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Refactor threeway compare operator #71

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Merged
wusatosi merged 4 commits into from
May 10, 2025
Merged

Refactor threeway compare operator #71

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b762611
Update compare operator
20162026 May 6, 2025
5cba529
Update threeway compare
20162026 May 8, 2025
8a1c213
Cleanup threeway compare
20162026 May 8, 2025
bd6d91f
Remove equality requirement from threeway compare
20162026 May 8, 2025
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3 changes: 1 addition & 2 deletions include/beman/inplace_vector/inplace_vector.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1009,8 +1009,7 @@ struct inplace_vector

constexpr friend auto operator<=>(const inplace_vector &x,
const inplace_vector &y)
requires(std::equality_comparable<T> &&
beman::details::inplace_vector::lessthan_comparable<T>)
requires(beman::details::inplace_vector::lessthan_comparable<T>)
{
if constexpr (std::three_way_comparable<T>) {
return std::lexicographical_compare_three_way(x.begin(), x.end(),
Expand Down
72 changes: 42 additions & 30 deletions tests/beman/inplace_vector/compare.test.cpp
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Expand Up @@ -11,6 +11,10 @@ concept has_threeway = requires(const T &t) {
{ t <=> t };
};

template <class T>
concept lessthan_comparable =
beman::details::inplace_vector::lessthan_comparable<T>;
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@JeffGarland JeffGarland May 9, 2025

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It strikes me that the namespace is backwards here -- should be beman::inplace_vector::detail -- but that's an existing issue of course. And maybe something we don't address clearly in the standard.

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@wusatosi wusatosi May 9, 2025

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I might be wrong here, but beman::inplace_vector clashes with the inplace_vector struct under the beman namespace.


template <typename T> struct vec_list {
T empty;
T base; // base
Expand All @@ -25,7 +29,7 @@ template <typename T> struct vec_list {

template <typename T> static void runtests(vec_list<T> &list) {

static_assert(std::three_way_comparable<T>);
static_assert(std::three_way_comparable<T> || lessthan_comparable<T>);

// if T::value_type is threewaycomparable with ordering X then T must also
// be comparable with ordering X
Expand All @@ -41,8 +45,10 @@ template <typename T> static void runtests(vec_list<T> &list) {
if constexpr (std::three_way_comparable<VT, std::partial_ordering>)
static_assert(std::three_way_comparable<T, std::partial_ordering>);

EXPECT_TRUE(list.empty == list.empty);
EXPECT_TRUE(list.empty != list.base);
if constexpr (std::equality_comparable<VT>) {
EXPECT_TRUE(list.empty == list.empty);
EXPECT_TRUE(list.empty != list.base);
}

EXPECT_TRUE((list.base <=> list.copy) == 0);
EXPECT_TRUE((list.base <=> list.greater) < 0);
Expand All @@ -54,15 +60,23 @@ template <typename T> static void runtests(vec_list<T> &list) {
EXPECT_TRUE((list.base <=> list.greater_smaller) < 0);
EXPECT_TRUE((list.base <=> list.lesser_bigger) > 0);

EXPECT_TRUE(list.base == list.copy);
if constexpr (std::equality_comparable<VT>) {
EXPECT_TRUE(list.base == list.copy);
EXPECT_TRUE(list.base != list.greater);
EXPECT_TRUE(list.base != list.lesser);
}
EXPECT_TRUE(list.base <= list.copy);
EXPECT_TRUE(list.base >= list.copy);
EXPECT_TRUE(list.base < list.greater);
EXPECT_TRUE(list.base <= list.greater);
EXPECT_TRUE(list.base > list.lesser);
EXPECT_TRUE(list.base >= list.lesser);

EXPECT_TRUE(list.copy == list.base);
if constexpr (std::equality_comparable<VT>) {
EXPECT_TRUE(list.copy == list.base);
EXPECT_TRUE(list.copy != list.greater);
EXPECT_TRUE(list.copy != list.lesser);
}
EXPECT_TRUE(list.copy <= list.base);
EXPECT_TRUE(list.copy >= list.base);
EXPECT_TRUE(list.greater > list.base);
Expand Down Expand Up @@ -101,6 +115,25 @@ TEST(Compare, threeway_float) {
};

runtests(list);

// compare unorderable values

EXPECT_EQ(std::nanf("") <=> std::nanf(""), std::partial_ordering::unordered);
EXPECT_FALSE(std::nanf("") == std::nanf(""));
EXPECT_FALSE(std::nanf("") < std::nanf(""));
EXPECT_FALSE(std::nanf("") > std::nanf(""));
EXPECT_FALSE(std::nanf("") >= std::nanf(""));
EXPECT_FALSE(std::nanf("") <= std::nanf(""));

inplace_vector<float, 4> vnan{std::nanf("")};
inplace_vector<float, 4> vnan2{std::nanf("")};

EXPECT_EQ(vnan <=> vnan2, std::partial_ordering::unordered);
EXPECT_FALSE(vnan == vnan2);
EXPECT_FALSE(vnan < vnan2);
EXPECT_FALSE(vnan > vnan2);
EXPECT_FALSE(vnan >= vnan2);
EXPECT_FALSE(vnan <= vnan2);
}

TEST(Compare, threeway_comparable1) {
Expand Down Expand Up @@ -135,14 +168,15 @@ TEST(Compare, threeway_comparable2) {
struct comparable2 {
int a;
int b;
constexpr bool operator==(const comparable2 &) const = default;
constexpr bool operator==(const comparable2 &) const = delete;
constexpr bool operator<(const comparable2 &other) const {
return a < other.a || (a == other.a && b < other.b);
};
};

static_assert(!std::three_way_comparable<comparable2>);
static_assert(!has_threeway<comparable2>);
static_assert(lessthan_comparable<comparable2>);
static_assert(std::three_way_comparable<inplace_vector<comparable2, 4>>);
static_assert(has_threeway<inplace_vector<comparable2, 4>>);

Expand All @@ -159,25 +193,6 @@ TEST(Compare, threeway_comparable2) {
};

runtests(list);

// compare unorderable values

EXPECT_EQ(std::nanf("") <=> std::nanf(""), std::partial_ordering::unordered);
EXPECT_FALSE(std::nanf("") == std::nanf(""));
EXPECT_FALSE(std::nanf("") < std::nanf(""));
EXPECT_FALSE(std::nanf("") > std::nanf(""));
EXPECT_FALSE(std::nanf("") >= std::nanf(""));
EXPECT_FALSE(std::nanf("") <= std::nanf(""));

inplace_vector<float, 4> vnan{std::nanf("")};
inplace_vector<float, 4> vnan2{std::nanf("")};

EXPECT_EQ(vnan <=> vnan2, std::partial_ordering::unordered);
EXPECT_FALSE(vnan == vnan2);
EXPECT_FALSE(vnan < vnan2);
EXPECT_FALSE(vnan > vnan2);
EXPECT_FALSE(vnan >= vnan2);
EXPECT_FALSE(vnan <= vnan2);
}

TEST(Compare, threeway_strong_ordering) {
Expand Down Expand Up @@ -301,14 +316,11 @@ TEST(Compare, threeway_uncomparable) {

struct uncomparable3 {
int a;
constexpr auto operator<=>(const uncomparable3 &) const {
return std::partial_ordering::unordered;
}
constexpr bool operator==(const uncomparable3 &) const = delete;
constexpr auto operator<=>(const uncomparable3 &) const = delete;
};

static_assert(!std::three_way_comparable<uncomparable3>);
static_assert(has_threeway<uncomparable3>); // has <=> but no == operator
static_assert(!has_threeway<uncomparable3>);
static_assert(!std::three_way_comparable<inplace_vector<uncomparable3, 4>>);
static_assert(!has_threeway<inplace_vector<uncomparable3, 4>>);
}