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dtoa.h#

Functions to format floating point numbers. Header for the library by David M. Gay.

Authors#

TheSilvered

Functions#

Nst_dtoa#

Synopsis:

char *Nst_dtoa(f64 value, int mode, int n_digits, int *decimal_point,
               int *sign, char **str_end)

Description:

Convert a double to an ASCII string.

Modes:

  • 0: shortest string that yields value when read in and rounded to nearest.
  • 1: like 0, but with Steele & White stopping rule; e.g. with IEEE P754 arithmetic, mode 0 gives 1e23 whereas mode 1 gives 9.999999999999999e22`.
  • 2: max(1, n_digits) significant digits; this gives a return value similar to that of ecvt, except that trailing zeros are suppressed.
  • 3: through n_digits past the decimal point; this gives a return value similar to that from fcvt, except that trailing zeros are suppressed, and n_digits can be negative.
  • 4, 5: similar to 2 and 3, respectively, but (in round-nearest mode) with the tests of mode 0 to possibly return a shorter string that rounds to value.
  • 6 through 9: Debugging modes similar to mode - 4: don't try fast floating-point estimate (if applicable).

Parameters:

  • value: the double to convert
  • mode: the mode to use to convert the number, valid modes range from
  • n_digits: the number of digits to output, the specific amount varies in regards to the mode used
  • decimal_point: pointer where to place the position of the decimal point relative to the string of digits returned, it is set to 9999 if value is NaN or Infinity
  • sign: set to 0 for positive values and to 1 for negative values, it is ignored if set to NULL
  • str_end: a pointer set to the end of the returned string, it is ignored if set to NULL

Returns:

An allocated string of digits where trailing zeroes are suppressed. This value must be freed with Nst_freedtoa.

Nst_freedtoa#

Synopsis:

void Nst_freedtoa(char *str)

Description:

Free a string returned by Nst_dtoa.

Nst_strtod#

Synopsis:

f64 Nst_strtod(const char *str, char **str_end)

Description:

Convert a string to a double.

This function works like strtod in the C standard.

Parameters:

  • str: the string to convert
  • str_end: pointer set to the character after the last digit of the parsed number, it is ignored if set to NULL

Returns:

The parsed number.