,
- Alex
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