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Decimal Expansion
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All rationals have repeating decimal expansions.  Operations to access
the individual digits of a decimal expansion can be obtained by
converting the value to ``RadixExpansion(10)``.  

The operation decimal is used to create this expansion of type
DecimalExpansion. ::

  r := decimal(22/7)
      ______
    3.142857
                      Type: DecimalExpansion

Arithmetic is exact. ::

  r + decimal(6/7)
   4
                      Type: DecimalExpansion

The period of the expansion can be short or long ... ::

  [decimal(1/i) for i in 350..354]
        ______    ______         __    ________________________________
   [0.00285714, 0.002849, 0.0028409, 0.00283286118980169971671388101983,
       __________________________________________________________
    0.00282485875706214689265536723163841807909604519774011299435]
                      Type: List DecimalExpansion

or very long. ::

  decimal(1/2049)
     _______________________________________________________________________
   0.00048804294777940458760370912640312347486578818936066373840897999023914
     _____________________________________________________________________
     104441190824792581747193753050268423621278672523182040019521717911176
     _____________________________________________________________________
     183504148365056124938994631527574426549536359199609565641776476329917
     _____________________________________________________________________
     032698877501220107369448511469009272816007808687164470473401659346022
     _______________________________________________________________
     449975597852611029770619814543679843826256710590531966813079551
                     Type: DecimalExpansion

These numbers are bona fide algebraic objects. ::

  p := decimal(1/4)*x**2 + decimal(2/3)*x + decimal(4/9) 
        2     _      _
   0.25x  + 0.6x + 0.4
                     Type: Polynomial DecimalExpansion

  q := differentiate(p, x)
            _
   0.5x + 0.6
                     Type: Polynomial DecimalExpansion

  g := gcd(p, q)
         _
   x + 1.3
                     Type: Polynomial DecimalExpansion

See Also:

* ``)help RadixExpansion``
* ``)help BinaryExpansion``
* ``)help HexadecimalExpansion``
* ``)show DecimalExpansion``