oldk1331 wrote:
>
> concat!(x : %, y : %) ==
> Qnull x =>
> Qnull y => x
> Qpush(first y, x)
> QRPLACD(x, rest y)$Lisp
> x
> z := x
> while not Qnull Qrest z repeat
> z := Qrest z
> QRPLACD(z, y)$Lisp
> x
>
> First, if x is null, then Qpush and QRPLACD on x will have no effect.
> (3) -> x:=[]::List PI; concat!(x,[1]); x
>
> (3) []
No:
(5) -> ll := concat!([]$List(Integer), [1, 2, -3])
(5) [1,2,- 3]
Type: List(Integer)
Qpush is a macro, so it assigns new value to x. It seems that
we should simply have:
Qnull x => y
For some reason somebody wanted to allocate fresh node for result,
but I see no reason to do this.
>
> Second, the while loop is just 'tail'.
>
> Finally, the whole function can just be replaced by
> NCONC(x,y)$Lisp
AFAICS:
1) this would be only place in algebra using NCONC
2) Spad code adds type declarations while Lisp NCONC needs
to perform some runtime type checking, so Spad
version should be more efficient (I do not know if
it is, acutal efficiency depends on quality of Spad
and Lisp compilers).
I think is is enough reasons to roll our own version.
--
Waldek Hebisch
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