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2.4.5 Floating point literals

Floating point literals are described by the following lexical definitions:

floatnumber pointfloat | exponentfloat

pointfloat [ intpart ] fraction | intpart "."

exponentfloat ( intpart | pointfloat ) exponent

intpart digit+

fraction "." digit+

exponent ( "e" | "E" ) [ "+" | "-" ] digit+

Note that the integer and exponent parts of floating point numbers can look like octal integers, but are interpreted using radix 10. For example, ‘077e010’ is legal, and denotes the same number as ‘77e10’. The allowed range of floating point literals is implementation-dependent. Some examples of floating point literals:

    3.14    10.    .001    1e100    3.14e-10    0e0

Note that floating-point literals do not include a sign; a phrase like -1.0 is actually an expression composed of the unary operator - and the literal 1.0.