@Override
public Item item(final QueryContext ctx, final InputInfo ii) throws QueryException {
final Item a = expr[0].item(ctx, info);
if (a == null) return null;
final Item b = expr[1].item(ctx, info);
if (b == null) return null;
return calc.ev(info, a, b);
}
@Override
public Expr optimize(final QueryContext ctx, final VarScope scp) throws QueryException {
final SeqType s0 = expr[0].type();
final SeqType s1 = expr[1].type();
final Type t0 = s0.type;
final Type t1 = s1.type;
if (t0.isNumberOrUntyped() && t1.isNumberOrUntyped()) {
final Occ occ = s0.one() && s1.one() ? Occ.ONE : Occ.ZERO_ONE;
type = SeqType.get(Calc.type(t0, t1), occ);
} else if (s0.one() && s1.one()) {
type = SeqType.ITEM;
}
return optPre(oneIsEmpty() ? null : allAreValues() ? item(ctx, info) : this, ctx);
}