| 37 | } |
| 38 | |
| 39 | @Override |
| 40 | protected Expr opt(final CompileContext cc) throws QueryException { |
| 41 | final Expr input = arg(0); |
| 42 | final SeqType st = input.seqType(); |
| 43 | if(st.zero()) return input; |
| 44 | |
| 45 | // for the following optimizations, the numeric properties must either be static or absent |
| 46 | final IntPredicate value = e -> !defined(e) || arg(e) instanceof Value; |
| 47 | if(value.test(1) && value.test(2) && value.test(3)) { |
| 48 | final long size = input.size(); |
| 49 | if(size != -1) { |
| 50 | final Slice slice = slice(size, cc.qc); |
| 51 | if(slice.step == 1) { |
| 52 | // slice(E, 2) → util:range(E, 2) |
| 53 | // slice(TEN, 2, 1) → util:range(reverse(TEN), 9, 10) |
| 54 | final Expr arg = slice.reverse ? cc.function(REVERSE, info, input) : input; |
| 55 | return cc.function(_UTIL_RANGE, info, arg, Itr.get(slice.start), Itr.get(slice.end)); |
| 56 | } |
| 57 | } |
| 58 | // input size is unknown: exact range cannot be computed, check original properties |
| 59 | final long start = toLong(1, 1, cc.qc), end = toLong(2, Long.MAX_VALUE, cc.qc); |
| 60 | if(end == Long.MAX_VALUE && toLong(3, 1, cc.qc) == 1) { |
| 61 | // slice(E, -1) → foot(E) |
| 62 | if(start == -1) return cc.function(FOOT, info, input); |
| 63 | // slice(E, 1) → E |
| 64 | if(start == 0 || start == 1) return input; |
| 65 | // no rewritings possible for greater start values (slice always returns last item) |
| 66 | } |
| 67 | } |
| 68 | |
| 69 | exprType.assign(st.union(Occ.ZERO)).data(input); |
| 70 | return this; |
| 71 | } |
| 72 | |
| 73 | /** |
| 74 | * Returns slice properties. |