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range: Extract bound comparators

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This commit is contained in:
Tomasz Grabiec
2015-11-05 17:55:15 +01:00
committed by Asias He
parent f37512d1f7
commit 48c7f51966
1 changed files with 34 additions and 17 deletions
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51
range.hh
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@@ -61,6 +61,36 @@ public:
, _singular(true)
{ }
range() : range({}, {}) {}
private:
// Bound wrappers for compile-time dispatch and safety.
struct start_bound_ref { const optional<bound>& b; };
struct end_bound_ref { const optional<bound>& b; };
start_bound_ref start_bound() const { return { start() }; }
end_bound_ref end_bound() const { return { end() }; }
template<typename Comparator>
static bool greater_than_or_equal(end_bound_ref end, start_bound_ref start, Comparator&& cmp) {
return !end.b || !start.b || cmp(end.b->value(), start.b->value())
>= (!end.b->is_inclusive() || !start.b->is_inclusive());
}
template<typename Comparator>
static bool less_than(end_bound_ref end, start_bound_ref start, Comparator&& cmp) {
return !greater_than_or_equal(end, start, cmp);
}
template<typename Comparator>
static bool less_than_or_equal(start_bound_ref first, start_bound_ref second, Comparator&& cmp) {
return !first.b || (second.b && cmp(first.b->value(), second.b->value())
<= -(!first.b->is_inclusive() && second.b->is_inclusive()));
}
template<typename Comparator>
static bool greater_than_or_equal(end_bound_ref first, end_bound_ref second, Comparator&& cmp) {
return !first.b || (second.b && cmp(first.b->value(), second.b->value())
>= (!first.b->is_inclusive() && second.b->is_inclusive()));
}
public:
// the point is before the range (works only for non wrapped ranges)
// Comparator must define a total ordering on T.
@@ -122,17 +152,8 @@ public:
return true;
}
// check if end is greater than or equal to start, taking into account if either is inclusive.
auto greater_than_or_equal = [cmp] (const optional<bound>& end, const optional<bound>& start) {
// !start means -inf, whereas !end means +inf
if (!end || !start) {
return true;
}
return cmp(end->value(), start->value())
>= (!end->is_inclusive() || !start->is_inclusive());
};
return greater_than_or_equal(end(), other.start()) && greater_than_or_equal(other.end(), start());
return greater_than_or_equal(end_bound(), other.start_bound(), cmp)
&& greater_than_or_equal(other.end_bound(), start_bound(), cmp);
}
static range make(bound start, bound end) {
return range({std::move(start)}, {std::move(end)});
@@ -215,12 +236,8 @@ public:
}
if (!this_wraps && !other_wraps) {
return (!start() || (other.start()
&& cmp(start()->value(), other.start()->value())
<= -(!start()->is_inclusive() && other.start()->is_inclusive())))
&& (!end() || (other.end()
&& cmp(end()->value(), other.end()->value())
>= (!end()->is_inclusive() && other.end()->is_inclusive())));
return less_than_or_equal(start_bound(), other.start_bound(), cmp)
&& greater_than_or_equal(end_bound(), other.end_bound(), cmp);
}
if (other_wraps) { // && !this_wraps