1 [ {literal (based)} {binary literal} {base 2 literal} {binary (literal)} {octal literal} {base 8 literal} {octal (literal)} {hexadecimal literal} {base 16 literal} {hexadecimal (literal)} A based_literal is a numeric_literal expressed in a form that specifies the base explicitly.]
2 based_literal ::= base # based_numeral [.based_numeral] # [exponent]
3 base ::= numeral
4 based_numeral ::= extended_digit {[underline] extended_digit}
5 extended_digit ::= digit | A | B | C | D | E | F
6 {base} The base (the numeric value of the decimal numeral preceding the first #) shall be at least two and at most sixteen. The extended_digits A through F represent the digits ten through fifteen, respectively. The value of each extended_digit of a based_literal shall be less than the base.
7 The conventional meaning of based notation is assumed. An exponent indicates the power of the base by which the value of the based_literal without the exponent is to be multiplied to obtain the value of the based_literal with the exponent. The base and the exponent, if any, are in decimal notation.
8 The extended_digits A through F can be written either in lower case or in upper case, with the same meaning.
9 Examples of based literals:
10
2#1111_1111# 16#FF# 016#0ff# -- integer literals of value 255 16#E#E1 2#1110_0000# -- integer literals of value 224 16#F.FF#E+2 2#1.1111_1111_1110#E11 -- real literals of value 4095.0
10.a The rule about which letters are allowed is now encoded in BNF, as suggested by Mike Woodger. This is clearly more readable.
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With the use of a pragma, the user may authorize bases 2 to 36. Bases higher than 10 use the ASCII letters A to Z as required. The letter A represents 10, B represents 11, etc. up to Z that represents 35. The corresponding lowercase characters (a to z) represent the same values.
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