aboutsummaryrefslogtreecommitdiff
path: root/src/algebra/list.spad.pamphlet
blob: f97baab6313decad5f8007049dc2a530d0f49e32 (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
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
\documentclass{article}
\usepackage{open-axiom}
\begin{document}
\title{src/algebra list.spad}
\author{Michael Monagon, Manuel Bronstein}
\maketitle

\begin{abstract}
\end{abstract}
\tableofcontents
\eject

\section{domain ILIST IndexedList}

<<domain ILIST IndexedList>>=
import Type
import ListAggregate
)abbrev domain ILIST IndexedList
++ Author: Michael Monagan
++ Date Created: Sep 1987
++ Change History:
++ Basic Operations:
++   \#, concat, concat!, construct, copy, elt, elt, empty,
++   empty?, eq?, first, member?, merge!, mergeSort, minIndex,
++   parts, removeDuplicates!, rest, rest, reverse, reverse!,
++   setelt, setfirst!, setrest!, sort!, split!
++ Related Constructors: List
++ Also See:
++ AMS Classification:
++ Keywords: list, aggregate, index
++ Description:
++   \spadtype{IndexedList} is a basic implementation of the functions
++   in \spadtype{ListAggregate}, often using functions in the underlying
++   LISP system. The second parameter to the constructor (\spad{mn})
++   is the beginning index of the list. That is, if \spad{l} is a
++   list, then \spad{elt(l,mn)} is the first value. This constructor
++   is probably best viewed as the implementation of singly-linked
++   lists that are addressable by index rather than as a mere wrapper
++   for LISP lists.
IndexedList(S:Type, mn:Integer): Exports == Implementation where
 cycleMax ==> 1000        -- value used in checking for cycles

-- The following seems to be a bit out of date, but is kept in case
-- a knowledgeable person wants to update it:
--   The following LISP dependencies are divided into two groups
--   Those that are required
--   CONS, EQ, NIL, NULL, QCAR, QCDR, RPLACA, RPLACD
--   Those that are included for efficiency only
--   LIST, CAR, CDR, NCONC2, NREVERSE, LENGTH
--   Also REVERSE, since it's called in Polynomial Ring

 Qfirst  ==> QCAR$Lisp
 Qrest   ==> QCDR$Lisp
 Qnull   ==> NULL$Lisp
 Qeq     ==> EQ$Lisp
 Qcons   ==> CONS$Lisp
 Qpush   ==> PUSH$Lisp
 
 Exports ==> ListAggregate S 
 Implementation ==>
  add
   #x                  == LENGTH(x)$Lisp
   concat(s:S,x:%)     == CONS(s,x)$Lisp
   eq?(x,y)            == EQ(x,y)$Lisp
   first x             == SPADfirst(x)$Lisp
   elt(x,"first")      == SPADfirst(x)$Lisp
   empty()             == NIL$Lisp
   empty? x            == NULL(x)$Lisp
   rest x              == CDR(x)$Lisp
   elt(x,"rest")       == CDR(x)$Lisp
   setfirst!(x,s)     ==
      empty? x => error "Cannot update an empty list"
      Qfirst RPLACA(x,s)$Lisp
   setelt(x,"first",s) ==
      empty? x => error "Cannot update an empty list"
      Qfirst RPLACA(x,s)$Lisp
   setrest!(x,y)      ==
      empty? x => error "Cannot update an empty list"
      Qrest RPLACD(x,y)$Lisp
   setelt(x,"rest",y)  ==
      empty? x => error "Cannot update an empty list"
      Qrest RPLACD(x,y)$Lisp
   construct l         == l pretend %
   parts s             == s pretend List S
   reverse! x         == NREVERSE(x)$Lisp
   reverse x           == REVERSE(x)$Lisp
   minIndex x          == mn

   rest(x, n) ==
      for i in 1..n repeat
         if Qnull x then error "index out of range"
         x := Qrest x
      x

   copy x ==
      y := empty()
      for i in 0.. while not Qnull x repeat
         if Qeq(i,cycleMax) and cyclic? x then error "cyclic list"
         y := Qcons(Qfirst x,y)
         x := Qrest x
      (NREVERSE(y)$Lisp)@%

   if S has CoercibleTo(OutputForm) then
     coerce(x):OutputForm ==
        -- displays cycle with overbar over the cycle
        y := empty()$List(OutputForm)
        s := cycleEntry x
        while not Qeq(x, s) repeat
          y := concat((first x)::OutputForm, y)
          x := rest x
        y := reverse! y
        empty? s => bracket y
        -- cyclic case: z is cylic part
        z := list((first x)::OutputForm)
        while not Qeq(s, rest x) repeat
           x := rest x
           z := concat((first x)::OutputForm, z)
        bracket concat!(y, overbar commaSeparate reverse! z)

   if S has SetCategory then
     x = y ==
       Qeq(x,y) => true
       while not Qnull x and not Qnull y repeat
          Qfirst x ~=$S Qfirst y => return false
          x := Qrest x
          y := Qrest y
       Qnull x and Qnull y

     latex(x : %): String ==
       s : String := "\left["
       while not Qnull x repeat
         s := concat(s, latex(Qfirst x)$S)$String
         x := Qrest x
         if not Qnull x then s := concat(s, ", ")$String
       concat(s, " \right]")$String

     member?(s,x) ==
        while not Qnull x repeat
           if s = Qfirst x then return true else x := Qrest x
        false

   -- Lots of code from parts of AGGCAT, repeated here to
   -- get faster compilation
   concat!(x:%,y:%) ==
      Qnull x => 
        Qnull y => x
        Qpush(first y,x)
        QRPLACD(x,rest y)$Lisp
        x
      z:=x
      while not Qnull Qrest z repeat
        z:=Qrest z
      QRPLACD(z,y)$Lisp
      x

   -- Then a quicky:
   if S has SetCategory then
     removeDuplicates! l ==
       p := l
       while not Qnull p repeat
--       p := setrest!(p, remove!(#1 = Qfirst p, Qrest p))
-- far too expensive - builds closures etc.
         pp:=p
         f:S:=Qfirst p
         p:=Qrest p
         while not Qnull (pr:=Qrest pp) repeat
           if (Qfirst pr)@S = f then QRPLACD(pp,Qrest pr)$Lisp
           else pp:=pr
       l

   -- then sorting
   mergeSort: ((S, S) -> Boolean, %, Integer) -> %

   sort!(f, l)       == mergeSort(f, l, #l)

   merge!(f, p, q) ==
     Qnull p => q
     Qnull q => p
     Qeq(p, q) => error "cannot merge a list into itself"
     if f(Qfirst p, Qfirst q)
       then (r := t := p; p := Qrest p)
       else (r := t := q; q := Qrest q)
     while not Qnull p and not Qnull q repeat
       if f(Qfirst p, Qfirst q)
         then (QRPLACD(t, p)$Lisp; t := p; p := Qrest p)
         else (QRPLACD(t, q)$Lisp; t := q; q := Qrest q)
     QRPLACD(t, if Qnull p then q else p)$Lisp
     r

   split!(p, n) ==
      n < 1 => error "index out of range"
      p := rest(p, (n - 1)::NonNegativeInteger)
      q := Qrest p
      QRPLACD(p, NIL$Lisp)$Lisp
      q

   mergeSort(f, p, n) ==
     if n = 2 and f(first rest p, first p) then p := reverse! p
     n < 3 => p
     l := (n quo 2)::NonNegativeInteger
     q := split!(p, l)
     p := mergeSort(f, p, l)
     q := mergeSort(f, q, n - l)
     merge!(f, p, q)

@

\section{domain LIST List}
<<domain LIST List>>=
import Type
import ListAggregate
)abbrev domain LIST List
++ Author: Michael Monagan
++ Date Created: Sep 1987
++ Change History:
++ Basic Operations:
++   \#, append, concat, concat!, cons, construct, copy, elt, elt,
++   empty, empty?, eq?, first, member?, merge!, mergeSort, minIndex,
++   nil, null, parts, removeDuplicates!, rest, rest, reverse,
++   reverse!, setDifference, setIntersection, setUnion, setelt,
++   setfirst!, setrest!, sort!, split!
++ Related Constructors: ListFunctions2, ListFunctions3, ListToMap
++ Also See: IndexList, ListAggregate
++ AMS Classification:
++ Keywords: list, index, aggregate, lisp
++ Description:
++   \spadtype{List} implements singly-linked lists that are
++   addressable by indices; the index of the first element
++   is 1. In addition to the operations provided by
++   \spadtype{IndexedList}, this constructor provides some
++   LISP-like functions such as \spadfun{null} and \spadfun{cons}.
List(S:Type): Exports == Implementation where 
 LISTMININDEX ==> 1       -- this is the minimum list index

 Exports ==> ListAggregate S with
  nil             : %
    ++ \spad{nil} is the empty list.
  null            : %      -> Boolean
    ++ null(u) tests if list \spad{u} is the
    ++ empty list.
  cons            : (S, %) -> %
    ++ cons(element,u) appends \spad{element} onto the front
    ++ of list \spad{u} and returns the new list. This new list
    ++ and the old one will share some structure.
  append          : (%, %) -> %
    ++ append(u1,u2) appends the elements of list \spad{u1}
    ++ onto the front of list \spad{u2}. This new list
    ++ and \spad{u2} will share some structure.
  if S has SetCategory then
    setUnion        : (%, %) -> %
      ++ setUnion(u1,u2) appends the two lists u1 and u2, then
      ++ removes all duplicates. The order of elements in the
      ++ resulting list is unspecified.
    setIntersection : (%, %) -> %
      ++ setIntersection(u1,u2) returns a list of the elements
      ++ that lists \spad{u1} and \spad{u2} have in common.
      ++ The order of elements in the resulting list is unspecified.
    setDifference   : (%, %) -> %
      ++ setDifference(u1,u2) returns a list of the elements
      ++ of \spad{u1} that are not also in \spad{u2}.
      ++ The order of elements in the resulting list is unspecified.
  if S has OpenMath then OpenMath

 Implementation ==>
   IndexedList(S, LISTMININDEX) add
      nil                      == NIL$Lisp
      null l                   == NULL(l)$Lisp
      cons(s, l)               == CONS(s, l)$Lisp
      append(l:%, t:%)         == APPEND(l, t)$Lisp

      if S has OpenMath then
        writeOMList(dev: OpenMathDevice, x: %): Void ==
          OMputApp(dev)
          OMputSymbol(dev, "list1", "list")
          -- The following didn't compile because the compiler isn't
          -- convinced that `xval' is a S.  Duhhh! MCD.
          --for xval in x repeat
          --  OMwrite(dev, xval, false)
          while not null x repeat
            OMwrite(dev,first x,false)
            x := rest x
          OMputEndApp(dev)

        OMwrite(x: %): String ==
          s: String := ""
          sp := OM_-STRINGTOSTRINGPTR(s)$Lisp
          dev: OpenMathDevice := OMopenString(sp pretend String, OMencodingXML)
          OMputObject(dev)
          writeOMList(dev, x)
          OMputEndObject(dev)
          OMclose(dev)
          s := OM_-STRINGPTRTOSTRING(sp)$Lisp pretend String
          s

        OMwrite(x: %, wholeObj: Boolean): String ==
          s: String := ""
          sp := OM_-STRINGTOSTRINGPTR(s)$Lisp
          dev: OpenMathDevice := OMopenString(sp pretend String, OMencodingXML)
          if wholeObj then
            OMputObject(dev)
          writeOMList(dev, x)
          if wholeObj then
            OMputEndObject(dev)
          OMclose(dev)
          s := OM_-STRINGPTRTOSTRING(sp)$Lisp pretend String
          s

        OMwrite(dev: OpenMathDevice, x: %): Void ==
          OMputObject(dev)
          writeOMList(dev, x)
          OMputEndObject(dev)

        OMwrite(dev: OpenMathDevice, x: %, wholeObj: Boolean): Void ==
          if wholeObj then
            OMputObject(dev)
          writeOMList(dev, x)
          if wholeObj then
            OMputEndObject(dev)

      if S has SetCategory then
        setUnion(l1:%,l2:%)      == removeDuplicates concat(l1,l2)

        setIntersection(l1:%,l2:%) ==
          u :% := empty()
          l1 := removeDuplicates l1
          while not empty? l1 repeat
            if member?(first l1,l2) then u := cons(first l1,u)
            l1 := rest l1
          u

        setDifference(l1:%,l2:%) ==
          l1 := removeDuplicates l1
          lu:% := empty()
          while not empty? l1 repeat
            l11:=l1.1
            if not member?(l11,l2) then lu := concat(l11,lu)
            l1 := rest l1
          lu

      if S has ConvertibleTo InputForm then
        convert(x:%):InputForm ==
          convert concat(convert('construct)@InputForm,
                [convert a for a in (x pretend List S)]$List(InputForm))

@

\section{package LIST2 ListFunctions2}

<<package LIST2 ListFunctions2>>=
import Type
import FiniteLinearAggregateFunctions2
)abbrev package LIST2 ListFunctions2
++ Author:
++ Date Created:
++ Change History:
++ Basic Operations: map, reduce, scan
++ Related Constructors: List
++ Also See: ListFunctions3
++ AMS Classification:
++ Keywords: list, aggregate, map, reduce
++ Description:
++   \spadtype{ListFunctions2} implements utility functions that
++   operate on two kinds of lists, each with a possibly different
++   type of element.
ListFunctions2(A:Type, B:Type): public == private where
  LA     ==> List A
  LB     ==> List B
  O2     ==> FiniteLinearAggregateFunctions2(A, LA, B, LB)

  public ==> with
    scan:    ((A, B) -> B, LA, B) -> LB
      ++ scan(fn,u,ident) successively uses the binary function
      ++ \spad{fn} to reduce more and more of list \spad{u}.
      ++ \spad{ident} is returned if the \spad{u} is empty.
      ++ The result is a list of the reductions at each step. See
      ++ \spadfun{reduce} for more information. Examples:
      ++ \spad{scan(fn,[1,2],0) = [fn(2,fn(1,0)),fn(1,0)]} and
      ++ \spad{scan(*,[2,3],1) = [2 * 1, 3 * (2 * 1)]}.
    reduce:  ((A, B) -> B, LA, B) -> B
      ++ reduce(fn,u,ident) successively uses the binary function
      ++ \spad{fn} on the elements of list \spad{u} and the result
      ++ of previous applications. \spad{ident} is returned if the
      ++ \spad{u} is empty. Note the order of application in
      ++ the following examples:
      ++ \spad{reduce(fn,[1,2,3],0) = fn(3,fn(2,fn(1,0)))} and
      ++ \spad{reduce(*,[2,3],1) = 3 * (2 * 1)}.
    map:      (A -> B, LA) -> LB
      ++ map(fn,u) applies \spad{fn} to each element of
      ++ list \spad{u} and returns a new list with the results.
      ++ For example \spad{map(square,[1,2,3]) = [1,4,9]}.

  private ==> add
    map(f, l)       == map(f, l)$O2
    scan(f, l, b)   == scan(f, l, b)$O2
    reduce(f, l, b) == reduce(f, l, b)$O2

@

\section{package LIST3 ListFunctions3}

<<package LIST3 ListFunctions3>>=
import Type
import Type
)abbrev package LIST3 ListFunctions3
++ Author:
++ Date Created:
++ Change History:
++ Basic Operations: map
++ Related Constructors: List
++ Also See: ListFunctions2
++ AMS Classification:
++ Keywords: list, aggregate, map
++ Description:
++   \spadtype{ListFunctions3} implements utility functions that
++   operate on three kinds of lists, each with a possibly different
++   type of element.
ListFunctions3(A:Type, B:Type, C:Type): public == private where
  LA     ==> List A
  LB     ==> List B
  LC     ==> List C

  public ==> with
    map: ( (A,B)->C, LA, LB) -> LC
      ++ map(fn,list1, u2) applies the binary function \spad{fn}
      ++ to corresponding elements of lists \spad{u1} and \spad{u2}
      ++ and returns a list of the results (in the same order). Thus
      ++ \spad{map(/,[1,2,3],[4,5,6]) = [1/4,2/4,1/2]}. The computation
      ++ terminates when the end of either list is reached. That is,
      ++ the length of the result list is equal to the minimum of the
      ++ lengths of \spad{u1} and \spad{u2}.

  private ==> add
    map(fn : (A,B) -> C, la : LA, lb : LB): LC ==
      empty?(la) or empty?(lb) => empty()$LC
      concat(fn(first la, first lb), map(fn, rest la, rest lb))

@

\section{package LIST2MAP ListToMap}

<<package LIST2MAP ListToMap>>=
import Type
import SetCategory
import List
)abbrev package LIST2MAP ListToMap
++ Author: Manuel Bronstein
++ Date Created: 22 Mar 1988
++ Change History:
++   11 Oct 1989   MB   ?
++ Basic Operations: match
++ Related Constructors: List
++ Also See:
++ AMS Classification:
++ Keywords: mapping, list
++ Description:
++   \spadtype{ListToMap} allows mappings to be described by a pair of
++   lists of equal lengths.  The image of an element \spad{x},
++   which appears in position \spad{n} in the first list, is then
++   the \spad{n}th element of the second list.  A default value or
++   default function can be specified to be used when \spad{x}
++   does not appear in the first list.  In the absence of defaults,
++   an error will occur in that case.
ListToMap(A:SetCategory, B:Type): Exports == Implementation where
  LA  ==> List A
  LB  ==> List B
  AB  ==> (A -> B)

  Exports ==> with
    match: (LA, LB   ) -> AB
      ++ match(la, lb) creates a map with no default source or target values
      ++ defined by lists la and lb of equal length.
      ++ The target of a source value \spad{x} in la is the
      ++ value y with the same index lb.
      ++ Error: if la and lb are not of equal length.
      ++ Note: when this map is applied, an error occurs when
      ++ applied to a value missing from la.
    match: (LA, LB, A) -> B
      ++ match(la, lb, a) creates a map
      ++ defined by lists la and lb of equal length, where \spad{a} is used
      ++ as the default source value if the given one is not in \spad{la}.
      ++ The target of a source value \spad{x} in la is the
      ++ value y with the same index lb.
      ++ Error: if la and lb are not of equal length.
    match: (LA, LB, B)    -> AB
      ++ match(la, lb, b) creates a map
      ++ defined by lists la and lb of equal length, where \spad{b} is used
      ++ as the default target value if the given function argument is
      ++ not in \spad{la}.
      ++ The target of a source value \spad{x} in la is the
      ++ value y with the same index lb.
      ++ Error: if la and lb are not of equal length.
    match: (LA, LB, A, B) -> B
      ++ match(la, lb, a, b) creates a map
      ++ defined by lists la and lb of equal length.
      ++ and applies this map to a.
      ++ The target of a source value \spad{x} in la is the
      ++ value y with the same index lb.
      ++ Argument b is the default target value if a is not in la.
      ++ Error: if la and lb are not of equal length.
    match: (LA, LB, AB)    -> AB
      ++ match(la, lb, f) creates a map
      ++ defined by lists la and lb of equal length.
      ++ The target of a source value \spad{x} in la is the
      ++ value y with the same index lb.
      ++ Argument \spad{f} is used as the
      ++ function to call when the given function argument is not in
      ++ \spad{la}.
      ++ The value returned is f applied to that argument.
    match: (LA, LB, A, AB) -> B
      ++ match(la, lb, a, f) creates a map
      ++ defined by lists la and lb of equal length.
      ++ and applies this map to a.
      ++ The target of a source value \spad{x} in la is the
      ++ value y with the same index lb.
      ++ Argument \spad{f} is a default function to call if a is not in la.
      ++ The value returned is then obtained by applying f to argument a.

  Implementation ==> add
    match(la, lb)             == match(la, lb, #1)
    match(la:LA, lb:LB, a:A)  == lb.position(a, la)
    match(la:LA, lb:LB, b:B)  == match(la, lb, #1, b)
    match(la:LA, lb:LB, f:AB) == match(la, lb, #1, f)

    match(la:LA, lb:LB, a:A, b:B) ==
      (p := position(a, la)) < minIndex(la) => b
      lb.p

    match(la:LA, lb:LB, a:A, f:AB) ==
      (p := position(a, la)) < minIndex(la) => f a
      lb.p

@

\section{domain ALIST AssociationList}

<<domain ALIST AssociationList>>=
import SetCategory
import List
import Reference
)abbrev domain ALIST AssociationList
++ Author:
++ Date Created:
++ Change History:
++ Basic Operations: empty, empty?, keys, \#, concat, first, rest,
++   setrest!, search, setelt, remove!
++ Related Constructors:
++ Also See: List
++ AMS Classification:
++ Keywords: list, association list
++ Description:
++   \spadtype{AssociationList} implements association lists. These
++   may be viewed as lists of pairs where the first part is a key
++   and the second is the stored value. For example, the key might
++   be a string with a persons employee identification number and
++   the value might be a record with personnel data.

AssociationList(Key:SetCategory, Entry:SetCategory):
 AssociationListAggregate(Key, Entry) == add
        Pair ==> Record(key:Key, entry:Entry)
        Rep := Reference List Pair

        dictionary()            == ref empty()
        empty()                 == dictionary()
        empty? t                == empty? deref t
        entries(t:%):List(Pair) == deref t
        parts(t:%):List(Pair)   == deref t
        keys t                  == [k.key for k in deref t]
        # t                     == # deref t
        first(t:%):Pair         == first deref t
        rest t                  == ref rest deref t
        concat(p:Pair, t:%)     == ref concat(p, deref t)
        setrest!(a:%, b:%)     == ref setrest!(deref a, deref b)
        setfirst!(a:%, p:Pair) == setfirst!(deref a,p)
        minIndex(a:%):Integer   == minIndex(deref a)
        maxIndex(a:%):Integer   == maxIndex(deref a)

        search(k, t) ==
          for r in deref t repeat
            k = r.key => return(r.entry)
          "failed"

        latex(a : %) : String ==
          l : List Pair := entries a
          s : String := "\left["
          while not empty?(l) repeat
            r : Pair := first l
            l        := rest l
            s := concat(s, concat(latex r.key, concat(" = ", latex r.entry)$String)$String)$String
            if not empty?(l) then s := concat(s, ", ")$String
          concat(s, " \right]")$String

--      assoc(k, l) ==
--        (r := find(#1.key=k, l)) case "failed" => "failed"
--        r

        assoc(k, t) ==
          for r in deref t repeat
            k = r.key => return r
          "failed"

        setelt(t:%, k:Key, e:Entry) ==
          (r := assoc(k, t)) case Pair => (r::Pair).entry := e
          setref(t, concat([k, e], deref t))
          e

        remove!(k:Key, t:%) ==
          empty?(l := deref t) => "failed"
          k = first(l).key =>
            setref(t, rest l)
            first(l).entry
          prev := l
          curr := rest l
          while not empty? curr and first(curr).key ~= k repeat
            prev := curr
            curr := rest curr
          empty? curr => "failed"
          setrest!(prev, rest curr)
          first(curr).entry

@

\section{License}

<<license>>=
--Copyright (c) 1991-2002, The Numerical ALgorithms Group Ltd.
--All rights reserved.
--Copyright (C) 2007-2009, 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>>

<<domain ILIST IndexedList>>
<<domain LIST List>>
<<package LIST2 ListFunctions2>>
<<package LIST3 ListFunctions3>>
<<package LIST2MAP ListToMap>>
<<domain ALIST AssociationList>>
@
\eject
\begin{thebibliography}{99}
\bibitem{1} nothing
\end{thebibliography}
\end{document}