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For e format, the flag character '-', means that
the output should be left justified within the
field. The default is to pad with blanks on the
left. '+' character means that the conversion
will always begin with a sign (+ or -). The
blank flag character means that a non-negative
input will be preceded with a blank. If both a
'+' and a ' ' are specified, the blank flag is
ignored. The '0' flag character implies that
padding to the field width will be done with
zeros instead of blanks.
The field width is treated as the minimum number
of characters to be printed. The default is to
add no padding. Padding is with blanks by
default.
The precision, if set, is the minimum number of
digits to appear after the radix character.
Padding is with trailing 0s.
The behavior is like printf. One (hopefully the
only) exception is that the minimum number of
exponent digits is 3 instead of 2 for e and E
formats when the optional L is used before the
e, E, g, or G conversion character. The optional
L does not imply conversion to a long long
double.