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Name

floating_to_decimal, single_to_decimal, double_to_decimal, extended_to_decimal, quadruple_to_decimal - convert floating-point value to decimal record

Synopsis

#include <floatingpoint.h>

void single_to_decimal(single *px, decimal_mode *pm, decimal_record *pd, fp_exception_field_type *ps);

void double_to_decimal(double *px, decimal_mode *pm, decimal_record *pd, fp_exception_field_type *ps);

void extended_to_decimal(extended *px, decimal_mode *pm, decimal_record *pd, fp_exception_field_type *ps);

void quadruple_to_decimal(quadruple *px, decimal_mode *pm, decimal_record *pd, fp_exception_field_type *ps);

MT-Level

MT-Safe

Description

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

(pd->sign)*(pd->ds)*10**(pd->exponent)

is a correctly rounded approximation to *px. pd->ds has at least one and no more than 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(3) , fconvert(3) , gconvert(3) , printf(3S) , and sprintf(3S) all use double_to_decimal().

See Also

econvert(3) , fconvert(3) , gconvert(3) , printf(3S) , sprintf(3S)

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