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The floating_to_decimal() functions convert the floating-point value at *px into a decimal record at *pd, observing the modes
specified in *pm and setting exceptions in *ps. If there are no IEEE exceptions, *ps will
be zero.
If *px is zero, infinity, or NaN, then only pd->sign and pd->fpclass are set. Otherwise pd->exponent
and pd->ds are also set so that
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(sig)*(pd->ds)*10**(pd->exponent)
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is a correctly rounded approximation to *px, where sig is +1 or -1, depending upon whether pd->sign
is 0 or -1. pd->ds has at least one and no more than DECIMAL_STRING_LENGTH-1 significant digits because one character is
used to terminate the string with a NULL.
pd->ds is correctly rounded according to the IEEE rounding modes in pm->rd. *ps has fp_inexact set if the result was inexact, and has fp_overflow set if the string result does not fit in pd->ds because of the limitation DECIMAL_STRING_LENGTH.
If pm->df == floating_form, then pd->ds always contains pm->ndigits significant digits. Thus if *px
== 12.34 and pm->ndigits == 8, then pd->ds will contain 12340000 and pd->exponent will contain -6.
If pm->df == fixed_form and pm->ndigits >= 0, then pd->ds always
contains pm->ndigits after the point and as many digits as necessary before the point. Since the latter is not known in advance, the total number of digits required is returned
in pd->ndigits; if that number >= DECIMAL_STRING_LENGTH, then ds is undefined. pd->exponent always gets -pm->ndigits. Thus if *px == 12.34 and pm->ndigits == 1, then pd->ds gets 123, pd->exponent gets -1, and pd->ndigits gets 3.
If pm->df == fixed_form and pm->ndigits < 0, then pd->ds always
contains -pm->ndigits trailing zeros; in other words, rounding occurs -pm->ndigits to the left of the decimal point, but the digits rounded
away are retained as zeros. The total number of digits required is in pd->ndigits. pd->exponent always gets 0. Thus if *px
== 12.34 and pm->ndigits == -1, then pd->ds gets 10, pd->exponent gets 0, and pd->ndigits
gets 2.
pd->more is not used.
econvert(3C), fconvert(3C), gconvert(3C), printf(3C), and sprintf(3C) all use double_to_decimal().
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