(octave.info)Floating-Point Conversions

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14.2.9 Floating-Point Conversions
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This section discusses the conversion specifications for floating-point
numbers: the ‘%f’, ‘%e’, ‘%E’, ‘%g’, and ‘%G’ conversions.

   The ‘%f’ conversion prints its argument in fixed-point notation,
producing output of the form [‘-’]DDD‘.’DDD, where the number of digits
following the decimal point is controlled by the precision you specify.

   The ‘%e’ conversion prints its argument in exponential notation,
producing output of the form [‘-’]D‘.’DDD‘e’[‘+’|‘-’]DD.  Again, the
number of digits following the decimal point is controlled by the
precision.  The exponent always contains at least two digits.  The ‘%E’
conversion is similar but the exponent is marked with the letter ‘E’
instead of ‘e’.

   The ‘%g’ and ‘%G’ conversions print the argument in the style of ‘%e’
or ‘%E’ (respectively) if the exponent would be less than -4 or greater
than or equal to the precision; otherwise they use the ‘%f’ style.
Trailing zeros are removed from the fractional portion of the result and
a decimal-point character appears only if it is followed by a digit.

   The following flags can be used to modify the behavior:

‘-’
     Left-justify the result in the field.  Normally the result is
     right-justified.

‘+’
     Always include a plus or minus sign in the result.

‘ ’
     If the result doesn’t start with a plus or minus sign, prefix it
     with a space instead.  Since the ‘+’ flag ensures that the result
     includes a sign, this flag is ignored if you supply both of them.

‘#’
     Specifies that the result should always include a decimal point,
     even if no digits follow it.  For the ‘%g’ and ‘%G’ conversions,
     this also forces trailing zeros after the decimal point to be left
     in place where they would otherwise be removed.

‘0’
     Pad the field with zeros instead of spaces; the zeros are placed
     after any sign.  This flag is ignored if the ‘-’ flag is also
     specified.

   The precision specifies how many digits follow the decimal-point
character for the ‘%f’, ‘%e’, and ‘%E’ conversions.  For these
conversions, the default precision is ‘6’.  If the precision is
explicitly ‘0’, this suppresses the decimal point character entirely.
For the ‘%g’ and ‘%G’ conversions, the precision specifies how many
significant digits to print.  Significant digits are the first digit
before the decimal point, and all the digits after it.  If the precision
is ‘0’ or not specified for ‘%g’ or ‘%G’, it is treated like a value of
‘1’.  If the value being printed cannot be expressed precisely in the
specified number of digits, the value is rounded to the nearest number
that fits.