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Universal Segment
====================================================================

The UniversalSegment domain generalizes Segment by allowing segments
without a "hi" end point. ::

  pints := 1..
    1..
                                Type: UniversalSegment PositiveInteger

  nevens := (0..) by -2
    0.. by - 2
                                Type: UniversalSegment NonNegativeInteger

Values of type Segment are automatically converted to type
UniversalSegment when appropriate. ::

  useg: UniversalSegment(Integer) := 3..10
    3..10
                                Type: UniversalSegment Integer

The operation hasHi is used to test whether a segment has a hi end point. ::

  hasHi pints
    false
                                Type: Boolean

  hasHi nevens
    false
                                Type: Boolean

  hasHi useg
    true
                                Type: Boolean

All operations available on type Segment apply to UniversalSegment, with 
the proviso that expansions produce streams rather than lists.  This is 
to accommodate infinite expansions. ::

  expand pints
    [1,2,3,4,5,6,7,8,9,10,...]
                                Type: Stream Integer

  expand nevens
    [0,- 2,- 4,- 6,- 8,- 10,- 12,- 14,- 16,- 18,...]
                                Type: Stream Integer

  expand [1, 3, 10..15, 100..]
    [1,3,10,11,12,13,14,15,100,101,...]
                                Type: Stream Integer

See Also:

* )help Segment
* )help SegmentBinding
* )help List
* )help Stream
* )show UniversalSegment