[GHC] #16403: Add isBinDigit to Data.Char

[GHC]

#16403: Add isBinDigit to Data.Char
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           Reporter:  hesiod         |             Owner:  (none)
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:
          Component:                 |           Version:  8.6.4
  libraries/base                     |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 The {{{Data.Char}}} module contains helper functions that determine
 whether a Char is a decimal, octal or hexadecimal digit ({{{isDigit}}},
 {{{isOctDigit}}}, {{{isHexDigit}}}). A similar helper function for binary
 digits is not included for no apparent reason (maybe because the number
 parsers in the {{{Numeric}}} module also don't support binary digits?).

 The implementation for such a {{{isBinDigit}}} should be trivial, aside
 from performance considerations: {{{isDigit}}} and friends perform the
 test using only subtraction and an unsigned comparison, I'm not sure
 whether {{{isBinDigit}}} offers any different performant implementations.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16403>
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