Hide keyboard shortcuts

Hot-keys on this page

r m x p   toggle line displays

j k   next/prev highlighted chunk

0   (zero) top of page

1   (one) first highlighted chunk

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

296

297

298

299

300

301

302

303

304

305

306

307

308

309

310

311

312

313

314

315

316

317

318

319

320

321

322

323

324

325

326

327

328

329

330

331

332

333

334

335

336

337

338

339

340

341

342

343

344

345

346

347

348

349

350

351

352

353

354

355

356

357

358

359

360

361

362

363

364

365

366

367

368

369

370

371

372

373

374

375

376

377

378

379

380

381

382

383

384

385

386

387

388

389

390

391

392

393

394

395

396

397

398

399

400

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

419

420

421

422

423

424

425

426

427

428

429

430

431

432

433

434

435

436

437

438

439

440

441

442

443

444

445

446

447

448

449

450

451

452

453

454

455

456

457

458

459

460

461

462

463

464

465

466

467

468

469

470

471

472

473

474

475

476

477

478

479

480

481

482

483

484

485

486

487

488

489

490

491

492

493

494

495

496

497

498

499

500

501

502

503

504

505

506

507

508

509

510

511

512

513

514

515

516

517

518

519

520

521

522

523

524

525

526

527

528

529

530

531

532

533

534

535

536

537

538

539

540

541

542

543

544

545

546

547

548

549

550

551

552

553

554

555

556

557

558

559

560

561

562

563

564

565

566

567

568

569

570

571

572

573

574

575

576

577

578

579

580

581

582

583

584

585

586

587

588

589

590

591

592

593

594

595

596

597

598

599

600

601

602

603

604

605

606

607

608

609

610

611

612

613

614

615

616

617

618

619

620

621

622

623

624

625

626

627

628

629

630

631

632

633

634

635

636

637

638

639

640

641

642

643

644

645

646

647

648

649

650

651

652

653

654

655

656

657

658

659

660

661

662

663

664

665

666

667

668

669

670

671

672

673

674

675

676

677

678

679

680

681

682

683

684

685

686

687

688

689

690

691

692

693

694

695

696

697

698

699

700

701

702

703

704

705

706

707

708

709

710

711

712

713

714

715

716

717

718

719

720

721

722

723

724

725

726

727

728

729

730

731

732

733

734

735

736

737

738

739

740

741

742

743

744

745

746

747

748

749

750

751

752

753

754

755

756

757

758

759

760

761

762

763

764

765

766

767

768

769

770

771

772

773

774

775

776

777

778

779

780

781

782

783

784

785

786

787

788

789

790

791

792

793

794

795

796

797

798

799

800

801

802

803

804

805

806

807

808

809

810

811

812

813

814

815

816

817

818

819

820

821

822

823

824

825

826

827

828

829

830

831

832

833

834

835

836

837

838

839

840

841

842

843

844

845

846

847

848

849

850

851

852

853

854

855

856

857

858

859

860

861

862

863

864

865

866

867

868

869

870

871

872

873

874

875

876

877

878

879

880

881

882

883

884

885

886

887

888

889

890

891

892

893

894

895

896

897

898

899

900

901

902

903

904

905

906

907

908

909

910

911

912

913

914

915

916

917

918

919

920

921

922

923

924

925

926

927

928

929

930

931

932

933

934

935

936

937

938

939

940

941

942

943

944

945

946

947

948

949

950

951

952

953

954

955

956

957

958

959

960

961

962

963

964

965

966

967

968

969

970

971

972

973

974

975

976

977

978

979

980

981

982

983

984

985

986

987

988

989

990

991

992

993

994

995

996

997

998

999

1000

1001

1002

1003

1004

1005

1006

1007

1008

1009

1010

1011

1012

1013

1014

1015

1016

1017

1018

1019

1020

1021

1022

1023

1024

1025

1026

1027

1028

1029

1030

1031

1032

1033

1034

1035

1036

1037

1038

1039

1040

1041

1042

1043

1044

1045

1046

1047

r""" 

Operation Tables 

 

This module implements general operation tables, which are very matrix-like. 

""" 

 

#***************************************************************************** 

# Copyright (C) 2010 Rob Beezer <beezer at ups.edu> 

# 

# This program is free software: you can redistribute it and/or modify 

# it under the terms of the GNU General Public License as published by 

# the Free Software Foundation, either version 2 of the License, or 

# (at your option) any later version. 

# http://www.gnu.org/licenses/ 

#***************************************************************************** 

 

from __future__ import absolute_import 

 

import six 

from sage.structure.sage_object import SageObject 

 

class OperationTable(SageObject): 

r""" 

An object that represents a binary operation as a table. 

 

Primarily this object is used to provide a 

:meth:`~sage.categories.magmas.Magmas.ParentMethods.multiplication_table` 

for objects in the category of magmas (monoids, groups, ...) and 

:meth:`~sage.categories.additive_magmas.AdditiveMagmas.ParentMethods.addition_table` 

for objects in the category of commutative additive magmas 

(additive monoids, groups, ...). 

 

INPUT: 

 

- ``S`` - a finite algebraic structure (or finite iterable) 

 

- ``operation`` - a function of two variables that accepts pairs 

of elements from ``S``. A natural source of such functions is 

the Python :mod:`operator` module, and in particular 

:func:`operator.add` and :func:`operator.mul`. This may also 

be a function defined with ``lambda`` or ``def.`` 

 

- ``names`` - (default: ``'letters'``) The type of names 

used, values are: 

 

* ``'letters'`` - lowercase ASCII letters are used 

for a base 26 representation of the elements' 

positions in the list given by 

:meth:`~sage.matrix.operation_table.OperationTable.column_keys`, 

padded to a common width with leading 'a's. 

* ``'digits'`` - base 10 representation of the 

elements' positions in the list given by 

:meth:`~sage.matrix.operation_table.OperationTable.column_keys`, 

padded to a common width with leading zeros. 

* ``'elements'`` - the string representations 

of the elements themselves. 

* a list - a list of strings, where the length 

of the list equals the number of elements. 

 

- ``elements`` - (default: ``None``) A list of elements of ``S``, 

in forms that can be coerced into the structure, eg. their 

string representations. This may be used to impose an alternate 

ordering on the elements of `S``, perhaps when this is used in 

the context of a particular structure. The default is to use 

whatever ordering the ``S.list()`` method returns. `elements`` 

can also be a subset which is closed under the operation, useful 

perhaps when the set is infinite. 

 

OUTPUT: 

An object with methods that abstracts multiplication tables, 

addition tables, Cayley tables, etc. It should be general 

enough to be useful for any finite algebraic structure 

whose elements can be combined with a binary operation. 

This is not necessarily meant be constructed directly, but instead 

should be useful for constructing operation tables of various 

algebraic structures that have binary operations. 

 

EXAMPLES: 

 

In its most basic use, the table needs a structure and an operation:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=SymmetricGroup(3) 

sage: OperationTable(G, operation = operator.mul) 

* a b c d e f 

+------------ 

a| a b c d e f 

b| b a f e d c 

c| c e d a f b 

d| d f a c b e 

e| e c b f a d 

f| f d e b c a 

 

With two operations present, we can specify which operation we 

want:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: R=Integers(6) 

sage: OperationTable(R, operation=operator.add) 

+ a b c d e f 

+------------ 

a| a b c d e f 

b| b c d e f a 

c| c d e f a b 

d| d e f a b c 

e| e f a b c d 

f| f a b c d e 

 

The default symbol set for elements is lowercase ASCII letters, 

which take on a base 26 flavor for structures with more than 

26 elements. :: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=DihedralGroup(14) 

sage: OperationTable(G, operator.mul, names='letters') 

* aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw ax ay az ba bb 

+------------------------------------------------------------------------------------ 

aa| aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw ax ay az ba bb 

ab| ab aa ae ah ac aj ak ad am af ag ar ai ap at an av al aw ao az aq as ba bb au ax ay 

ac| ac ad af ai ab ag al aa an ae aj aq ah ao au am as ak ax ap ay ar av bb ba at aw az 

ad| ad ac ab aa af ae aj ai ah ag al ak an am ap ao ar aq av au at as ax aw az ay bb ba 

ae| ae ah aj am aa ak ar ab ap ac af av ad at az ai aw ag ba an bb al aq ay ax ao as au 

af| af ai ag an ad al aq ac ao ab ae as aa au ay ah ax aj bb am ba ak ar az aw ap av at 

ag| ag an al ao ai aq as af au ad ab ax ac ay ba aa bb ae az ah aw aj ak at av am ar ap 

ah| ah ae aa ab aj ac af am ad ak ar ag ap ai an at al av aq az ao aw ba as au bb ay ax 

ai| ai af ad ac ag ab ae an aa al aq aj ao ah am au ak as ar ay ap ax bb av at ba az aw 

aj| aj am ak ap ah ar av ae at aa ac aw ab az bb ad ba af ay ai ax ag al au as an aq ao 

ak| ak ap ar at am av aw aj az ah aa ba ae bb ax ab ay ac au ad as af ag ao aq ai al an 

al| al ao aq au an as ax ag ay ai ad bb af ba aw ac az ab at aa av ae aj ap ar ah ak am 

am| am aj ah ae ak aa ac ap ab ar av af at ad ai az ag aw al bb an ba ay aq ao ax au as 

an| an ag ai af al ad ab ao ac aq as ae au aa ah ay aj ax ak ba am bb az ar ap aw at av 

ao| ao al an ag aq ai ad au af as ax ab ay ac aa ba ae bb aj aw ah az at ak am av ap ar 

ap| ap ak am aj ar ah aa at ae av aw ac az ab ad bb af ba ag ax ai ay au al an as ao aq 

aq| aq au as ay ao ax bb al ba an ai az ag aw av af at ad ap ac ar ab ae am ak aa aj ah 

ar| ar at av az ap aw ba ak bb am ah ay aj ax as ae au aa ao ab aq ac af an al ad ag ai 

as| as ay ax ba au bb az aq aw ao an at al av ar ag ap ai am af ak ad ab ah aj ac ae aa 

at| at ar ap ak av am ah az aj aw ba aa bb ae ab ax ac ay af as ad au ao ag ai aq an al 

au| au aq ao al as an ai ay ag ax bb ad ba af ac aw ab az ae av aa at ap aj ah ar am ak 

av| av az aw bb at ba ay ar ax ap am au ak as aq aj ao ah an ae al aa ac ai ag ab af ad 

aw| aw bb ba ax az ay au av as at ap ao ar aq al ak an am ai aj ag ah aa ad af ae ac ab 

ax| ax ba bb aw ay az at as av au ao ap aq ar ak al am an ah ag aj ai ad aa ae af ab ac 

ay| ay as au aq ax ao an ba al bb az ai aw ag af av ad at ab ar ac ap am ae aa ak ah aj 

az| az av at ar aw ap am bb ak ba ay ah ax aj ae as aa au ac aq ab ao an af ad al ai ag 

ba| ba ax ay as bb au ao aw aq az at an av al ag ar ai ap ad ak af am ah ab ac aj aa ae 

bb| bb aw az av ba at ap ax ar ay au am as ak aj aq ah ao aa al ae an ai ac ab ag ad af 

 

Another symbol set is base 10 digits, padded with leading 

zeros to make a common width. :: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=AlternatingGroup(4) 

sage: OperationTable(G, operator.mul, names='digits') 

* 00 01 02 03 04 05 06 07 08 09 10 11 

+------------------------------------ 

00| 00 01 02 03 04 05 06 07 08 09 10 11 

01| 01 05 03 07 06 00 08 02 04 10 11 09 

02| 02 04 06 05 10 09 00 11 07 03 01 08 

03| 03 06 08 00 11 10 01 09 02 07 05 04 

04| 04 09 05 11 00 02 07 06 10 01 08 03 

05| 05 00 07 02 08 01 04 03 06 11 09 10 

06| 06 10 00 09 01 03 02 08 11 05 04 07 

07| 07 08 04 01 09 11 05 10 03 02 00 06 

08| 08 11 01 10 05 07 03 04 09 00 06 02 

09| 09 02 11 06 07 04 10 05 00 08 03 01 

10| 10 03 09 08 02 06 11 00 01 04 07 05 

11| 11 07 10 04 03 08 09 01 05 06 02 00 

 

If the group's elements are not too cumbersome, 

or the group is small, then the string representation 

of the elements can be used. :: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=AlternatingGroup(3) 

sage: OperationTable(G, operator.mul, names='elements') 

* () (1,2,3) (1,3,2) 

+------------------------ 

()| () (1,2,3) (1,3,2) 

(1,2,3)| (1,2,3) (1,3,2) () 

(1,3,2)| (1,3,2) () (1,2,3) 

 

You can give the elements any names you like, but they need to be ordered 

in the same order as returned by the 

:meth:`~sage.matrix.operation_table.OperationTable.column_keys` 

method. :: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=QuaternionGroup() 

sage: T=OperationTable(G, operator.mul) 

sage: T.column_keys() 

((), (1,2,3,4)(5,6,7,8), ..., (1,7,3,5)(2,6,4,8)) 

sage: names=['1', 'I', 'J', '-1', '-K', 'K', '-I', '-J'] 

sage: T.change_names(names=names) 

sage: sorted(T.translation().items()) 

[('-1', (1,3)(2,4)(5,7)(6,8)),..., ('K', (1,8,3,6)(2,7,4,5))] 

sage: T 

* 1 I J -1 -K K -I -J 

+------------------------ 

1| 1 I J -1 -K K -I -J 

I| I -1 K -I J -J 1 -K 

J| J -K -1 -J -I I K 1 

-1| -1 -I -J 1 K -K I J 

-K| -K -J I K -1 1 J -I 

K| K J -I -K 1 -1 -J I 

-I| -I 1 -K I -J J -1 K 

-J| -J K 1 J I -I -K -1 

 

With the right functions and a list comprehension, custom 

names can be easier. A multiplication table for hex digits 

(without carries):: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: R=Integers(16) 

sage: names=[hex(Integer(a)) for a in R] 

sage: OperationTable(R, operation=operator.mul, names=names) 

* 0 1 2 3 4 5 6 7 8 9 a b c d e f 

+-------------------------------- 

0| 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

1| 0 1 2 3 4 5 6 7 8 9 a b c d e f 

2| 0 2 4 6 8 a c e 0 2 4 6 8 a c e 

3| 0 3 6 9 c f 2 5 8 b e 1 4 7 a d 

4| 0 4 8 c 0 4 8 c 0 4 8 c 0 4 8 c 

5| 0 5 a f 4 9 e 3 8 d 2 7 c 1 6 b 

6| 0 6 c 2 8 e 4 a 0 6 c 2 8 e 4 a 

7| 0 7 e 5 c 3 a 1 8 f 6 d 4 b 2 9 

8| 0 8 0 8 0 8 0 8 0 8 0 8 0 8 0 8 

9| 0 9 2 b 4 d 6 f 8 1 a 3 c 5 e 7 

a| 0 a 4 e 8 2 c 6 0 a 4 e 8 2 c 6 

b| 0 b 6 1 c 7 2 d 8 3 e 9 4 f a 5 

c| 0 c 8 4 0 c 8 4 0 c 8 4 0 c 8 4 

d| 0 d a 7 4 1 e b 8 5 2 f c 9 6 3 

e| 0 e c a 8 6 4 2 0 e c a 8 6 4 2 

f| 0 f e d c b a 9 8 7 6 5 4 3 2 1 

 

This should be flexible enough to create a variety 

of such tables. :: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: from operator import xor 

sage: T=OperationTable(ZZ, xor, elements=range(8)) 

sage: T 

. a b c d e f g h 

+---------------- 

a| a b c d e f g h 

b| b a d c f e h g 

c| c d a b g h e f 

d| d c b a h g f e 

e| e f g h a b c d 

f| f e h g b a d c 

g| g h e f c d a b 

h| h g f e d c b a 

sage: names=['000', '001','010','011','100','101','110','111'] 

sage: T.change_names(names) 

sage: T.set_print_symbols('^', '\\land') 

sage: T 

^ 000 001 010 011 100 101 110 111 

+-------------------------------- 

000| 000 001 010 011 100 101 110 111 

001| 001 000 011 010 101 100 111 110 

010| 010 011 000 001 110 111 100 101 

011| 011 010 001 000 111 110 101 100 

100| 100 101 110 111 000 001 010 011 

101| 101 100 111 110 001 000 011 010 

110| 110 111 100 101 010 011 000 001 

111| 111 110 101 100 011 010 001 000 

 

sage: T = OperationTable([False, True], operator.or_, names = 'elements') 

sage: T 

. False True 

+------------ 

False| False True 

True| True True 

 

 

TESTS: 

 

Empty structures behave acceptably, though the ASCII table looks a bit 

odd. The LaTeX version works much better. :: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: L=FiniteSemigroups().example(()) 

sage: L 

An example of a finite semigroup: the left regular band generated by () 

sage: T=OperationTable(L, operation=operator.mul) 

sage: T 

* 

+ 

sage: T._latex_() 

'{\\setlength{\\arraycolsep}{2ex}\n\\begin{array}{r|*{0}{r}}\n\\multicolumn{1}{c|}{\\ast}\\\\\\hline\n\\end{array}}' 

 

If the algebraic structure cannot be listed (like when it is infinite) 

then there is no way to create a table. :: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: OperationTable(ZZ, operator.mul) 

Traceback (most recent call last): 

... 

ValueError: Integer Ring is infinite 

 

The value of ``elements`` must be a subset of the algebraic 

structure, in forms that can be coerced into the structure. 

Here we demonstrate the proper use first:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: H=CyclicPermutationGroup(4) 

sage: H.list() 

[(), (1,2,3,4), (1,3)(2,4), (1,4,3,2)] 

sage: elts = ['()', '(1,3)(2,4)'] 

sage: OperationTable(H, operator.mul, elements=elts) 

* a b 

+---- 

a| a b 

b| b a 

 

This can be rewritten so as to pass the actual elements of the 

group ``H``, using a simple ``for`` loop:: 

 

sage: L = H.list() #list of elements of the group H 

sage: elts = [L[i] for i in {0, 2}] 

sage: elts 

[(), (1,3)(2,4)] 

sage: OperationTable(H, operator.mul, elements=elts) 

* a b 

+---- 

a| a b 

b| b a 

 

Here are a couple of improper uses :: 

 

sage: elts.append(5) 

sage: OperationTable(H, operator.mul, elements=elts) 

Traceback (most recent call last): 

... 

TypeError: unable to coerce 5 into Cyclic group of order 4 as a permutation group 

sage: elts[2]='(1,3,2,4)' 

sage: OperationTable(H, operator.mul, elements=elts) 

Traceback (most recent call last): 

... 

TypeError: unable to coerce (1,3,2,4) into Cyclic group of order 4 as a permutation group 

sage: elts[2]='(1,2,3,4)' 

sage: OperationTable(H, operator.mul, elements=elts) 

Traceback (most recent call last): 

... 

ValueError: (1,3)(2,4)*(1,2,3,4)=(1,4,3,2), and so the set is not closed 

 

Unusable functions should be recognized as such:: 

 

sage: H=CyclicPermutationGroup(4) 

sage: OperationTable(H, operator.add) 

Traceback (most recent call last): 

... 

TypeError: elements () and () of Cyclic group of order 4 as a permutation group are incompatible with operation: <built-in function add> 

sage: from operator import xor 

sage: OperationTable(H, xor) 

Traceback (most recent call last): 

... 

TypeError: elements () and () of Cyclic group of order 4 as a permutation group are incompatible with operation: <built-in function xor> 

 

.. TODO:: 

 

Provide color and grayscale graphical representations of tables. 

See commented-out stubs in source code. 

 

AUTHOR: 

 

- Rob Beezer (2010-03-15) 

""" 

def __init__(self, S, operation, names='letters', elements=None): 

r""" 

TESTS:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=SymmetricGroup(3) 

sage: T=OperationTable(G, operator.mul) 

sage: TestSuite(T).run() 

""" 

# Determine the elements of S, specified or not 

# If elements are given, we check if they are all in S 

# Note: there exist listable infinite objects (like ZZ) 

if (elements is None): 

if hasattr(S, 'is_finite'): 

if not(S.is_finite()): 

raise ValueError('%s is infinite' % S) 

try: 

elems = tuple(S) 

except Exception: 

raise ValueError('unable to determine elements of %s' % S) 

else: 

elems = [] 

try: 

for e in elements: 

coerced = S(e) 

if not(coerced in elems): 

elems.append(coerced) 

except Exception: 

raise TypeError('unable to coerce %s into %s' % (e, S)) 

self._elts = elems 

self._n = len(self._elts) 

self._name_dict = {} 

 

# Map elements to strings 

self._width, self._names, self._name_dict = self._name_maker(names) 

 

# Determine the operation, if given by a string 

# Some simple symbols are supported, 

# Add support for other symbols in the supported dictionary 

# Triple is (function, ascii-symbol, latex-symbol) 

# ascii-symbol must be exactly one character wide 

# Note double-backslash to escape properly for latex 

from operator import add, mul 

supported = { 

add: (add, '+', '+'), 

mul: (mul, '*', '\\ast') 

} 

# default symbols for upper-left-hand-corner of table 

self._ascii_symbol = '.' 

self._latex_symbol = '\\cdot' 

if operation in supported.keys(): 

chosen = supported[operation] 

operation = chosen[0] 

self._ascii_symbol = chosen[1] 

self._latex_symbol = chosen[2] 

self._operation = operation 

# We assume now that operation is a function that acts 

# as a closed binary operation on the elements. 

# If not, we'll discover that next in actual use. 

 

self._table = [] 

 

# the elements might not be hashable. But if they are it is much 

# faster to lookup in a hash table rather than in a list! 

try: 

get_row = {e: i for i,e in enumerate(self._elts)}.__getitem__ 

except TypeError: 

get_row = self._elts.index 

 

for g in self._elts: 

row = [] 

for h in self._elts: 

try: 

result = self._operation(g, h) 

except Exception: 

raise TypeError('elements %s and %s of %s are incompatible with operation: %s' % (g,h,S,self._operation)) 

 

try: 

r = get_row(result) 

except (KeyError,ValueError): 

raise ValueError('%s%s%s=%s, and so the set is not closed' % (g, self._ascii_symbol, h, result)) 

 

row.append(r) 

self._table.append(row) 

 

def _name_maker(self, names): 

r""" 

Helper function to create names of elements of algebraic structures. 

 

INPUT: 

Identical to the input for :class:`OperationTable` and :meth:`change_names`, 

so look there for details. 

 

OUTPUT: 

 

- ``width`` - an integer giving the maximum width of the strings 

describing the elements. This is used for formatting the ASCII 

version of the table. 

- ``name_list`` - a list of strings naming the elements, in the 

same order as given by the :meth:`list` method. 

- ``name_dict`` - a dictionary giving the correspondence between the 

strings and the actual elements. So the keys are the strings and 

the values are the elements of the structure. 

 

EXAMPLES: 

 

This routine is tested extensively in the :class:`OperationTable` 

and :meth:`change_names` methods. So we just demonstrate 

the nature of the output here. :: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=SymmetricGroup(3) 

sage: T=OperationTable(G, operator.mul) 

sage: w, l, d = T._name_maker('letters') 

sage: w 

1 

sage: l[0] 

'a' 

sage: d['a'] 

() 

 

TESTS: 

 

We test the error conditions here, rather than as part of the 

doctests for the :class:`OperationTable` and :meth:`change_names` 

methods that rely on this one. :: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=AlternatingGroup(3) 

sage: T=OperationTable(G, operator.mul) 

sage: T._name_maker(['x']) 

Traceback (most recent call last): 

... 

ValueError: list of element names must be the same size as the set, 1 != 3 

sage: T._name_maker(['x', 'y', 4]) 

Traceback (most recent call last): 

... 

ValueError: list of element names must only contain strings, not 4 

sage: T._name_maker('blatzo') 

Traceback (most recent call last): 

... 

ValueError: element names must be a list, or one of the keywords: 'letters', 'digits', 'elements' 

""" 

from sage.functions.log import log 

name_list=[] 

if names == 'digits': 

if self._n == 0 or self._n == 1: 

width = 1 

else: 

width = int(log(self._n-1,10))+1 

for i in range(self._n): 

name_list.append('{0:0{1}d}'.format(i,width)) 

elif names == 'letters': 

from string import ascii_lowercase as letters 

from sage.rings.integer import Integer 

base = len(letters) 

if self._n == 0 or self._n == 1: 

width = 1 

else: 

width = int(log(self._n-1,base))+1 

for i in range(self._n): 

places = Integer(i).digits(base=base, digits=letters, padto=width) 

places.reverse() 

name_list.append(''.join(places)) 

elif names == 'elements': 

width = 0 

for e in self._elts: 

estr = repr(e) 

if len(estr) > width: 

width = len(estr) 

name_list.append(estr) 

elif isinstance(names, list): 

if len(names) != self._n: 

raise ValueError('list of element names must be the same size as the set, %s != %s'%(len(names), self._n)) 

width = 0 

for str in names: 

if not isinstance(str, six.string_types): 

raise ValueError('list of element names must only contain strings, not %s'%str) 

if len(str) > width: 

width = len(str) 

name_list.append(str) 

else: 

raise ValueError("element names must be a list, or one of the keywords: 'letters', 'digits', 'elements'") 

name_dict = {} 

for i in range(self._n): 

name_dict[name_list[i]]=self._elts[i] 

return width, name_list, name_dict 

 

def __getitem__(self, pair): 

r""" 

Returns the element of the table, given the elements indexing its position. 

 

INPUT: 

- pair -- two elements of the structure 

 

OUTPUT: 

The element of the structure computed by the operation for 

the two input elements (in the order provided). 

 

This uses the table as a look-up device. If you want to use 

the operation, then use the operation. 

 

EXAMPLES:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=DiCyclicGroup(3) 

sage: T=OperationTable(G, operator.mul) 

sage: T.column_keys() 

((), (1,3,2,4)(5,7), ..., (1,2)(3,4)(5,7,6)) 

sage: T[G('(1,2)(3,4)(5,6,7)'), G('(1,3,2,4)(5,7)')] 

(1,4,2,3)(5,6) 

 

TESTS:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G = DiCyclicGroup(3) 

sage: T = OperationTable(G, operator.mul) 

sage: T[G('(1,2)(3,4)(5,6,7)')] 

Traceback (most recent call last): 

... 

TypeError: indexing into an operation table requires exactly two elements 

sage: T[G('(1,2)(3,4)(5,6,7)'), G('(1,3,2,4)(5,7)'), G('(1,3,2,4)(5,7)')] 

Traceback (most recent call last): 

... 

TypeError: indexing into an operation table requires exactly two elements 

sage: T[2, 3] 

Traceback (most recent call last): 

... 

IndexError: invalid indices of operation table: (2, 3) 

sage: T['(1,512)', '(1,3,2,4)(5,7)'] 

Traceback (most recent call last): 

... 

IndexError: invalid indices of operation table: ((1,512), (1,3,2,4)(5,7)) 

""" 

if not (isinstance(pair, tuple) and len(pair) == 2): 

raise TypeError('indexing into an operation table requires exactly two elements') 

g, h = pair 

try: 

row = self._elts.index(g) 

col = self._elts.index(h) 

except ValueError: 

raise IndexError('invalid indices of operation table: (%s, %s)' % (g, h)) 

return self._elts[self._table[row][col]] 

 

def __eq__(self, other): 

r""" 

Returns the comparison between two tables. 

 

INPUT: 

 

- ``other`` - a second table to compare to ``self``. 

 

OUTPUT: 

Tables are equal if they have the same operation and elements. 

 

EXAMPLES:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=CyclicPermutationGroup(6) 

sage: H=CyclicPermutationGroup(3) 

sage: P=OperationTable(G, operator.mul) 

sage: Q=OperationTable(G, operator.mul) 

sage: R=OperationTable(H, operator.mul) 

sage: S=OperationTable(G, operator.truediv) 

sage: P == P, P == Q, P == R, P == S 

(True, True, False, False) 

""" 

return (self._elts == other._elts) and (self._operation == other._operation) 

 

def __ne__(self, other): 

""" 

Inequality test, by negation of :meth:`.__eq__`. 

 

EXAMPLES:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=CyclicPermutationGroup(6) 

sage: H=CyclicPermutationGroup(3) 

sage: P=OperationTable(G, operator.mul) 

sage: Q=OperationTable(G, operator.mul) 

sage: R=OperationTable(H, operator.mul) 

sage: S=OperationTable(G, operator.truediv) 

sage: P != P, P != Q, P != R, P != S 

(False, False, True, True) 

""" 

return not self == other 

 

def _repr_(self): 

r""" 

Returns a printable version of the operation table. 

 

EXAMPLES:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: R=Integers(5) 

sage: T=OperationTable(R, operation=operator.add) 

sage: print(T._repr_()) 

+ a b c d e 

+---------- 

a| a b c d e 

b| b c d e a 

c| c d e a b 

d| d e a b c 

e| e a b c d 

""" 

return self._ascii_table() 

 

def set_print_symbols(self, ascii, latex): 

r""" 

Set the symbols used for text and LaTeX printing of operation tables. 

 

INPUT: 

 

- ``ascii`` - a single character for text table 

- ``latex`` - a string to represent an operation in LaTeX math mode. 

Note the need for double-backslashes to escape properly. 

 

EXAMPLES:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=AlternatingGroup(3) 

sage: T=OperationTable(G, operator.mul) 

sage: T.set_print_symbols('@', '\\times') 

sage: T 

@ a b c 

+------ 

a| a b c 

b| b c a 

c| c a b 

sage: T._latex_() 

'{\\setlength{\\arraycolsep}{2ex}\n\\begin{array}{r|*{3}{r}}\n\\multicolumn{1}{c|}{\\times}&a&b&c\\\\\\hline\n{}a&a&b&c\\\\\n{}b&b&c&a\\\\\n{}c&c&a&b\\\\\n\\end{array}}' 

 

TESTS:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=AlternatingGroup(3) 

sage: T=OperationTable(G, operator.mul) 

sage: T.set_print_symbols('@', 5) 

Traceback (most recent call last): 

... 

ValueError: LaTeX symbol must be a string, not 5 

sage: T.set_print_symbols('@x@', '\\times') 

Traceback (most recent call last): 

... 

ValueError: ASCII symbol should be a single character, not @x@ 

sage: T.set_print_symbols(5, '\\times') 

Traceback (most recent call last): 

... 

ValueError: ASCII symbol should be a single character, not 5 

""" 

if not isinstance(ascii, six.string_types) or not len(ascii)==1: 

raise ValueError('ASCII symbol should be a single character, not %s' % ascii) 

if not isinstance(latex, six.string_types): 

raise ValueError('LaTeX symbol must be a string, not %s' % latex) 

self._ascii_symbol = ascii 

self._latex_symbol = latex 

return None 

 

def column_keys(self): 

r""" 

Returns a tuple of the elements used to build the table. 

 

.. note:: ``column_keys`` and ``row_keys`` are identical. 

Both list the elements in the order used to label the table. 

 

OUTPUT: 

 

The elements of the algebraic structure used to build 

the table, as a list. But most importantly, elements are 

present in the list in the order which they appear in 

the table's column headings. 

 

EXAMPLES:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=AlternatingGroup(3) 

sage: T=OperationTable(G, operator.mul) 

sage: T.column_keys() 

((), (1,2,3), (1,3,2)) 

""" 

return self._elts 

 

# The ordered list of row and column elements are identical 

# given the current design, so these methods are aliases. If 

# expanded to allow different orderings (maybe interesting in 

# non-commutative cases?), then these will need to be 

# implemented separately. 

row_keys = column_keys 

 

def translation(self): 

r""" 

Returns a dictionary associating names with elements. 

 

OUTPUT: 

A dictionary whose keys are strings used as names 

for entries of the table and values that are the 

actual elements of the algebraic structure. 

 

EXAMPLES:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=AlternatingGroup(3) 

sage: T=OperationTable(G, operator.mul, names=['p','q','r']) 

sage: sorted(T.translation().items()) 

[('p', ()), ('q', (1,2,3)), ('r', (1,3,2))] 

""" 

return self._name_dict 

 

def table(self): 

r""" 

Returns the table as a list of lists, 

using integers to reference the elements. 

 

OUTPUT: 

The rows of the table, as a list of rows, each row 

being a list of integer entries. The integers correspond 

to the order of the elements in the headings of the table 

and the order of the output of the :meth:`list` method. 

 

EXAMPLES:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: C=CyclicPermutationGroup(3) 

sage: T=OperationTable(C, operator.mul) 

sage: T.table() 

[[0, 1, 2], [1, 2, 0], [2, 0, 1]] 

""" 

return self._table 

 

def change_names(self, names): 

r""" 

For an existing operation table, change the names used for the elements. 

 

INPUT: 

 

- ``names`` - the type of names used, values are: 

 

* ``'letters'`` - lowercase ASCII letters are used 

for a base 26 representation of the elements' 

positions in the list given by :meth:`list`, 

padded to a common width with leading 'a's. 

* ``'digits'`` - base 10 representation of the 

elements' positions in the list given by 

:meth:`list`, padded to a common width 

with leading zeros. 

* ``'elements'`` - the string representations 

of the elements themselves. 

* a list - a list of strings, where the length 

of the list equals the number of elements. 

 

OUTPUT: 

``None``. This method changes the table "in-place", 

so any printed version will change and the output of 

the :meth:`dict` will also change. So any items of 

interest about a particular table need to be copied/saved 

prior to calling this method. 

 

EXAMPLES: 

 

More examples can be found in the documentation for 

:class:`OperationTable` since creating a new 

operation table uses the same routine. :: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: D=DihedralGroup(2) 

sage: T=OperationTable(D, operator.mul) 

sage: T 

* a b c d 

+-------- 

a| a b c d 

b| b a d c 

c| c d a b 

d| d c b a 

sage: T.translation()['c'] 

(1,2) 

sage: T.change_names('digits') 

sage: T 

* 0 1 2 3 

+-------- 

0| 0 1 2 3 

1| 1 0 3 2 

2| 2 3 0 1 

3| 3 2 1 0 

sage: T.translation()['2'] 

(1,2) 

sage: T.change_names('elements') 

sage: T 

* () (3,4) (1,2) (1,2)(3,4) 

+-------------------------------------------- 

()| () (3,4) (1,2) (1,2)(3,4) 

(3,4)| (3,4) () (1,2)(3,4) (1,2) 

(1,2)| (1,2) (1,2)(3,4) () (3,4) 

(1,2)(3,4)| (1,2)(3,4) (1,2) (3,4) () 

sage: T.translation()['(1,2)'] 

(1,2) 

sage: T.change_names(['w', 'x', 'y', 'z']) 

sage: T 

* w x y z 

+-------- 

w| w x y z 

x| x w z y 

y| y z w x 

z| z y x w 

sage: T.translation()['y'] 

(1,2) 

""" 

self._width, self._names, self._name_dict = self._name_maker(names) 

return None 

 

def matrix_of_variables(self): 

r""" 

This method provides some backward compatibility for 

Cayley tables of groups, whose output was 

restricted to this single format. 

 

EXAMPLES: 

 

The output here is from the doctests for the old 

``cayley_table()`` method for permutation groups. :: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: G=PermutationGroup(['(1,2,3)', '(2,3)']) 

sage: T=OperationTable(G, operator.mul) 

sage: T.matrix_of_variables() 

[x0 x1 x2 x3 x4 x5] 

[x1 x0 x3 x2 x5 x4] 

[x2 x5 x4 x1 x0 x3] 

[x3 x4 x5 x0 x1 x2] 

[x4 x3 x0 x5 x2 x1] 

[x5 x2 x1 x4 x3 x0] 

sage: T.column_keys()[3]*T.column_keys()[3] == T.column_keys()[0] 

True 

""" 

from sage.rings.polynomial.polynomial_ring_constructor import PolynomialRing 

from sage.matrix.matrix_space import MatrixSpace 

from sage.rings.rational_field import QQ 

R = PolynomialRing(QQ, 'x', self._n) 

MS = MatrixSpace(R, self._n, self._n) 

entries = [R('x'+str(self._table[i][j])) for i in range(self._n) for j in range(self._n)] 

return MS( entries ) 

 

#def color_table(): 

#r""" 

#Returns a graphic image as a square grid where entries are color coded. 

#""" 

#pass 

#return None 

 

#def gray_table(): 

#r""" 

#Returns a graphic image as a square grid where entries are coded as grayscale values. 

#""" 

#pass 

#return None 

 

def _ascii_table(self): 

r""" 

Returns a string that is an ASCII version of the table. 

 

EXAMPLES:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: R=Integers(5) 

sage: T=OperationTable(R, operator.add) 

sage: print(T._ascii_table()) 

+ a b c d e 

+---------- 

a| a b c d e 

b| b c d e a 

c| c d e a b 

d| d e a b c 

e| e a b c d 

 

The table should adjust its column width to accomodate the width of the 

strings used to represent elements. :: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: R=Integers(10) 

sage: T=OperationTable(R, operator.mul, names='digits') 

sage: print(T._ascii_table()) 

* 0 1 2 3 4 5 6 7 8 9 

+-------------------- 

0| 0 0 0 0 0 0 0 0 0 0 

1| 0 1 2 3 4 5 6 7 8 9 

2| 0 2 4 6 8 0 2 4 6 8 

3| 0 3 6 9 2 5 8 1 4 7 

4| 0 4 8 2 6 0 4 8 2 6 

5| 0 5 0 5 0 5 0 5 0 5 

6| 0 6 2 8 4 0 6 2 8 4 

7| 0 7 4 1 8 5 2 9 6 3 

8| 0 8 6 4 2 0 8 6 4 2 

9| 0 9 8 7 6 5 4 3 2 1 

 

:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: R=Integers(11) 

sage: T=OperationTable(R, operator.mul, names='digits') 

sage: print(T._ascii_table()) 

* 00 01 02 03 04 05 06 07 08 09 10 

+--------------------------------- 

00| 00 00 00 00 00 00 00 00 00 00 00 

01| 00 01 02 03 04 05 06 07 08 09 10 

02| 00 02 04 06 08 10 01 03 05 07 09 

03| 00 03 06 09 01 04 07 10 02 05 08 

04| 00 04 08 01 05 09 02 06 10 03 07 

05| 00 05 10 04 09 03 08 02 07 01 06 

06| 00 06 01 07 02 08 03 09 04 10 05 

07| 00 07 03 10 06 02 09 05 01 08 04 

08| 00 08 05 02 10 07 04 01 09 06 03 

09| 00 09 07 05 03 01 10 08 06 04 02 

10| 00 10 09 08 07 06 05 04 03 02 01 

 

:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: R=Integers(4) 

sage: T=OperationTable(R, operator.mul, names=['x','y','wwww', 'z']) 

sage: print(T._ascii_table()) 

* x y wwww z 

+-------------------- 

x| x x x x 

y| x y wwww z 

wwww| x wwww x wwww 

z| x z wwww y 

""" 

n = self._n 

width = self._width 

 

widenames = [] 

for name in self._names: 

widenames.append('{0: >{1}s}'.format(name, width)) 

 

# Headers 

table = ['{0: >{1}s} '.format(self._ascii_symbol,width)] 

table += [' '+widenames[i] for i in range(n)]+['\n'] 

table += [' ']*width + ['+'] + ['-']*(n*(width+1))+['\n'] 

 

# Row labels, body of table 

for g in range(n): 

table.append(widenames[g]+'|') 

for h in range(n): 

table.append(' '+widenames[self._table[g][h]]) 

table.append('\n') 

return ''.join(table) 

 

def _latex_(self): 

r""" 

Returns a `LaTeX` version of the operation table as a string, 

using a `LaTeX` ``array`` environment. 

 

EXAMPLES:: 

 

sage: from sage.matrix.operation_table import OperationTable 

sage: R=Integers(2) 

sage: T=OperationTable(R, operation=operator.mul) 

sage: T._latex_() 

'{\\setlength{\\arraycolsep}{2ex}\n\\begin{array}{r|*{2}{r}}\n\\multicolumn{1}{c|}{\\ast}&a&b\\\\\\hline\n{}a&a&a\\\\\n{}b&a&b\\\\\n\\end{array}}' 

""" 

n = self._n 

names = self._names 

 

# Headers 

table = ['{\\setlength{\\arraycolsep}{2ex}\n'] 

table.append('\\begin{array}{r|*{'+str(n)+'}{r}}\n') 

table.append('\\multicolumn{1}{c|}{'+self._latex_symbol+'}') 

table += ['&'+names[i] for i in range(n)] 

table.append('\\\\\\hline\n') 

 

# Row label and body of table 

for g in range(n): 

table.append('{}') # Interrupts newline and [], so not line spacing 

table.append(names[g]) 

for h in range(n): 

table.append('&'+names[self._table[g][h]]) 

table.append('\\\\\n') 

 

# Finish 

table.append('\\end{array}') 

table.append('}') 

return ''.join(table)