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### 6.2.4 Syntax of numerical constants

The syntax of the written representations for numbers is described formally in section Lexical structure. Note that case is not significant in numerical constants.

A number may be written in binary, octal, decimal, or
hexadecimal by the use of a radix prefix. The radix prefixes are ‘`#b`’ (binary), ‘`#o`’ (octal), ‘`#d`’ (decimal), and ‘`#x`’ (hexadecimal). With
no radix prefix, a number is assumed to be expressed in decimal.

A
numerical constant may be specified to be either exact or
inexact by a prefix. The prefixes are ‘`#e`’
for exact, and ‘`#i`’ for inexact. An exactness
prefix may appear before or after any radix prefix that is used. If
the written representation of a number has no exactness prefix, the
constant may be either inexact or exact. It is
inexact if it contains a decimal point, an
exponent, or a “#” character in the place of a digit,
otherwise it is exact.

In systems with inexact numbers
of varying precisions it may be useful to specify
the precision of a constant. For this purpose, numerical constants
may be written with an exponent marker that indicates the
desired precision of the inexact
representation. The letters ‘`s`’, ‘`f`’,
‘`d`’, and ‘`l`’ specify the use of `short`, `single`,
`double`, and `long` precision, respectively. (When fewer
than four internal
inexact
representations exist, the four size
specifications are mapped onto those available. For example, an
implementation with two internal representations may map short and
single together and long and double together.) In addition, the
exponent marker ‘`e`’ specifies the default precision for the
implementation. The default precision has at least as much precision
as `double`, but
implementations may wish to allow this default to be set by the user.

3.14159265358979F0 Round to single --- 3.141593 0.6L0 Extend to long --- .600000000000000

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