Numeric Literals (Summary 2)

--- Numeric Literals ---

decimal notation:
      123       # int 123
     0123       # int 123
     123.0      # num 123.0
     -123       # int -123

    0_1.2_3     # ok
    _01.23      # wrong
    01.23_      # wrong
    01_._23     # wrong
    1__2        # wrong

exponential notation:
    -1.23e4     # num
    -1.23E4     # num (identical)
    1.23_e_4    # wrong

bin/oct/hex notation:

    0b0110      # bin
    0c0123      # oct
    0x00ff      # hex
    0x00fF      # hex, == 0x00ff
    0x00FF      # hex, == 0x00ff

    -0xff       # ok
    -0x00ff     # ok

    0xf_f       # ok
    0x_ff       # ok

explicit radix:

    (radix 2-32)

    20:1gj       # base 20
    20:1GJ       # base 20 (identical)
    20:1.G.J     # base 20 (identical)
    20:1_G_J     # base 20 (identical)
    20:1.16.19   # base 20 (identical)
    20:1_16_19   # NOT identical; == 20:11619
    20:1.1_6.19  # WRONG: dotted form may not have underlines

    -20:1GJ      # base 20 (negative)
    -20:1.16.19  # base 20 (negative)

    62:zZ       # base 62 (?)
    62:z.Z      # base 62 (identical?)
    62:z_Z      # base 62 (identical?)
    62:Zz       # base 62 (not identical?)

   (radix 33-RADIX_MAX)

   256:0.253.254.255   # base 256
   256:0_253_254_255   # base 256


Other issues w/ literals:

- radix <= 32, alpha digits may be upper or lowercase
- underlines may appear ONLY between digits
- dotted form may therefore not have underlines
- radix < 2 throws error
- negative sign goes before radix, e.g. -20:1GJ, in
    order to match usage in cases like -0x00ff.
- need to specify RADIX_MAX

- can't have runtime radix, e.g. 2**8:10, because : binds
    tighter.  can't say (2**8):10, because not a literal
    anymore, and ':' is used for adverbial in many locations
    (ambiguous).

- need to verify that 0b1, 0c1, 0x1 are still allowed in addition to 
explicit radix (but seems appropriate to leave them in, given their 
frequency.)

MikeL