)abbrev domain SET Set
++ Author: Michael Monagan; revised by Richard Jenks
++ Date Created: August 87 through August 88
++ Basic Operations:
++ Related Constructors:
++ Also See:
++ AMS Classifications:
++ Keywords:
++ References:
++ Description:
++ A set over a domain S models the usual mathematical notion of a finite set
++ of elements from S.
++ Sets are unordered collections of distinct elements
++ (that is, order and duplication does not matter).
++ The notation \spad{set [a, b, c]} can be used to create
++ a set and the usual operations such as union and intersection are available
++ to form new sets.
++ If S has OrderdSet, \Language{} maintains the entries in
++ sorted order.  Specifically, the parts function returns the entries
++ as a list in ascending order and
++ the \spadfun{extract!} operation returns the maximum entry.
++ Given two sets s and t where \spad{#s = m} and \spad{#t = n},
++ the complexity of
++   \spad{s = t} is \spad{O(min(n, m))}
++   \spad{s < t} is \spad{O(max(n, m))}
++   \spad{union(s, t)}, \spad{intersect(s, t)}, \spad{minus(s, t)}, \spad{symmetricDifference(s, t)} is \spad{O(max(n, m))}
++   \spad{member?(x, t)} is \spad{O(n log n)}
++   \spad{insert!(x, t)} and \spad{remove!(x, t)} is \spad{O(n)}
Set(S : SetCategory) : FiniteSetAggregate S == add
   Rep := FlexibleArray(S)
   # s       == _#$Rep s
   set()     == empty()
   empty()   == empty()$Rep
   copy s    == copy(s)$Rep
   parts s   == parts(s)$Rep
   inspect s == (empty? s => error "Empty set"; s(maxIndex s))

   extract! s ==
     x := inspect s
     delete!(s, maxIndex s)
     x

   find(f, s) == find(f, s)$Rep

   map(f, s) == map!(f, copy s)

   reduce(f, s) == reduce(f, s)$Rep

   reduce(f, s, x) == reduce(f, s, x)$Rep

   reduce(f, s, x, y) == reduce(f, s, x, y)$Rep

   if S has ConvertibleTo InputForm then
     convert(x : %) : InputForm ==
        convert [convert('set)@InputForm,
                          convert(parts x)@InputForm]

   if S has OrderedSet then
     s = t == s =$Rep t
     max s == inspect s
     min s == (empty? s => error "Empty set"; s(minIndex s))

     map!(f, s) ==
        map!(f, s)$Rep
        sort!(s)$Rep
        removeRepeats! s

     construct l ==
       zero?(n := #l) => empty()
       a := new(n, first l)
       for i in minIndex(a).. for x in l repeat a.i := x
       removeRepeats! sort! a

     insert!(x, s) ==
       n := inc maxIndex s
       k := minIndex s
       while k < n and x > s.k repeat k := inc k
       k < n and s.k = x => s
       insert!(x, s, k)

     member?(x, s) == -- binary search
       empty? s => false
       t := maxIndex s
       b := minIndex s
       while b < t repeat
         m := (b+t) quo 2
         if x > s.m then b := m+1 else t := m
       x = s.t

     remove!(x : S, s : %) ==
       n := inc maxIndex s
       k := minIndex s
       while k < n and x > s.k repeat k := inc k
       k < n and x = s.k => delete!(s, k)
       s

     -- the set operations are implemented as variations of merging
     intersect(s, t) ==
       m := maxIndex s
       n := maxIndex t
       i := minIndex s
       j := minIndex t
       r := empty()
       while i <= m and j <= n repeat
         s.i = t.j => (concat!(r, s.i); i := i+1; j := j+1)
         if s.i < t.j then i := i+1 else j := j+1
       r

     difference(s : %, t : %) ==
       m := maxIndex s
       n := maxIndex t
       i := minIndex s
       j := minIndex t
       r := empty()
       while i <= m and j <= n repeat
         s.i = t.j => (i := i+1; j := j+1)
         s.i < t.j => (concat!(r, s.i); i := i+1)
         j := j+1
       while i <= m repeat (concat!(r, s.i); i := i+1)
       r

     symmetricDifference(s, t) ==
       m := maxIndex s
       n := maxIndex t
       i := minIndex s
       j := minIndex t
       r := empty()
       while i <= m and j <= n repeat
         s.i < t.j => (concat!(r, s.i); i := i+1)
         s.i > t.j => (concat!(r, t.j); j := j+1)
         i := i+1; j := j+1
       while i <= m repeat (concat!(r, s.i); i := i+1)
       while j <= n repeat (concat!(r, t.j); j := j+1)
       r

     subset?(s, t) ==
       m := maxIndex s
       n := maxIndex t
       m > n => false
       i := minIndex s
       j := minIndex t
       while i <= m and j <= n repeat
         s.i = t.j => (i := i+1; j := j+1)
         s.i > t.j => j := j+1
         return false
       i > m

     union(s : %, t : %) ==
       m := maxIndex s
       n := maxIndex t
       i := minIndex s
       j := minIndex t
       r := empty()
       while i <= m and j <= n repeat
         s.i = t.j => (concat!(r, s.i); i := i+1; j := j+1)
         s.i < t.j => (concat!(r, s.i); i := i+1)
         (concat!(r, t.j); j := j+1)
       while i <= m repeat (concat!(r, s.i); i := i+1)
       while j <= n repeat (concat!(r, t.j); j := j+1)
       r

    else
      insert!(x, s) ==
        for k in minIndex s .. maxIndex s repeat
          s.k = x => return s
        insert!(x, s, inc maxIndex s)

      remove!(x : S, s : %) ==
        n := inc maxIndex s
        k := minIndex s
        while k < n repeat
          x = s.k => return delete!(s, k)
          k := inc k
        s

      map!(f, s) ==
        map!(f, s)$Rep
        removeDuplicates! s

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