libs/hana/test/_include/laws/monad_plus.hpp

   1 // Copyright Louis Dionne 2013-2017
   2 // Distributed under the Boost Software License, Version 1.0.
   3 // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   4
   5 #ifndef BOOST_HANA_TEST_LAWS_MONAD_PLUS_HPP
   6 #define BOOST_HANA_TEST_LAWS_MONAD_PLUS_HPP
   7
   8 #include <boost/hana/append.hpp>
   9 #include <boost/hana/assert.hpp>
  10 #include <boost/hana/bool.hpp>
  11 #include <boost/hana/chain.hpp>
  12 #include <boost/hana/concat.hpp>
  13 #include <boost/hana/concept/comparable.hpp>
  14 #include <boost/hana/concept/monad_plus.hpp>
  15 #include <boost/hana/concept/sequence.hpp>
  16 #include <boost/hana/core/make.hpp>
  17 #include <boost/hana/core/when.hpp>
  18 #include <boost/hana/cycle.hpp>
  19 #include <boost/hana/empty.hpp>
  20 #include <boost/hana/equal.hpp>
  21 #include <boost/hana/filter.hpp>
  22 #include <boost/hana/for_each.hpp>
  23 #include <boost/hana/functional/capture.hpp>
  24 #include <boost/hana/functional/compose.hpp>
  25 #include <boost/hana/integral_constant.hpp>
  26 #include <boost/hana/lift.hpp>
  27 #include <boost/hana/not.hpp>
  28 #include <boost/hana/not_equal.hpp>
  29 #include <boost/hana/prefix.hpp>
  30 #include <boost/hana/prepend.hpp>
  31 #include <boost/hana/remove.hpp>
  32 #include <boost/hana/remove_if.hpp>
  33 #include <boost/hana/replicate.hpp>
  34 #include <boost/hana/suffix.hpp>
  35
  36 #include <laws/base.hpp>
  37
  38
  39 namespace boost { namespace hana { namespace test {
  40     template <typename M, typename = when<true>>
  41     struct TestMonadPlus : TestMonadPlus<M, laws> {
  42         using TestMonadPlus<M, laws>::TestMonadPlus;
  43     };
  44
  45     template <typename M>
  46     struct TestMonadPlus<M, laws> {
  47         template <typename Xs, typename Predicates, typename Values>
  48         TestMonadPlus(Xs xs, Predicates predicates, Values values) {
  49             hana::for_each(xs, [](auto a) {
  50                 static_assert(MonadPlus<decltype(a)>{}, "");
  51
  52                 // left identity
  53                 BOOST_HANA_CHECK(hana::equal(
  54                     hana::concat(hana::empty<M>(), a),
  55                     a
  56                 ));
  57
  58                 // right identity
  59                 BOOST_HANA_CHECK(hana::equal(
  60                     hana::concat(a, hana::empty<M>()),
  61                     a
  62                 ));
  63
  64                 // absorption
  65                 auto f = hana::compose(lift<M>, test::_injection<0>{});
  66                 BOOST_HANA_CHECK(hana::equal(
  67                     hana::chain(hana::empty<M>(), f),
  68                     hana::empty<M>()
  69                 ));
  70
  71                 BOOST_HANA_CHECK(hana::equal(
  72                     hana::chain(a, hana::always(hana::empty<M>())),
  73                     hana::empty<M>()
  74                 ));
  75
  76             });
  77
  78             // associativity
  79             foreach3(xs, [](auto a, auto b, auto c) {
  80                 BOOST_HANA_CHECK(hana::equal(
  81                     hana::concat(a, hana::concat(b, c)),
  82                     hana::concat(hana::concat(a, b), c)
  83                 ));
  84             });
  85
  86             // Default method definitions
  87             hana::for_each(xs, hana::capture(predicates, values)(
  88             [](auto predicates, auto values, auto x) {
  89
  90                 // remove_if(x, pred) == filter(x, negated pred)
  91                 hana::for_each(predicates, hana::capture(x)([](auto x, auto pred) {
  92                     BOOST_HANA_CHECK(hana::equal(
  93                         hana::remove_if(x, pred),
  94                         hana::filter(x, hana::compose(hana::not_, pred))
  95                     ));
  96                 }));
  97
  98                 // remove(x, value) == remove_if(x, equal.to(value))
  99                 hana::for_each(values, hana::capture(x)([](auto x, auto value) {
 100                     BOOST_HANA_CHECK(hana::equal(
 101                         hana::remove(x, value),
 102                         hana::remove_if(x, hana::equal.to(value))
 103                     ));
 104                 }));
 105             }));
 106         }
 107     };
 108
 109     template <typename S>
 110     struct TestMonadPlus<S, when<Sequence<S>::value>>
 111         : TestMonadPlus<S, laws>
 112     {
 113         template <int i>
 114         using eq = test::ct_eq<i>;
 115
 116         struct undefined { };
 117
 118         template <typename Xs, typename Predicates, typename Values>
 119         TestMonadPlus(Xs xs, Predicates predicates, Values values)
 120             : TestMonadPlus<S, laws>{xs, predicates, values}
 121         {
 122             auto z = eq<999>{};
 123             constexpr auto list = make<S>;
 124
 125             //////////////////////////////////////////////////////////////////
 126             // empty
 127             //////////////////////////////////////////////////////////////////
 128             BOOST_HANA_CONSTANT_CHECK(equal(
 129                 hana::empty<S>(), list()
 130             ));
 131
 132             //////////////////////////////////////////////////////////////////
 133             // concat
 134             //////////////////////////////////////////////////////////////////
 135             BOOST_HANA_CONSTANT_CHECK(equal(
 136                 concat(list(), list()),
 137                 list()
 138             ));
 139             BOOST_HANA_CONSTANT_CHECK(equal(
 140                 concat(list(), list(eq<0>{})),
 141                 list(eq<0>{})
 142             ));
 143             BOOST_HANA_CONSTANT_CHECK(equal(
 144                 concat(list(), list(eq<0>{}, eq<1>{})),
 145                 list(eq<0>{}, eq<1>{})
 146             ));
 147
 148             BOOST_HANA_CONSTANT_CHECK(equal(
 149                 concat(list(eq<0>{}), list()),
 150                 list(eq<0>{})
 151             ));
 152             BOOST_HANA_CONSTANT_CHECK(equal(
 153                 concat(list(eq<0>{}), list(eq<1>{})),
 154                 list(eq<0>{}, eq<1>{})
 155             ));
 156             BOOST_HANA_CONSTANT_CHECK(equal(
 157                 concat(list(eq<0>{}), list(eq<1>{}, eq<2>{})),
 158                 list(eq<0>{}, eq<1>{}, eq<2>{})
 159             ));
 160
 161             BOOST_HANA_CONSTANT_CHECK(equal(
 162                 concat(list(eq<0>{}, eq<1>{}), list()),
 163                 list(eq<0>{}, eq<1>{})
 164             ));
 165             BOOST_HANA_CONSTANT_CHECK(equal(
 166                 concat(list(eq<0>{}, eq<1>{}), list(eq<2>{})),
 167                 list(eq<0>{}, eq<1>{}, eq<2>{})
 168             ));
 169             BOOST_HANA_CONSTANT_CHECK(equal(
 170                 concat(list(eq<0>{}, eq<1>{}), list(eq<2>{}, eq<3>{})),
 171                 list(eq<0>{}, eq<1>{}, eq<2>{}, eq<3>{})
 172             ));
 173
 174
 175             BOOST_HANA_CONSTANT_CHECK(equal(
 176                 concat(list(), list()),
 177                 list()
 178             ));
 179             BOOST_HANA_CONSTEXPR_CHECK(equal(
 180                 concat(list(1), list()),
 181                 list(1)
 182             ));
 183             BOOST_HANA_CONSTEXPR_CHECK(equal(
 184                 concat(list(), list(1)),
 185                 list(1)
 186             ));
 187             BOOST_HANA_CONSTEXPR_CHECK(equal(
 188                 concat(list(1), list('2')),
 189                 list(1, '2')
 190             ));
 191             BOOST_HANA_CONSTEXPR_CHECK(equal(
 192                 concat(list(1, '2'), list(3.3)),
 193                 list(1, '2', 3.3)
 194             ));
 195
 196
 197             //////////////////////////////////////////////////////////////////
 198             // filter
 199             //////////////////////////////////////////////////////////////////
 200             BOOST_HANA_CONSTANT_CHECK(equal(
 201                 filter(list(), undefined{}),
 202                 list()
 203             ));
 204
 205             BOOST_HANA_CONSTANT_CHECK(equal(
 206                 filter(list(z), not_equal.to(z)),
 207                 list()
 208             ));
 209             BOOST_HANA_CONSTANT_CHECK(equal(
 210                 filter(list(eq<1>{}), not_equal.to(z)),
 211                 list(eq<1>{})
 212             ));
 213
 214             BOOST_HANA_CONSTANT_CHECK(equal(
 215                 filter(list(eq<1>{}, eq<2>{}), not_equal.to(z)),
 216                 list(eq<1>{}, eq<2>{})
 217             ));
 218             BOOST_HANA_CONSTANT_CHECK(equal(
 219                 filter(list(z, eq<2>{}), not_equal.to(z)),
 220                 list(eq<2>{})
 221             ));
 222             BOOST_HANA_CONSTANT_CHECK(equal(
 223                 filter(list(eq<1>{}, z), not_equal.to(z)),
 224                 list(eq<1>{})
 225             ));
 226
 227             BOOST_HANA_CONSTANT_CHECK(equal(
 228                 filter(list(z, eq<2>{}, eq<3>{}), not_equal.to(z)),
 229                 list(eq<2>{}, eq<3>{})
 230             ));
 231             BOOST_HANA_CONSTANT_CHECK(equal(
 232                 filter(list(eq<1>{}, z, eq<3>{}), not_equal.to(z)),
 233                 list(eq<1>{}, eq<3>{})
 234             ));
 235             BOOST_HANA_CONSTANT_CHECK(equal(
 236                 filter(list(eq<1>{}, eq<2>{}, z), not_equal.to(z)),
 237                 list(eq<1>{}, eq<2>{})
 238             ));
 239             BOOST_HANA_CONSTANT_CHECK(equal(
 240                 filter(list(eq<1>{}, z, z), not_equal.to(z)),
 241                 list(eq<1>{})
 242             ));
 243             BOOST_HANA_CONSTANT_CHECK(equal(
 244                 filter(list(z, eq<2>{}, z), not_equal.to(z)),
 245                 list(eq<2>{})
 246             ));
 247             BOOST_HANA_CONSTANT_CHECK(equal(
 248                 filter(list(z, z, eq<3>{}), not_equal.to(z)),
 249                 list(eq<3>{})
 250             ));
 251
 252             BOOST_HANA_CONSTANT_CHECK(equal(
 253                 filter(list(eq<1>{}, eq<2>{}, eq<3>{}, eq<4>{}, z), not_equal.to(z)),
 254                 list(eq<1>{}, eq<2>{}, eq<3>{}, eq<4>{})
 255             ));
 256
 257             //////////////////////////////////////////////////////////////////
 258             // prepend
 259             //////////////////////////////////////////////////////////////////
 260             BOOST_HANA_CONSTANT_CHECK(equal(
 261                 prepend(list(), eq<0>{}),
 262                 list(eq<0>{})
 263             ));
 264             BOOST_HANA_CONSTANT_CHECK(equal(
 265                 prepend(list(eq<1>{}), eq<0>{}),
 266                 list(eq<0>{}, eq<1>{})
 267             ));
 268             BOOST_HANA_CONSTANT_CHECK(equal(
 269                 prepend(list(eq<1>{}, eq<2>{}), eq<0>{}),
 270                 list(eq<0>{}, eq<1>{}, eq<2>{})
 271             ));
 272             BOOST_HANA_CONSTANT_CHECK(equal(
 273                 prepend(list(eq<1>{}, eq<2>{}, eq<3>{}), eq<0>{}),
 274                 list(eq<0>{}, eq<1>{}, eq<2>{}, eq<3>{})
 275             ));
 276
 277
 278             BOOST_HANA_CONSTEXPR_CHECK(equal(
 279                 prepend(list(), 1),
 280                 list(1)
 281             ));
 282             BOOST_HANA_CONSTEXPR_CHECK(equal(
 283                 prepend(list('2'), 1),
 284                 list(1, '2')
 285             ));
 286             BOOST_HANA_CONSTEXPR_CHECK(equal(
 287                 prepend(list('2', 3.3), 1),
 288                 list(1, '2', 3.3)
 289             ));
 290
 291             //////////////////////////////////////////////////////////////////
 292             // append
 293             //////////////////////////////////////////////////////////////////
 294             BOOST_HANA_CONSTANT_CHECK(equal(
 295                 append(list(), eq<0>{}),
 296                 list(eq<0>{})
 297             ));
 298             BOOST_HANA_CONSTANT_CHECK(equal(
 299                 append(list(eq<0>{}), eq<1>{}),
 300                 list(eq<0>{}, eq<1>{})
 301             ));
 302             BOOST_HANA_CONSTANT_CHECK(equal(
 303                 append(list(eq<0>{}, eq<1>{}), eq<2>{}),
 304                 list(eq<0>{}, eq<1>{}, eq<2>{})
 305             ));
 306
 307             BOOST_HANA_CONSTEXPR_CHECK(equal(
 308                 append(list(), 1), list(1)
 309             ));
 310             BOOST_HANA_CONSTEXPR_CHECK(equal(
 311                 append(list(1), '2'), list(1, '2')
 312             ));
 313             BOOST_HANA_CONSTEXPR_CHECK(equal(
 314                 append(list(1, '2'), 3.3), list(1, '2', 3.3)
 315             ));
 316
 317
 318             //////////////////////////////////////////////////////////////////
 319             // cycle
 320             //////////////////////////////////////////////////////////////////
 321             BOOST_HANA_CONSTANT_CHECK(equal(
 322                 cycle(list(), size_c<0>),
 323                 list()
 324             ));
 325             BOOST_HANA_CONSTANT_CHECK(equal(
 326                 cycle(list(), size_c<1>),
 327                 list()
 328             ));
 329             BOOST_HANA_CONSTANT_CHECK(equal(
 330                 cycle(list(), size_c<2>),
 331                 list()
 332             ));
 333             BOOST_HANA_CONSTANT_CHECK(equal(
 334                 cycle(list(), size_c<3>),
 335                 list()
 336             ));
 337
 338
 339             BOOST_HANA_CONSTANT_CHECK(equal(
 340                 cycle(list(eq<0>{}), size_c<0>),
 341                 list()
 342             ));
 343             BOOST_HANA_CONSTANT_CHECK(equal(
 344                 cycle(list(eq<0>{}), size_c<1>),
 345                 list(eq<0>{})
 346             ));
 347             BOOST_HANA_CONSTANT_CHECK(equal(
 348                 cycle(list(eq<0>{}), size_c<2>),
 349                 list(eq<0>{}, eq<0>{})
 350             ));
 351             BOOST_HANA_CONSTANT_CHECK(equal(
 352                 cycle(list(eq<0>{}), size_c<3>),
 353                 list(eq<0>{}, eq<0>{}, eq<0>{})
 354             ));
 355
 356
 357             BOOST_HANA_CONSTANT_CHECK(equal(
 358                 cycle(list(eq<0>{}, eq<1>{}), size_c<0>),
 359                 list()
 360             ));
 361             BOOST_HANA_CONSTANT_CHECK(equal(
 362                 cycle(list(eq<0>{}, eq<1>{}), size_c<1>),
 363                 list(eq<0>{}, eq<1>{})
 364             ));
 365             BOOST_HANA_CONSTANT_CHECK(equal(
 366                 cycle(list(eq<0>{}, eq<1>{}), size_c<2>),
 367                 list(eq<0>{}, eq<1>{}, eq<0>{}, eq<1>{})
 368             ));
 369             BOOST_HANA_CONSTANT_CHECK(equal(
 370                 cycle(list(eq<0>{}, eq<1>{}), size_c<3>),
 371                 list(eq<0>{}, eq<1>{}, eq<0>{}, eq<1>{}, eq<0>{}, eq<1>{})
 372             ));
 373
 374
 375             BOOST_HANA_CONSTANT_CHECK(equal(
 376                 cycle(list(eq<0>{}, eq<1>{}, eq<2>{}), size_c<0>),
 377                 list()
 378             ));
 379             BOOST_HANA_CONSTANT_CHECK(equal(
 380                 cycle(list(eq<0>{}, eq<1>{}, eq<2>{}), size_c<1>),
 381                 list(eq<0>{}, eq<1>{}, eq<2>{})
 382             ));
 383             BOOST_HANA_CONSTANT_CHECK(equal(
 384                 cycle(list(eq<0>{}, eq<1>{}, eq<2>{}), size_c<2>),
 385                 list(eq<0>{}, eq<1>{}, eq<2>{}, eq<0>{}, eq<1>{}, eq<2>{})
 386             ));
 387             BOOST_HANA_CONSTANT_CHECK(equal(
 388                 cycle(list(eq<0>{}, eq<1>{}, eq<2>{}), size_c<3>),
 389                 list(eq<0>{}, eq<1>{}, eq<2>{}, eq<0>{}, eq<1>{}, eq<2>{}, eq<0>{}, eq<1>{}, eq<2>{})
 390             ));
 391
 392             //////////////////////////////////////////////////////////////////
 393             // remove_if
 394             //////////////////////////////////////////////////////////////////
 395             BOOST_HANA_CONSTANT_CHECK(equal(
 396                 remove_if(list(), undefined{}),
 397                 list()
 398             ));
 399
 400             BOOST_HANA_CONSTANT_CHECK(equal(
 401                 remove_if(list(eq<0>{}), equal.to(z)),
 402                 list(eq<0>{})
 403             ));
 404             BOOST_HANA_CONSTANT_CHECK(equal(
 405                 remove_if(list(z), equal.to(z)),
 406                 list()
 407             ));
 408
 409             BOOST_HANA_CONSTANT_CHECK(equal(
 410                 remove_if(list(eq<0>{}, eq<1>{}), equal.to(z)),
 411                 list(eq<0>{}, eq<1>{})
 412             ));
 413             BOOST_HANA_CONSTANT_CHECK(equal(
 414                 remove_if(list(z, eq<1>{}), equal.to(z)),
 415                 list(eq<1>{})
 416             ));
 417             BOOST_HANA_CONSTANT_CHECK(equal(
 418                 remove_if(list(eq<0>{}, z), equal.to(z)),
 419                 list(eq<0>{})
 420             ));
 421             BOOST_HANA_CONSTANT_CHECK(equal(
 422                 remove_if(list(z, z), equal.to(z)),
 423                 list()
 424             ));
 425
 426             BOOST_HANA_CONSTANT_CHECK(equal(
 427                 remove_if(list(eq<0>{}, eq<1>{}, eq<2>{}), equal.to(z)),
 428                 list(eq<0>{}, eq<1>{}, eq<2>{})
 429             ));
 430             BOOST_HANA_CONSTANT_CHECK(equal(
 431                 remove_if(list(eq<0>{}, eq<1>{}, z), equal.to(z)),
 432                 list(eq<0>{}, eq<1>{})
 433             ));
 434             BOOST_HANA_CONSTANT_CHECK(equal(
 435                 remove_if(list(eq<0>{}, z, eq<2>{}), equal.to(z)),
 436                 list(eq<0>{}, eq<2>{})
 437             ));
 438             BOOST_HANA_CONSTANT_CHECK(equal(
 439                 remove_if(list(z, eq<1>{}, eq<2>{}), equal.to(z)),
 440                 list(eq<1>{}, eq<2>{})
 441             ));
 442             BOOST_HANA_CONSTANT_CHECK(equal(
 443                 remove_if(list(z, z, eq<2>{}), equal.to(z)),
 444                 list(eq<2>{})
 445             ));
 446             BOOST_HANA_CONSTANT_CHECK(equal(
 447                 remove_if(list(eq<0>{}, z, z), equal.to(z)),
 448                 list(eq<0>{})
 449             ));
 450             BOOST_HANA_CONSTANT_CHECK(equal(
 451                 remove_if(list(z, z, z), equal.to(z)),
 452                 list()
 453             ));
 454
 455             //////////////////////////////////////////////////////////////////
 456             // remove
 457             //////////////////////////////////////////////////////////////////
 458             BOOST_HANA_CONSTANT_CHECK(equal(
 459                 hana::remove(list(), undefined{}),
 460                 list()
 461             ));
 462
 463             BOOST_HANA_CONSTANT_CHECK(equal(
 464                 hana::remove(list(eq<0>{}), z),
 465                 list(eq<0>{})
 466             ));
 467             BOOST_HANA_CONSTANT_CHECK(equal(
 468                 hana::remove(list(z), z),
 469                 list()
 470             ));
 471
 472             BOOST_HANA_CONSTANT_CHECK(equal(
 473                 hana::remove(list(eq<0>{}, eq<1>{}), z),
 474                 list(eq<0>{}, eq<1>{})
 475             ));
 476             BOOST_HANA_CONSTANT_CHECK(equal(
 477                 hana::remove(list(z, eq<1>{}), z),
 478                 list(eq<1>{})
 479             ));
 480             BOOST_HANA_CONSTANT_CHECK(equal(
 481                 hana::remove(list(eq<0>{}, z), z),
 482                 list(eq<0>{})
 483             ));
 484             BOOST_HANA_CONSTANT_CHECK(equal(
 485                 hana::remove(list(z, z), z),
 486                 list()
 487             ));
 488
 489             BOOST_HANA_CONSTANT_CHECK(equal(
 490                 hana::remove(list(eq<0>{}, eq<1>{}, eq<2>{}), z),
 491                 list(eq<0>{}, eq<1>{}, eq<2>{})
 492             ));
 493             BOOST_HANA_CONSTANT_CHECK(equal(
 494                 hana::remove(list(eq<0>{}, eq<1>{}, z), z),
 495                 list(eq<0>{}, eq<1>{})
 496             ));
 497             BOOST_HANA_CONSTANT_CHECK(equal(
 498                 hana::remove(list(eq<0>{}, z, eq<2>{}), z),
 499                 list(eq<0>{}, eq<2>{})
 500             ));
 501             BOOST_HANA_CONSTANT_CHECK(equal(
 502                 hana::remove(list(z, eq<1>{}, eq<2>{}), z),
 503                 list(eq<1>{}, eq<2>{})
 504             ));
 505             BOOST_HANA_CONSTANT_CHECK(equal(
 506                 hana::remove(list(z, z, eq<2>{}), z),
 507                 list(eq<2>{})
 508             ));
 509             BOOST_HANA_CONSTANT_CHECK(equal(
 510                 hana::remove(list(eq<0>{}, z, z), z),
 511                 list(eq<0>{})
 512             ));
 513             BOOST_HANA_CONSTANT_CHECK(equal(
 514                 hana::remove(list(z, z, z), z),
 515                 list()
 516             ));
 517
 518             //////////////////////////////////////////////////////////////////
 519             // replicate
 520             //////////////////////////////////////////////////////////////////
 521             BOOST_HANA_CONSTANT_CHECK(equal(
 522                 replicate<S>(eq<0>{}, size_c<0>),
 523                 list()
 524             ));
 525
 526             BOOST_HANA_CONSTANT_CHECK(equal(
 527                 replicate<S>(eq<0>{}, size_c<1>),
 528                 list(eq<0>{})
 529             ));
 530
 531             BOOST_HANA_CONSTANT_CHECK(equal(
 532                 replicate<S>(eq<0>{}, size_c<2>),
 533                 list(eq<0>{}, eq<0>{})
 534             ));
 535
 536             BOOST_HANA_CONSTANT_CHECK(equal(
 537                 replicate<S>(eq<0>{}, size_c<3>),
 538                 list(eq<0>{}, eq<0>{}, eq<0>{})
 539             ));
 540
 541             BOOST_HANA_CONSTANT_CHECK(equal(
 542                 replicate<S>(eq<0>{}, size_c<4>),
 543                 list(eq<0>{}, eq<0>{}, eq<0>{}, eq<0>{})
 544             ));
 545
 546             BOOST_HANA_CONSTANT_CHECK(equal(
 547                 replicate<S>(eq<0>{}, size_c<5>),
 548                 list(eq<0>{}, eq<0>{}, eq<0>{}, eq<0>{}, eq<0>{})
 549             ));
 550
 551
 552             //////////////////////////////////////////////////////////////////
 553             // prefix
 554             //////////////////////////////////////////////////////////////////
 555             BOOST_HANA_CONSTANT_CHECK(equal(
 556                 prefix(list(), z),
 557                 list()
 558             ));
 559
 560             BOOST_HANA_CONSTANT_CHECK(equal(
 561                 prefix(list(eq<0>{}), z),
 562                 list(z, eq<0>{})
 563             ));
 564
 565             BOOST_HANA_CONSTANT_CHECK(equal(
 566                 prefix(list(eq<0>{}, eq<1>{}), z),
 567                 list(z, eq<0>{}, z, eq<1>{})
 568             ));
 569
 570             BOOST_HANA_CONSTANT_CHECK(equal(
 571                 prefix(list(eq<0>{}, eq<1>{}, eq<2>{}), z),
 572                 list(z, eq<0>{}, z, eq<1>{}, z, eq<2>{})
 573             ));
 574
 575             BOOST_HANA_CONSTANT_CHECK(equal(
 576                 prefix(list(eq<0>{}, eq<1>{}, eq<2>{}, eq<3>{}), z),
 577                 list(z, eq<0>{}, z, eq<1>{}, z, eq<2>{}, z, eq<3>{})
 578             ));
 579
 580
 581             //////////////////////////////////////////////////////////////////
 582             // suffix
 583             //////////////////////////////////////////////////////////////////
 584             BOOST_HANA_CONSTANT_CHECK(equal(
 585                 suffix(list(), z),
 586                 list()
 587             ));
 588
 589             BOOST_HANA_CONSTANT_CHECK(equal(
 590                 suffix(list(eq<0>{}), z),
 591                 list(eq<0>{}, z)
 592             ));
 593
 594             BOOST_HANA_CONSTANT_CHECK(equal(
 595                 suffix(list(eq<0>{}, eq<1>{}), z),
 596                 list(eq<0>{}, z, eq<1>{}, z)
 597             ));
 598
 599             BOOST_HANA_CONSTANT_CHECK(equal(
 600                 suffix(list(eq<0>{}, eq<1>{}, eq<2>{}), z),
 601                 list(eq<0>{}, z, eq<1>{}, z, eq<2>{}, z)
 602             ));
 603
 604             BOOST_HANA_CONSTANT_CHECK(equal(
 605                 suffix(list(eq<0>{}, eq<1>{}, eq<2>{}, eq<3>{}), z),
 606                 list(eq<0>{}, z, eq<1>{}, z, eq<2>{}, z, eq<3>{}, z)
 607             ));
 608         }
 609     };
 610 }}} // end namespace boost::hana::test
 611
 612 #endif // !BOOST_HANA_TEST_LAWS_MONAD_PLUS_HPP