ls9-list.nw

Some useful list functions

<<ls9 macros>>=
#define reverse(n) reconc((n), NIL)
#define nreverse(n) nreconc((n), NIL)
@

<<ls9 impl>>=
full reconc(full n, full m) {
	while (n != NIL) {
		if (atomp(n)) error("reconc: dotted list", n);
                m = cons(car(n), m);
		n = cdr(n);
        }
        return m;
}

full nreconc(full n, full m) {
	full	h;

	while (n != NIL) {
		if (atomp(n)) error("nreconc: dotted list", n);
		h = cdr(n);
		cdr(n) = m;
		m = n;
		n = h;
	}
	return m;
}

full conc(full a, full b) {
	full	n;

	a = reverse(a);
	protect(a);
	n = b;
	while (a != NIL) {
		n = cons(car(a), n);
		a = cdr(a);
	}
	unprot(1);
	return n;
}

full nconc(full a, full b) {
	full	n;

	n = a;
	if (NIL == a) return b;
	while (cdr(a) != NIL) a = cdr(a);
	cdr(a) = b;
	return n;
}
@