aboutsummaryrefslogtreecommitdiff
path: root/src/algebra/pfo.spad.pamphlet
blob: 970c8c98e88f96ba912e3beb223f981ede559129 (plain)
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
\documentclass{article}
\usepackage{open-axiom}
\begin{document}
\title{\$SPAD/src/algebra pfo.spad}
\author{Manuel Bronstein}
\maketitle
\begin{abstract}
\end{abstract}
\eject
\tableofcontents
\eject
\section{package FORDER FindOrderFinite}
<<package FORDER FindOrderFinite>>=
)abbrev package FORDER FindOrderFinite
++ Finds the order of a divisor over a finite field
++ Author: Manuel Bronstein
++ Date Created: 1988
++ Date Last Updated: 11 Jul 1990
FindOrderFinite(F, UP, UPUP, R): Exports == Implementation where
  F   : Join(Finite, Field)
  UP  : UnivariatePolynomialCategory F
  UPUP: UnivariatePolynomialCategory Fraction UP
  R   : FunctionFieldCategory(F, UP, UPUP)

  Exports ==> with
    order: FiniteDivisor(F, UP, UPUP, R) -> NonNegativeInteger
	++ order(x) \undocumented
  Implementation ==> add
    order d ==
      dd := d := reduce d
      for i in 1.. repeat
        principal? dd => return(i::NonNegativeInteger)
        dd := reduce(d + dd)

@
\section{package RDIV ReducedDivisor}
<<package RDIV ReducedDivisor>>=
)abbrev package RDIV ReducedDivisor
++ Finds the order of a divisor over a finite field
++ Author: Manuel Bronstein
++ Date Created: 1988
++ Date Last Updated: 8 November 1994
ReducedDivisor(F1, UP, UPUP, R, F2): Exports == Implementation where
  F1    : Field
  UP    : UnivariatePolynomialCategory F1
  UPUP  : UnivariatePolynomialCategory Fraction UP
  R     : FunctionFieldCategory(F1, UP, UPUP)
  F2    : Join(Finite, Field)

  N     ==> NonNegativeInteger
  FD    ==> FiniteDivisor(F1, UP, UPUP, R)
  UP2   ==> SparseUnivariatePolynomial F2
  UPUP2 ==> SparseUnivariatePolynomial Fraction UP2

  Exports ==> with
    order: (FD, UPUP, F1 -> F2) -> N
	++ order(f,u,g) \undocumented

  Implementation ==> add
    algOrder : (FD, UPUP, F1 -> F2)  -> N
    rootOrder: (FD, UP, N, F1 -> F2) -> N

-- pp is not necessarily monic
    order(d, pp, f) ==
      (r := retractIfCan(reductum pp)@Union(Fraction UP, "failed"))
        case "failed" => algOrder(d, pp, f)
      rootOrder(d, - retract(r::Fraction(UP) / leadingCoefficient pp)@UP,
                degree pp, f)

    algOrder(d, modulus, reduce) ==
      redmod := map(reduce, modulus)$MultipleMap(F1,UP,UPUP,F2,UP2,UPUP2)
      curve  := AlgebraicFunctionField(F2, UP2, UPUP2, redmod)
      order(map(reduce,
              d)$FiniteDivisorFunctions2(F1,UP,UPUP,R,F2,UP2,UPUP2,curve)
                                 )$FindOrderFinite(F2, UP2, UPUP2, curve)

    rootOrder(d, radicand, n, reduce) ==
      redrad := map(reduce,
           radicand)$UnivariatePolynomialCategoryFunctions2(F1,UP,F2,UP2)
      curve  := RadicalFunctionField(F2, UP2, UPUP2, redrad::Fraction UP2, n)
      order(map(reduce,
              d)$FiniteDivisorFunctions2(F1,UP,UPUP,R,F2,UP2,UPUP2,curve)
                                 )$FindOrderFinite(F2, UP2, UPUP2, curve)

@
\section{package PFOTOOLS PointsOfFiniteOrderTools}
<<package PFOTOOLS PointsOfFiniteOrderTools>>=
)abbrev package PFOTOOLS PointsOfFiniteOrderTools
++ Utilities for PFOQ and PFO
++ Author: Manuel Bronstein
++ Date Created: 25 Aug 1988
++ Date Last Updated: 11 Jul 1990
PointsOfFiniteOrderTools(UP, UPUP): Exports == Implementation where
  UP   : UnivariatePolynomialCategory Fraction Integer
  UPUP : UnivariatePolynomialCategory Fraction UP

  PI  ==> PositiveInteger
  N   ==> NonNegativeInteger
  Z   ==> Integer
  Q   ==> Fraction Integer

  Exports ==> with
    getGoodPrime : Z -> PI
      ++ getGoodPrime n returns the smallest prime not dividing n
    badNum       : UP   -> Record(den:Z, gcdnum:Z)
	++ badNum(p) \undocumented
    badNum       : UPUP -> Z
	++ badNum(u) \undocumented
    mix          : List Record(den:Z, gcdnum:Z) -> Z
	++ mix(l) \undocumented
    doubleDisc   : UPUP -> Z
	++ doubleDisc(u) \undocumented
    polyred      : UPUP -> UPUP
	++ polyred(u) \undocumented

  Implementation ==> add
    import IntegerPrimesPackage(Z)
    import UnivariatePolynomialCommonDenominator(Z, Q, UP)

    mix l          == lcm(lcm [p.den for p in l], gcd [p.gcdnum for p in l])
    badNum(p:UPUP) == mix [badNum(retract(c)@UP) for c in coefficients p]

    polyred r ==
      lcm [commonDenominator(retract(c)@UP) for c in coefficients r] * r

    badNum(p:UP) ==
      cd := splitDenominator p
      [cd.den, gcd [retract(c)@Z for c in coefficients(cd.num)]]

    getGoodPrime n ==
      p:PI := 3
      while zero?(n rem p) repeat
        p := nextPrime(p::Z)::PI
      p

    doubleDisc r ==
      d := retract(discriminant r)@UP
      retract(discriminant((d exquo gcd(d, differentiate d))::UP))@Z

@
\section{package PFOQ PointsOfFiniteOrderRational}
<<package PFOQ PointsOfFiniteOrderRational>>=
)abbrev package PFOQ PointsOfFiniteOrderRational
++ Finds the order of a divisor on a rational curve
++ Author: Manuel Bronstein
++ Date Created: 25 Aug 1988
++ Date Last Updated: 3 August 1993
++ Description:
++ This package provides function for testing whether a divisor on a
++ curve is a torsion divisor.
++ Keywords: divisor, algebraic, curve.
++ Examples: )r PFOQ INPUT
PointsOfFiniteOrderRational(UP, UPUP, R): Exports == Implementation where
  UP   : UnivariatePolynomialCategory Fraction Integer
  UPUP : UnivariatePolynomialCategory Fraction UP
  R    : FunctionFieldCategory(Fraction Integer, UP, UPUP)

  PI  ==> PositiveInteger
  N   ==> NonNegativeInteger
  Z   ==> Integer
  Q   ==> Fraction Integer
  FD  ==> FiniteDivisor(Q, UP, UPUP, R)

  Exports ==> with
    order       : FD -> Union(N, "failed")
	++ order(f) \undocumented
    torsion?    : FD -> Boolean
	++ torsion?(f) \undocumented
    torsionIfCan: FD -> Union(Record(order:N, function:R), "failed")
	++ torsionIfCan(f) \undocumented

  Implementation ==> add
    import PointsOfFiniteOrderTools(UP, UPUP)

    possibleOrder: FD -> N
    ratcurve     : (FD, UPUP, Z) -> N
    rat          : (UPUP, FD, PI) -> N

    torsion? d  == order(d) case N

-- returns the potential order of d, 0 if d is of infinite order
    ratcurve(d, modulus, disc) ==
      mn  := minIndex(nm := numer(i := ideal d))
      h   := lift(hh := nm(mn + 1))
      s   := separate(retract(norm hh)@UP,
               b := retract(retract(nm.mn)@Fraction(UP))@UP).primePart
      bd  := badNum denom i
      r   := resultant(s, b)
      bad := lcm [disc, numer r, denom r, bd.den * bd.gcdnum, badNum h]$List(Z)
      n   := rat(modulus, d, p := getGoodPrime bad)
-- if n > 1 then it is cheaper to compute the order modulo a second prime,
-- since computing n * d could be very expensive
      one? n => n
      m   := rat(modulus, d, getGoodPrime(p * bad))
      n = m => n
      0

    rat(pp, d, p) ==
      gf := InnerPrimeField p
      order(d, pp,
        numer(#1)::gf / denom(#1)::gf)$ReducedDivisor(Q, UP, UPUP, R, gf)

-- returns the potential order of d, 0 if d is of infinite order
    possibleOrder d ==
      zero?(genus()) or one?(#(numer ideal d)) => 1
      r := polyred definingPolynomial()$R
      ratcurve(d, r, doubleDisc r)

    order d ==
      zero?(n := possibleOrder(d := reduce d)) => "failed"
      principal? reduce(n::Z * d) => n
      "failed"

    torsionIfCan d ==
      zero?(n := possibleOrder(d := reduce d)) => "failed"
      (g := generator reduce(n::Z * d)) case "failed" => "failed"
      [n, g::R]

@
\section{package FSRED FunctionSpaceReduce}
<<package FSRED FunctionSpaceReduce>>=
)abbrev package FSRED FunctionSpaceReduce
++ Reduction from a function space to the rational numbers
++ Author: Manuel Bronstein
++ Date Created: 1988
++ Date Last Updated: 11 Jul 1990
++ Description:
++ This package provides function which replaces transcendental kernels
++ in a function space by random integers. The correspondence between
++ the kernels and the integers is fixed between calls to new().
++ Keywords: function, space, redcution.
FunctionSpaceReduce(R, F): Exports == Implementation where
  R: Join(IntegralDomain, RetractableTo Integer)
  F: FunctionSpace R

  Z   ==> Integer
  Q   ==> Fraction Integer
  UP  ==> SparseUnivariatePolynomial Q
  K   ==> Kernel F

  Exports ==> with
    bringDown: F -> Q
	++ bringDown(f) \undocumented
    bringDown: (F, K) -> UP
	++ bringDown(f,k) \undocumented
    newReduc : () -> Void
	++ newReduc() \undocumented

  Implementation ==> add
    macro ALGOP  == '%alg
    import SparseUnivariatePolynomialFunctions2(F, Q)
    import PolynomialCategoryQuotientFunctions(IndexedExponents K,
                         K, R, SparseMultivariatePolynomial(R, K), F)

    K2Z : K -> F

    redmap := table()$AssociationList(K, Z)

    newReduc() ==
      for k in keys redmap repeat remove!(k, redmap)

    bringDown(f, k) ==
      ff := univariate(f, k)
      (bc := extendedEuclidean(map(bringDown, denom ff),
                m := map(bringDown, minPoly k), 1)) case "failed" =>
                     error "denominator is 0"
      (map(bringDown, numer ff) * bc.coef1) rem m

    bringDown f ==
      retract(eval(f, lk := kernels f, [K2Z k for k in lk]))@Q

    K2Z k ==
      has?(operator k, ALGOP) => error "Cannot reduce constant field"
      (u := search(k, redmap)) case "failed" =>
                                      setelt(redmap, k, random()$Z)::F
      u::Z::F

@
\section{package PFO PointsOfFiniteOrder}
<<package PFO PointsOfFiniteOrder>>=
)abbrev package PFO PointsOfFiniteOrder
++ Finds the order of a divisor on a curve
++ Author: Manuel Bronstein
++ Date Created: 1988
++ Date Last Updated: 22 July 1998
++ Description:
++ This package provides function for testing whether a divisor on a
++ curve is a torsion divisor.
++ Keywords: divisor, algebraic, curve.
++ Examples: )r PFO INPUT
PointsOfFiniteOrder(R0, F, UP, UPUP, R): Exports == Implementation where
  R0   : Join(IntegralDomain, RetractableTo Integer)
  F    : FunctionSpace R0
  UP   : UnivariatePolynomialCategory F
  UPUP : UnivariatePolynomialCategory Fraction UP
  R    : FunctionFieldCategory(F, UP, UPUP)

  PI  ==> PositiveInteger
  N   ==> NonNegativeInteger
  Z   ==> Integer
  Q   ==> Fraction Integer
  UPF ==> SparseUnivariatePolynomial F
  UPQ ==> SparseUnivariatePolynomial Q
  QF  ==> Fraction UP
  UPUPQ ==> SparseUnivariatePolynomial Fraction UPQ
  UP2 ==> SparseUnivariatePolynomial UPQ
  UP3 ==> SparseUnivariatePolynomial UP2
  FD  ==> FiniteDivisor(F, UP, UPUP, R)
  K   ==> Kernel F
  REC ==> Record(ncurve:UP3, disc:Z, dfpoly:UPQ)
  RC0 ==> Record(ncurve:UPUPQ, disc:Z)
  ID  ==> FractionalIdeal(UP, QF, UPUP, R)
  SMP ==> SparseMultivariatePolynomial(R0,K)

  Exports ==> with
    order        : FD -> Union(N, "failed")
	++ order(f) \undocumented
    torsion?     : FD -> Boolean
	++ torsion?(f) \undocumented
    torsionIfCan : FD -> Union(Record(order:N, function:R), "failed")
	++ torsionIfCan(f)\ undocumented

  Implementation ==> add
    macro ALGOP == '%alg
    import IntegerPrimesPackage(Z)
    import PointsOfFiniteOrderTools(UPQ, UPUPQ)
    import UnivariatePolynomialCommonDenominator(Z, Q, UPQ)

    cmult: List SMP -> SMP
    raise         : (UPQ, K) -> F
    raise2        : (UP2, K) -> UP
    qmod          : F     -> Q
    fmod          : UPF   -> UPQ
    rmod          : UP    -> UPQ
    pmod          : UPUP  -> UPUPQ
    kqmod         : (F,    K) -> UPQ
    krmod         : (UP,   K) -> UP2
    kpmod         : (UPUP, K) -> UP3
    selectIntegers: K   -> REC
    selIntegers:    ()  -> RC0
    possibleOrder : FD -> N
    ratcurve      : (FD, RC0)    -> N
    algcurve      : (FD, REC, K) -> N
    kbad3Num      : (UP3, UPQ) -> Z
    kbadBadNum    : (UP2, UPQ) -> Z
    kgetGoodPrime : (REC, UPQ, UP3, UP2,UP2) -> Record(prime:PI,poly:UPQ)
    goodRed       : (REC, UPQ, UP3, UP2, UP2, PI) -> Union(UPQ, "failed")
    good?         : (UPQ, UP3, UP2, UP2, PI, UPQ) -> Boolean
    klist         : UP -> List K
    aklist        : R  -> List K
    alglist       : FD -> List K
    notIrr?       : UPQ -> Boolean
    rat           : (UPUP, FD, PI) -> N
    toQ1          : (UP2, UPQ) -> UP
    toQ2          : (UP3, UPQ) -> R
    Q2F           : Q -> F
    Q2UPUP        : UPUPQ -> UPUP

    q := FunctionSpaceReduce(R0, F)

    torsion? d == order(d) case N
    Q2F x      == numer(x)::F / denom(x)::F
    qmod x     == bringDown(x)$q
    kqmod(x,k) == bringDown(x, k)$q
    fmod p     == map(qmod, p)$SparseUnivariatePolynomialFunctions2(F, Q)
    pmod p     == map(qmod, p)$MultipleMap(F, UP, UPUP, Q, UPQ, UPUPQ)
    Q2UPUP p   == map(Q2F, p)$MultipleMap(Q, UPQ, UPUPQ, F, UP, UPUP)
    klist d    == "setUnion"/[kernels c for c in coefficients d]
    notIrr? d  == #(factors factor(d)$RationalFactorize(UPQ)) > 1
    kbadBadNum(d, m) == mix [badNum(c rem m) for c in coefficients d]
    kbad3Num(h, m)   == lcm [kbadBadNum(c, m) for c in coefficients h]
    
    torsionIfCan d ==
      zero?(n := possibleOrder(d := reduce d)) => "failed"
      (g := generator reduce(n::Z * d)) case "failed" => "failed"
      [n, g::R]

    UPQ2F(p:UPQ, k:K):F ==
      map(Q2F, p)$UnivariatePolynomialCategoryFunctions2(Q, UPQ, F, UP) (k::F)

    UP22UP(p:UP2, k:K):UP ==
      map(UPQ2F(#1, k), p)$UnivariatePolynomialCategoryFunctions2(UPQ,UP2,F,UP)

    UP32UPUP(p:UP3, k:K):UPUP ==
      map(UP22UP(#1,k)::QF,
          p)$UnivariatePolynomialCategoryFunctions2(UP2, UP3, QF, UPUP)

    cmult(l:List SMP):SMP ==
      R0 has GcdDomain => lcm l
      */l

    doubleDisc(f:UP3):Z ==
      d := discriminant f
      g := gcd(d, differentiate d)
      d := (d exquo g)::UP2
      zero?(e := discriminant d) => 0
      gcd [retract(c)@Z for c in coefficients e]

    commonDen(p:UP):SMP ==
      l1:List F := coefficients p
      l2:List SMP := [denom c for c in l1]
      cmult l2

    polyred(f:UPUP):UPUP ==
      cmult([commonDen(retract(c)@UP) for c in coefficients f])::F::UP::QF * f

    aklist f ==
      (r := retractIfCan(f)@Union(QF, "failed")) case "failed" =>
        "setUnion"/[klist(retract(c)@UP) for c in coefficients lift f]
      klist(retract(r::QF)@UP)

    alglist d ==
      n := numer(i := ideal d)
      select!(has?(operator #1, ALGOP),
               setUnion(klist denom i,
                 "setUnion"/[aklist qelt(n,i) for i in minIndex n..maxIndex n]))

    krmod(p,k) ==
       map(kqmod(#1, k),
           p)$UnivariatePolynomialCategoryFunctions2(F, UP, UPQ, UP2)

    rmod p ==
       map(qmod, p)$UnivariatePolynomialCategoryFunctions2(F, UP, Q, UPQ)

    raise(p, k) ==
      (map(Q2F, p)$SparseUnivariatePolynomialFunctions2(Q, F)) (k::F)

    raise2(p, k) ==
      map(raise(#1, k),
          p)$UnivariatePolynomialCategoryFunctions2(UPQ, UP2, F, UP)

    algcurve(d, rc, k) ==
      mn := minIndex(n := numer(i := minimize ideal d))
      h  := kpmod(lift(hh := n(mn + 1)), k)
      b2 := primitivePart
                 raise2(b := krmod(retract(retract(n.mn)@QF)@UP, k), k)
      s  := kqmod(resultant(primitivePart separate(raise2(krmod(
                    retract(norm hh)@UP, k), k), b2).primePart, b2), k)
      pr := kgetGoodPrime(rc, s, h, b, dd := krmod(denom i, k))
      p  := pr.prime
      pp := UP32UPUP(rc.ncurve, k)
      mm := pr.poly
      gf := InnerPrimeField p
      m  := map(retract(#1)@Z :: gf,
                         mm)$SparseUnivariatePolynomialFunctions2(Q, gf)
      one? degree m =>
        alpha := - coefficient(m, 0) / leadingCoefficient m
        order(d, pp,
           (map(numer(#1)::gf / denom(#1)::gf,
            kqmod(#1,k))$SparseUnivariatePolynomialFunctions2(Q,gf))(alpha)
                                   )$ReducedDivisor(F, UP, UPUP, R, gf)
        -- d1 := toQ1(dd, mm)
        -- rat(pp, divisor ideal([(toQ1(b, mm) / d1)::QF::R,
                                       -- inv(d1::QF) * toQ2(h,mm)])$ID, p)
      sae:= SimpleAlgebraicExtension(gf,SparseUnivariatePolynomial gf,m)
      order(d, pp,
           reduce(map(numer(#1)::gf / denom(#1)::gf,
            kqmod(#1,k))$SparseUnivariatePolynomialFunctions2(Q,gf))$sae
                                   )$ReducedDivisor(F, UP, UPUP, R, sae)

-- returns the potential order of d, 0 if d is of infinite order
    ratcurve(d, rc) ==
      mn  := minIndex(nm := numer(i := minimize ideal d))
      h   := pmod lift(hh := nm(mn + 1))
      b   := rmod(retract(retract(nm.mn)@QF)@UP)
      s   := separate(rmod(retract(norm hh)@UP), b).primePart
      bd  := badNum rmod denom i
      r   := resultant(s, b)
      bad := lcm [rc.disc, numer r, denom r, bd.den*bd.gcdnum, badNum h]$List(Z)
      pp  := Q2UPUP(rc.ncurve)
      n   := rat(pp, d, p := getGoodPrime bad)
-- if n > 1 then it is cheaper to compute the order modulo a second prime,
-- since computing n * d could be very expensive
      one? n => n
      m   := rat(pp, d, getGoodPrime(p * bad))
      n = m => n
      0

-- returns the order of d mod p
    rat(pp, d, p) ==
      gf := InnerPrimeField p
      order(d, pp, (qq := qmod #1;numer(qq)::gf / denom(qq)::gf)
                                    )$ReducedDivisor(F, UP, UPUP, R, gf)

-- returns the potential order of d, 0 if d is of infinite order
    possibleOrder d ==
      zero?(genus()) or one?(#(numer ideal d)) => 1
      empty?(la := alglist d) => ratcurve(d, selIntegers())
      not(empty? rest la) =>
           error "PFO::possibleOrder: more than 1 algebraic constant"
      algcurve(d, selectIntegers first la, first la)

    selIntegers():RC0 ==
      f := definingPolynomial()$R
      repeat
        r := polyred pmod f
        d := doubleDisc r
        if zero? d then
          newReduc()$q
        else
          return [r,d]

    selectIntegers(k:K):REC ==
      g := polyred(f := definingPolynomial()$R)
      p := minPoly k
      repeat
        r := kpmod(g, k)
        d := doubleDisc r
        if zero? d or notIrr? fmod p then
          newReduc()$q
        else
          return [r, d, splitDenominator(fmod p).num]

    toQ1(p, d) ==
      map(Q2F(retract(#1 rem d)@Q),
          p)$UnivariatePolynomialCategoryFunctions2(UPQ, UP2, F, UP)

    toQ2(p, d) ==
      reduce map(toQ1(#1, d)::QF,
        p)$UnivariatePolynomialCategoryFunctions2(UP2, UP3, QF, UPUP)

    kpmod(p, k) ==
      map(krmod(retract(#1)@UP, k),
        p)$UnivariatePolynomialCategoryFunctions2(QF, UPUP, UP2, UP3)

    order d ==
      zero?(n := possibleOrder(d := reduce d)) => "failed"
      principal? reduce(n::Z * d) => n
      "failed"

    kgetGoodPrime(rec, res, h, b, d) ==
      p:PI := 3
      u : Union(UPQ, "failed")
      while (u := goodRed(rec, res, h, b, d, p)) case "failed" repeat
        p := nextPrime(p::Z)::PI
      [p, u::UPQ]

    goodRed(rec, res, h, b, d, p) ==
      zero?(rec.disc rem p) => "failed"
      gf := InnerPrimeField p
      l  := [f.factor for f in factors factor(map(retract(#1)@Z :: gf,
               rec.dfpoly)$SparseUnivariatePolynomialFunctions2(Q,
                 gf))$DistinctDegreeFactorize(gf,
                   SparseUnivariatePolynomial gf) | one?(f.exponent)]
      empty? l => "failed"
      mdg := first l
      for ff in rest l repeat
        if degree(ff) < degree(mdg) then mdg := ff
      md := map(convert(#1)@Z :: Q,
                 mdg)$SparseUnivariatePolynomialFunctions2(gf, Q)
      good?(res, h, b, d, p, md) => md
      "failed"

    good?(res, h, b, d, p, m) ==
      bd := badNum(res rem m)
      not (zero?(bd.den rem p) or zero?(bd.gcdnum rem p) or
        zero?(kbadBadNum(b,m) rem p) or zero?(kbadBadNum(d,m) rem p)
              or zero?(kbad3Num(h, m) rem p))

@
\section{License}
<<license>>=
--Copyright (c) 1991-2002, The Numerical ALgorithms Group Ltd.
--All rights reserved.
-- Copyright (C) 2007-2010, Gabriel Dos Reis.
-- All rights reserved.
--
--Redistribution and use in source and binary forms, with or without
--modification, are permitted provided that the following conditions are
--met:
--
--    - Redistributions of source code must retain the above copyright
--      notice, this list of conditions and the following disclaimer.
--
--    - Redistributions in binary form must reproduce the above copyright
--      notice, this list of conditions and the following disclaimer in
--      the documentation and/or other materials provided with the
--      distribution.
--
--    - Neither the name of The Numerical ALgorithms Group Ltd. nor the
--      names of its contributors may be used to endorse or promote products
--      derived from this software without specific prior written permission.
--
--THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
--IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
--TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
--PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
--OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
--EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
--PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
--PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
--LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
--NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
--SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
@
<<*>>=
<<license>>

-- SPAD files for the integration world should be compiled in the
-- following order:
--
--   intaux  rderf  intrf  curve  curvepkg  divisor  PFO
--   intalg  intaf  efstruc  rdeef  intef  irexpand  integrat

<<package FORDER FindOrderFinite>>
<<package RDIV ReducedDivisor>>
<<package PFOTOOLS PointsOfFiniteOrderTools>>
<<package PFOQ PointsOfFiniteOrderRational>>
<<package FSRED FunctionSpaceReduce>>
<<package PFO PointsOfFiniteOrder>>
@
\eject
\begin{thebibliography}{99}
\bibitem{1} nothing
\end{thebibliography}
\end{document}