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floating point literal

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Floating point literal defines a compile-time constant whose value is specified in the source file.

Syntax

A floating-point literals have two syntaxes. The first one consists of the following parts:

  • nonempty sequence of decimal digits containing a decimal point character (defines significand)
  • (optional) e or E followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent)
  • (optional) a suffix type specifier as a l, f, L or F

The second one consists of the following parts:

  • nonempty sequence of decimal digits (defines significant)
  • e or E followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent)
  • (optional) a suffix type specifier as a l, f, L or F

The suffix type specifier defines the actual type of the floating-point literal:

  • (no suffix) defines double
  • f F defines float
  • l L defines long double

Explanation

A decimal scientific notation is used, meaning that the exponent is the power of 10 by which the significant is multiplied.
The mathematical meaning of 123e4 is 123×104

Example

std::cout << 123.456e-67 << '\n'
          << .1E4f       << '\n'
          << 58.         << '\n'
          << 4e2         << '\n';

Output:

1.23456e-65
1000
58
400