libcxx/test/std/language.support/cmp/cmp.alg/strong_order.pass.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 // UNSUPPORTED: c++03, c++11, c++14, c++17
  10
  11 // <compare>
  12
  13 // template<class T> constexpr strong_ordering strong_order(const T& a, const T& b);
  14
  15 #include <compare>
  16
  17 #include <cassert>
  18 #include <cmath>
  19 #include <iterator> // std::size
  20 #include <limits>
  21 #include <type_traits>
  22 #include <utility>
  23
  24 #include "test_macros.h"
  25
  26 #if defined(__i386__)
  27  #define TEST_BUGGY_SIGNALING_NAN
  28 #endif
  29
  30 template<class T, class U>
  31 constexpr auto has_strong_order(T&& t, U&& u)
  32     -> decltype(std::strong_order(static_cast<T&&>(t), static_cast<U&&>(u)), true)
  33 {
  34     return true;
  35 }
  36
  37 constexpr bool has_strong_order(...) {
  38     return false;
  39 }
  40
  41 namespace N11 {
  42     struct A {};
  43     struct B {};
  44     std::strong_ordering strong_order(const A&, const A&) { return std::strong_ordering::less; }
  45     std::strong_ordering strong_order(const A&, const B&);
  46 }
  47
  48 void test_1_1()
  49 {
  50     // If the decayed types of E and F differ, strong_order(E, F) is ill-formed.
  51
  52     static_assert( has_strong_order(1, 2));
  53     static_assert(!has_strong_order(1, (short)2));
  54     static_assert(!has_strong_order(1, 2.0));
  55     static_assert(!has_strong_order(1.0f, 2.0));
  56
  57     static_assert( has_strong_order((int*)nullptr, (int*)nullptr));
  58     static_assert(!has_strong_order((int*)nullptr, (const int*)nullptr));
  59     static_assert(!has_strong_order((const int*)nullptr, (int*)nullptr));
  60     static_assert( has_strong_order((const int*)nullptr, (const int*)nullptr));
  61
  62     N11::A a;
  63     N11::B b;
  64     static_assert( has_strong_order(a, a));
  65     static_assert(!has_strong_order(a, b));
  66 }
  67
  68 namespace N12 {
  69     struct A {};
  70     std::strong_ordering strong_order(A&, A&&) { return std::strong_ordering::less; }
  71     std::strong_ordering strong_order(A&&, A&&) { return std::strong_ordering::equal; }
  72     std::strong_ordering strong_order(const A&, const A&);
  73
  74     struct B {
  75         friend std::weak_ordering strong_order(B&, B&);
  76     };
  77
  78     struct StrongOrder {
  79         explicit operator std::strong_ordering() const { return std::strong_ordering::less; }
  80     };
  81     struct C {
  82         bool touched = false;
  83         friend StrongOrder strong_order(C& lhs, C&) { lhs.touched = true; return StrongOrder(); }
  84     };
  85 }
  86
  87 void test_1_2()
  88 {
  89     // Otherwise, strong_ordering(strong_order(E, F))
  90     // if it is a well-formed expression with overload resolution performed
  91     // in a context that does not include a declaration of std::strong_order.
  92
  93     // Test that strong_order does not const-qualify the forwarded arguments.
  94     N12::A a;
  95     assert(std::strong_order(a, std::move(a)) == std::strong_ordering::less);
  96     assert(std::strong_order(std::move(a), std::move(a)) == std::strong_ordering::equal);
  97
  98     // The type of strong_order(e,f) must be explicitly convertible to strong_ordering.
  99     N12::B b;
 100     static_assert(!has_strong_order(b, b));
 101
 102     N12::C c1, c2;
 103     ASSERT_SAME_TYPE(decltype(std::strong_order(c1, c2)), std::strong_ordering);
 104     assert(std::strong_order(c1, c2) == std::strong_ordering::less);
 105     assert(c1.touched);
 106     assert(!c2.touched);
 107 }
 108
 109 template<class F>
 110 constexpr bool test_1_3()
 111 {
 112     // Otherwise, if the decayed type T of E is a floating-point type,
 113     // yields a value of type strong_ordering that is consistent with
 114     // the ordering observed by T's comparison operators,
 115     // and if numeric_limits<T>::is_iec559 is true, is additionally consistent with
 116     // the totalOrder operation as specified in ISO/IEC/IEEE 60559.
 117
 118     static_assert(std::numeric_limits<F>::is_iec559);
 119
 120     ASSERT_SAME_TYPE(decltype(std::strong_order(F(0), F(0))), std::strong_ordering);
 121
 122     F v[] = {
 123         -std::numeric_limits<F>::infinity(),
 124         std::numeric_limits<F>::lowest(),  // largest (finite) negative number
 125         F(-1.0), F(-0.1),
 126         -std::numeric_limits<F>::min(),    // smallest (normal) negative number
 127         F(-0.0),                           // negative zero
 128         F(0.0),
 129         std::numeric_limits<F>::min(),     // smallest (normal) positive number
 130         F(0.1), F(1.0), F(2.0), F(3.14),
 131         std::numeric_limits<F>::max(),     // largest (finite) positive number
 132         std::numeric_limits<F>::infinity(),
 133     };
 134
 135     static_assert(std::size(v) == 14);
 136
 137     // Sanity-check that array 'v' is indeed in the right order.
 138     for (int i=0; i < 14; ++i) {
 139         for (int j=0; j < 14; ++j) {
 140             auto naturalOrder = (v[i] <=> v[j]);
 141             if (v[i] == 0 && v[j] == 0) {
 142                 assert(naturalOrder == std::partial_ordering::equivalent);
 143             } else {
 144                 assert(naturalOrder == std::partial_ordering::unordered || naturalOrder == (i <=> j));
 145             }
 146         }
 147     }
 148
 149     assert(std::strong_order(v[0], v[0]) == std::strong_ordering::equal);
 150     assert(std::strong_order(v[0], v[1]) == std::strong_ordering::less);
 151     assert(std::strong_order(v[0], v[2]) == std::strong_ordering::less);
 152     assert(std::strong_order(v[0], v[3]) == std::strong_ordering::less);
 153     assert(std::strong_order(v[0], v[4]) == std::strong_ordering::less);
 154     assert(std::strong_order(v[0], v[5]) == std::strong_ordering::less);
 155     assert(std::strong_order(v[0], v[6]) == std::strong_ordering::less);
 156     assert(std::strong_order(v[0], v[7]) == std::strong_ordering::less);
 157     assert(std::strong_order(v[0], v[8]) == std::strong_ordering::less);
 158     assert(std::strong_order(v[0], v[9]) == std::strong_ordering::less);
 159     assert(std::strong_order(v[0], v[10]) == std::strong_ordering::less);
 160     assert(std::strong_order(v[0], v[11]) == std::strong_ordering::less);
 161     assert(std::strong_order(v[0], v[12]) == std::strong_ordering::less);
 162     assert(std::strong_order(v[0], v[13]) == std::strong_ordering::less);
 163     assert(std::strong_order(v[1], v[0]) == std::strong_ordering::greater);
 164     assert(std::strong_order(v[1], v[1]) == std::strong_ordering::equal);
 165     assert(std::strong_order(v[1], v[2]) == std::strong_ordering::less);
 166     assert(std::strong_order(v[1], v[3]) == std::strong_ordering::less);
 167     assert(std::strong_order(v[1], v[4]) == std::strong_ordering::less);
 168     assert(std::strong_order(v[1], v[5]) == std::strong_ordering::less);
 169     assert(std::strong_order(v[1], v[6]) == std::strong_ordering::less);
 170     assert(std::strong_order(v[1], v[7]) == std::strong_ordering::less);
 171     assert(std::strong_order(v[1], v[8]) == std::strong_ordering::less);
 172     assert(std::strong_order(v[1], v[9]) == std::strong_ordering::less);
 173     assert(std::strong_order(v[1], v[10]) == std::strong_ordering::less);
 174     assert(std::strong_order(v[1], v[11]) == std::strong_ordering::less);
 175     assert(std::strong_order(v[1], v[12]) == std::strong_ordering::less);
 176     assert(std::strong_order(v[1], v[13]) == std::strong_ordering::less);
 177     assert(std::strong_order(v[2], v[0]) == std::strong_ordering::greater);
 178     assert(std::strong_order(v[2], v[1]) == std::strong_ordering::greater);
 179     assert(std::strong_order(v[2], v[2]) == std::strong_ordering::equal);
 180     assert(std::strong_order(v[2], v[3]) == std::strong_ordering::less);
 181     assert(std::strong_order(v[2], v[4]) == std::strong_ordering::less);
 182     assert(std::strong_order(v[2], v[5]) == std::strong_ordering::less);
 183     assert(std::strong_order(v[2], v[6]) == std::strong_ordering::less);
 184     assert(std::strong_order(v[2], v[7]) == std::strong_ordering::less);
 185     assert(std::strong_order(v[2], v[8]) == std::strong_ordering::less);
 186     assert(std::strong_order(v[2], v[9]) == std::strong_ordering::less);
 187     assert(std::strong_order(v[2], v[10]) == std::strong_ordering::less);
 188     assert(std::strong_order(v[2], v[11]) == std::strong_ordering::less);
 189     assert(std::strong_order(v[2], v[12]) == std::strong_ordering::less);
 190     assert(std::strong_order(v[2], v[13]) == std::strong_ordering::less);
 191     assert(std::strong_order(v[3], v[0]) == std::strong_ordering::greater);
 192     assert(std::strong_order(v[3], v[1]) == std::strong_ordering::greater);
 193     assert(std::strong_order(v[3], v[2]) == std::strong_ordering::greater);
 194     assert(std::strong_order(v[3], v[3]) == std::strong_ordering::equal);
 195     assert(std::strong_order(v[3], v[4]) == std::strong_ordering::less);
 196     assert(std::strong_order(v[3], v[5]) == std::strong_ordering::less);
 197     assert(std::strong_order(v[3], v[6]) == std::strong_ordering::less);
 198     assert(std::strong_order(v[3], v[7]) == std::strong_ordering::less);
 199     assert(std::strong_order(v[3], v[8]) == std::strong_ordering::less);
 200     assert(std::strong_order(v[3], v[9]) == std::strong_ordering::less);
 201     assert(std::strong_order(v[3], v[10]) == std::strong_ordering::less);
 202     assert(std::strong_order(v[3], v[11]) == std::strong_ordering::less);
 203     assert(std::strong_order(v[3], v[12]) == std::strong_ordering::less);
 204     assert(std::strong_order(v[3], v[13]) == std::strong_ordering::less);
 205     assert(std::strong_order(v[4], v[0]) == std::strong_ordering::greater);
 206     assert(std::strong_order(v[4], v[1]) == std::strong_ordering::greater);
 207     assert(std::strong_order(v[4], v[2]) == std::strong_ordering::greater);
 208     assert(std::strong_order(v[4], v[3]) == std::strong_ordering::greater);
 209     assert(std::strong_order(v[4], v[4]) == std::strong_ordering::equal);
 210     assert(std::strong_order(v[4], v[5]) == std::strong_ordering::less);
 211     assert(std::strong_order(v[4], v[6]) == std::strong_ordering::less);
 212     assert(std::strong_order(v[4], v[7]) == std::strong_ordering::less);
 213     assert(std::strong_order(v[4], v[8]) == std::strong_ordering::less);
 214     assert(std::strong_order(v[4], v[9]) == std::strong_ordering::less);
 215     assert(std::strong_order(v[4], v[10]) == std::strong_ordering::less);
 216     assert(std::strong_order(v[4], v[11]) == std::strong_ordering::less);
 217     assert(std::strong_order(v[4], v[12]) == std::strong_ordering::less);
 218     assert(std::strong_order(v[4], v[13]) == std::strong_ordering::less);
 219     assert(std::strong_order(v[5], v[0]) == std::strong_ordering::greater);
 220     assert(std::strong_order(v[5], v[1]) == std::strong_ordering::greater);
 221     assert(std::strong_order(v[5], v[2]) == std::strong_ordering::greater);
 222     assert(std::strong_order(v[5], v[3]) == std::strong_ordering::greater);
 223     assert(std::strong_order(v[5], v[4]) == std::strong_ordering::greater);
 224     assert(std::strong_order(v[5], v[5]) == std::strong_ordering::equal);
 225     assert(std::strong_order(v[5], v[6]) == std::strong_ordering::less);
 226     assert(std::strong_order(v[5], v[7]) == std::strong_ordering::less);
 227     assert(std::strong_order(v[5], v[8]) == std::strong_ordering::less);
 228     assert(std::strong_order(v[5], v[9]) == std::strong_ordering::less);
 229     assert(std::strong_order(v[5], v[10]) == std::strong_ordering::less);
 230     assert(std::strong_order(v[5], v[11]) == std::strong_ordering::less);
 231     assert(std::strong_order(v[5], v[12]) == std::strong_ordering::less);
 232     assert(std::strong_order(v[5], v[13]) == std::strong_ordering::less);
 233     assert(std::strong_order(v[6], v[0]) == std::strong_ordering::greater);
 234     assert(std::strong_order(v[6], v[1]) == std::strong_ordering::greater);
 235     assert(std::strong_order(v[6], v[2]) == std::strong_ordering::greater);
 236     assert(std::strong_order(v[6], v[3]) == std::strong_ordering::greater);
 237     assert(std::strong_order(v[6], v[4]) == std::strong_ordering::greater);
 238     assert(std::strong_order(v[6], v[5]) == std::strong_ordering::greater);
 239     assert(std::strong_order(v[6], v[6]) == std::strong_ordering::equal);
 240     assert(std::strong_order(v[6], v[7]) == std::strong_ordering::less);
 241     assert(std::strong_order(v[6], v[8]) == std::strong_ordering::less);
 242     assert(std::strong_order(v[6], v[9]) == std::strong_ordering::less);
 243     assert(std::strong_order(v[6], v[10]) == std::strong_ordering::less);
 244     assert(std::strong_order(v[6], v[11]) == std::strong_ordering::less);
 245     assert(std::strong_order(v[6], v[12]) == std::strong_ordering::less);
 246     assert(std::strong_order(v[6], v[13]) == std::strong_ordering::less);
 247     assert(std::strong_order(v[7], v[0]) == std::strong_ordering::greater);
 248     assert(std::strong_order(v[7], v[1]) == std::strong_ordering::greater);
 249     assert(std::strong_order(v[7], v[2]) == std::strong_ordering::greater);
 250     assert(std::strong_order(v[7], v[3]) == std::strong_ordering::greater);
 251     assert(std::strong_order(v[7], v[4]) == std::strong_ordering::greater);
 252     assert(std::strong_order(v[7], v[5]) == std::strong_ordering::greater);
 253     assert(std::strong_order(v[7], v[6]) == std::strong_ordering::greater);
 254     assert(std::strong_order(v[7], v[7]) == std::strong_ordering::equal);
 255     assert(std::strong_order(v[7], v[8]) == std::strong_ordering::less);
 256     assert(std::strong_order(v[7], v[9]) == std::strong_ordering::less);
 257     assert(std::strong_order(v[7], v[10]) == std::strong_ordering::less);
 258     assert(std::strong_order(v[7], v[11]) == std::strong_ordering::less);
 259     assert(std::strong_order(v[7], v[12]) == std::strong_ordering::less);
 260     assert(std::strong_order(v[7], v[13]) == std::strong_ordering::less);
 261     assert(std::strong_order(v[8], v[0]) == std::strong_ordering::greater);
 262     assert(std::strong_order(v[8], v[1]) == std::strong_ordering::greater);
 263     assert(std::strong_order(v[8], v[2]) == std::strong_ordering::greater);
 264     assert(std::strong_order(v[8], v[3]) == std::strong_ordering::greater);
 265     assert(std::strong_order(v[8], v[4]) == std::strong_ordering::greater);
 266     assert(std::strong_order(v[8], v[5]) == std::strong_ordering::greater);
 267     assert(std::strong_order(v[8], v[6]) == std::strong_ordering::greater);
 268     assert(std::strong_order(v[8], v[7]) == std::strong_ordering::greater);
 269     assert(std::strong_order(v[8], v[8]) == std::strong_ordering::equal);
 270     assert(std::strong_order(v[8], v[9]) == std::strong_ordering::less);
 271     assert(std::strong_order(v[8], v[10]) == std::strong_ordering::less);
 272     assert(std::strong_order(v[8], v[11]) == std::strong_ordering::less);
 273     assert(std::strong_order(v[8], v[12]) == std::strong_ordering::less);
 274     assert(std::strong_order(v[8], v[13]) == std::strong_ordering::less);
 275     assert(std::strong_order(v[9], v[0]) == std::strong_ordering::greater);
 276     assert(std::strong_order(v[9], v[1]) == std::strong_ordering::greater);
 277     assert(std::strong_order(v[9], v[2]) == std::strong_ordering::greater);
 278     assert(std::strong_order(v[9], v[3]) == std::strong_ordering::greater);
 279     assert(std::strong_order(v[9], v[4]) == std::strong_ordering::greater);
 280     assert(std::strong_order(v[9], v[5]) == std::strong_ordering::greater);
 281     assert(std::strong_order(v[9], v[6]) == std::strong_ordering::greater);
 282     assert(std::strong_order(v[9], v[7]) == std::strong_ordering::greater);
 283     assert(std::strong_order(v[9], v[8]) == std::strong_ordering::greater);
 284     assert(std::strong_order(v[9], v[9]) == std::strong_ordering::equal);
 285     assert(std::strong_order(v[9], v[10]) == std::strong_ordering::less);
 286     assert(std::strong_order(v[9], v[11]) == std::strong_ordering::less);
 287     assert(std::strong_order(v[9], v[12]) == std::strong_ordering::less);
 288     assert(std::strong_order(v[9], v[13]) == std::strong_ordering::less);
 289     assert(std::strong_order(v[10], v[0]) == std::strong_ordering::greater);
 290     assert(std::strong_order(v[10], v[1]) == std::strong_ordering::greater);
 291     assert(std::strong_order(v[10], v[2]) == std::strong_ordering::greater);
 292     assert(std::strong_order(v[10], v[3]) == std::strong_ordering::greater);
 293     assert(std::strong_order(v[10], v[4]) == std::strong_ordering::greater);
 294     assert(std::strong_order(v[10], v[5]) == std::strong_ordering::greater);
 295     assert(std::strong_order(v[10], v[6]) == std::strong_ordering::greater);
 296     assert(std::strong_order(v[10], v[7]) == std::strong_ordering::greater);
 297     assert(std::strong_order(v[10], v[8]) == std::strong_ordering::greater);
 298     assert(std::strong_order(v[10], v[9]) == std::strong_ordering::greater);
 299     assert(std::strong_order(v[10], v[10]) == std::strong_ordering::equal);
 300     assert(std::strong_order(v[10], v[11]) == std::strong_ordering::less);
 301     assert(std::strong_order(v[10], v[12]) == std::strong_ordering::less);
 302     assert(std::strong_order(v[10], v[13]) == std::strong_ordering::less);
 303     assert(std::strong_order(v[11], v[0]) == std::strong_ordering::greater);
 304     assert(std::strong_order(v[11], v[1]) == std::strong_ordering::greater);
 305     assert(std::strong_order(v[11], v[2]) == std::strong_ordering::greater);
 306     assert(std::strong_order(v[11], v[3]) == std::strong_ordering::greater);
 307     assert(std::strong_order(v[11], v[4]) == std::strong_ordering::greater);
 308     assert(std::strong_order(v[11], v[5]) == std::strong_ordering::greater);
 309     assert(std::strong_order(v[11], v[6]) == std::strong_ordering::greater);
 310     assert(std::strong_order(v[11], v[7]) == std::strong_ordering::greater);
 311     assert(std::strong_order(v[11], v[8]) == std::strong_ordering::greater);
 312     assert(std::strong_order(v[11], v[9]) == std::strong_ordering::greater);
 313     assert(std::strong_order(v[11], v[10]) == std::strong_ordering::greater);
 314     assert(std::strong_order(v[11], v[11]) == std::strong_ordering::equal);
 315     assert(std::strong_order(v[11], v[12]) == std::strong_ordering::less);
 316     assert(std::strong_order(v[11], v[13]) == std::strong_ordering::less);
 317     assert(std::strong_order(v[12], v[0]) == std::strong_ordering::greater);
 318     assert(std::strong_order(v[12], v[1]) == std::strong_ordering::greater);
 319     assert(std::strong_order(v[12], v[2]) == std::strong_ordering::greater);
 320     assert(std::strong_order(v[12], v[3]) == std::strong_ordering::greater);
 321     assert(std::strong_order(v[12], v[4]) == std::strong_ordering::greater);
 322     assert(std::strong_order(v[12], v[5]) == std::strong_ordering::greater);
 323     assert(std::strong_order(v[12], v[6]) == std::strong_ordering::greater);
 324     assert(std::strong_order(v[12], v[7]) == std::strong_ordering::greater);
 325     assert(std::strong_order(v[12], v[8]) == std::strong_ordering::greater);
 326     assert(std::strong_order(v[12], v[9]) == std::strong_ordering::greater);
 327     assert(std::strong_order(v[12], v[10]) == std::strong_ordering::greater);
 328     assert(std::strong_order(v[12], v[11]) == std::strong_ordering::greater);
 329     assert(std::strong_order(v[12], v[12]) == std::strong_ordering::equal);
 330     assert(std::strong_order(v[12], v[13]) == std::strong_ordering::less);
 331     assert(std::strong_order(v[13], v[0]) == std::strong_ordering::greater);
 332     assert(std::strong_order(v[13], v[1]) == std::strong_ordering::greater);
 333     assert(std::strong_order(v[13], v[2]) == std::strong_ordering::greater);
 334     assert(std::strong_order(v[13], v[3]) == std::strong_ordering::greater);
 335     assert(std::strong_order(v[13], v[4]) == std::strong_ordering::greater);
 336     assert(std::strong_order(v[13], v[5]) == std::strong_ordering::greater);
 337     assert(std::strong_order(v[13], v[6]) == std::strong_ordering::greater);
 338     assert(std::strong_order(v[13], v[7]) == std::strong_ordering::greater);
 339     assert(std::strong_order(v[13], v[8]) == std::strong_ordering::greater);
 340     assert(std::strong_order(v[13], v[9]) == std::strong_ordering::greater);
 341     assert(std::strong_order(v[13], v[10]) == std::strong_ordering::greater);
 342     assert(std::strong_order(v[13], v[11]) == std::strong_ordering::greater);
 343     assert(std::strong_order(v[13], v[12]) == std::strong_ordering::greater);
 344     assert(std::strong_order(v[13], v[13]) == std::strong_ordering::equal);
 345
 346
 347     // There's no way to produce a specifically positive or negative NAN
 348     // at compile-time, so the NAN-related tests must be runtime-only.
 349     // Also, x86-32 (x87 floating point) cannot handle signaling NANs;
 350     // see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57484 for context.
 351
 352     if (!std::is_constant_evaluated()) {
 353         F nq = std::copysign(std::numeric_limits<F>::quiet_NaN(), F(-1));
 354         F ns = std::copysign(std::numeric_limits<F>::signaling_NaN(), F(-1));
 355         F ps = std::copysign(std::numeric_limits<F>::signaling_NaN(), F(+1));
 356         F pq = std::copysign(std::numeric_limits<F>::quiet_NaN(), F(+1));
 357
 358         assert(std::strong_order(nq, nq) == std::strong_ordering::equal);
 359 #ifndef TEST_BUGGY_SIGNALING_NAN
 360         assert(std::strong_order(nq, ns) == std::strong_ordering::less);
 361 #endif
 362         for (int i=0; i < 14; ++i) {
 363             assert(std::strong_order(nq, v[i]) == std::strong_ordering::less);
 364         }
 365         assert(std::strong_order(nq, ps) == std::strong_ordering::less);
 366         assert(std::strong_order(nq, pq) == std::strong_ordering::less);
 367
 368 #ifndef TEST_BUGGY_SIGNALING_NAN
 369         assert(std::strong_order(ns, nq) == std::strong_ordering::greater);
 370 #endif
 371         assert(std::strong_order(ns, ns) == std::strong_ordering::equal);
 372         for (int i=0; i < 14; ++i) {
 373             assert(std::strong_order(ns, v[i]) == std::strong_ordering::less);
 374         }
 375         assert(std::strong_order(ns, ps) == std::strong_ordering::less);
 376         assert(std::strong_order(ns, pq) == std::strong_ordering::less);
 377
 378         assert(std::strong_order(ps, nq) == std::strong_ordering::greater);
 379         assert(std::strong_order(ps, ns) == std::strong_ordering::greater);
 380         for (int i=0; i < 14; ++i) {
 381             assert(std::strong_order(ps, v[i]) == std::strong_ordering::greater);
 382         }
 383         assert(std::strong_order(ps, ps) == std::strong_ordering::equal);
 384 #ifndef TEST_BUGGY_SIGNALING_NAN
 385         assert(std::strong_order(ps, pq) == std::strong_ordering::less);
 386 #endif
 387
 388         assert(std::strong_order(pq, nq) == std::strong_ordering::greater);
 389         assert(std::strong_order(pq, ns) == std::strong_ordering::greater);
 390         for (int i=0; i < 14; ++i) {
 391             assert(std::strong_order(pq, v[i]) == std::strong_ordering::greater);
 392         }
 393 #ifndef TEST_BUGGY_SIGNALING_NAN
 394         assert(std::strong_order(pq, ps) == std::strong_ordering::greater);
 395 #endif
 396         assert(std::strong_order(pq, pq) == std::strong_ordering::equal);
 397     }
 398
 399     return true;
 400 }
 401
 402 namespace N14 {
 403     // Compare to N12::A.
 404     struct A {};
 405     bool operator==(const A&, const A&);
 406     constexpr std::strong_ordering operator<=>(A&, A&&) { return std::strong_ordering::less; }
 407     constexpr std::strong_ordering operator<=>(A&&, A&&) { return std::strong_ordering::equal; }
 408     std::strong_ordering operator<=>(const A&, const A&);
 409     static_assert(std::three_way_comparable<A>);
 410
 411     struct B {
 412         std::strong_ordering operator<=>(const B&) const;  // lacks operator==
 413     };
 414     static_assert(!std::three_way_comparable<B>);
 415
 416     struct C {
 417         bool *touched;
 418         bool operator==(const C&) const;
 419         constexpr std::strong_ordering operator<=>(const C& rhs) const {
 420             *rhs.touched = true;
 421             return std::strong_ordering::equal;
 422         }
 423     };
 424     static_assert(std::three_way_comparable<C>);
 425 }
 426
 427 constexpr bool test_1_4()
 428 {
 429     // Otherwise, strong_ordering(compare_three_way()(E, F)) if it is a well-formed expression.
 430
 431     // Test neither strong_order nor compare_three_way const-qualify the forwarded arguments.
 432     N14::A a;
 433     assert(std::strong_order(a, std::move(a)) == std::strong_ordering::less);
 434     assert(std::strong_order(std::move(a), std::move(a)) == std::strong_ordering::equal);
 435
 436     N14::B b;
 437     static_assert(!has_strong_order(b, b));
 438
 439     // Test that the arguments are passed to <=> in the correct order.
 440     bool c1_touched = false;
 441     bool c2_touched = false;
 442     N14::C c1 = {&c1_touched};
 443     N14::C c2 = {&c2_touched};
 444     assert(std::strong_order(c1, c2) == std::strong_ordering::equal);
 445     assert(!c1_touched);
 446     assert(c2_touched);
 447
 448     return true;
 449 }
 450
 451 int main(int, char**)
 452 {
 453     test_1_1();
 454     test_1_2();
 455     test_1_3<float>();
 456     test_1_3<double>();
 457     // test_1_3<long double>();  // UNIMPLEMENTED
 458     test_1_4();
 459
 460     static_assert(test_1_3<float>());
 461     static_assert(test_1_3<double>());
 462     // static_assert(test_1_3<long double>());  // UNIMPLEMENTED
 463     static_assert(test_1_4());
 464
 465     return 0;
 466 }