[GHC] #9224: Add support for binary integer literals

[GHC]

#9224: Add support for binary integer literals
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        Reporter:  hvr               |            Owner:
            Type:  feature request   |           Status:  new
        Priority:  normal            |        Milestone:  7.10.1
       Component:  Compiler          |          Version:
  (Parser)                           |         Keywords:  literals
      Resolution:                    |     Architecture:  Unknown/Multiple
Operating System:  Unknown/Multiple  |       Difficulty:  Easy (less than 1
 Type of failure:  None/Unknown      |  hour)
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Description changed by hvr:

Old description:

> Currently, Haskell98/2010 support base-10, base-8 (via `0[oO]`-prefix)
> and base-16 (via `0[xX]`-prefix) integer literals.
>
> I hereby propose to add conditional support for base-2 integers via a
> `0[bB]`-prefix, controlled via a new `-XBinaryLiterals` language
> extension flag/pragma. The change to the lexer is trivial (see attached
> patch), however I'm stuck on the lexer using a 32-bit feature-mask, of
> which all 32bits are already taken, and I'd need a 33th bit for the
> `BinaryLiteralsBit` flag.

New description:

 Haskell2010 supports

 - base-10 (prefix-less),
 - base-8 (via `0[oO]`-prefix), and
 - base-16 (via `0[xX]`-prefix) integer literals.

 I hereby propose to add conditional support for base-2 integers literals
 via a `0[bB]`-prefix, disabled by default, and controllable via a new `{-#
 LANGUAGE BinaryLiterals #-}` language extension flag/pragma.

 The use of a `0b` prefix for indicating binary literals is known
 from popular programming languages such as Python, Ruby, and Java.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9224#comment:2>
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