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bpo-45995: add "z" format specifer to coerce negative 0 to zero (GH-30049)

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Add "z" format specifier to coerce negative 0 to zero.

See https://github.com/python/cpython/issues/90153 (originally https://bugs.python.org/issue45995) for discussion.
This covers `str.format()` and f-strings.  Old-style string interpolation is not supported.

Co-authored-by: Mark Dickinson <dickinsm@gmail.com>
This commit is contained in:
John Belmonte 2022-04-11 23:34:18 +09:00 • committed by GitHub
parent dd207a6ac5
commit b0b836b20c
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16 changed files with 368 additions and 43 deletions
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22
Python/pystrtod.c
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@ -916,6 +916,18 @@ char * PyOS_double_to_string(double val,
(flags & Py_DTSF_ALT ? "#" : ""), precision,
format_code);
_PyOS_ascii_formatd(buf, bufsize, format, val, precision);
if (flags & Py_DTSF_NO_NEG_0 && buf[0] == '-') {
char *buf2 = buf + 1;
while (*buf2 == '0' || *buf2 == '.') {
++buf2;
}
if (*buf2 == 0 || *buf2 == 'e') {
size_t len = buf2 - buf + strlen(buf2);
assert(buf[len] == 0);
memmove(buf, buf+1, len);
}
}
}
/* Add sign when requested. It's convenient (esp. when formatting
@ -995,8 +1007,8 @@ static char *
format_float_short(double d, char format_code,
int mode, int precision,
int always_add_sign, int add_dot_0_if_integer,
int use_alt_formatting, const char * const *float_strings,
int *type)
int use_alt_formatting, int no_negative_zero,
const char * const *float_strings, int *type)
{
char *buf = NULL;
char *p = NULL;
@ -1022,6 +1034,11 @@ format_float_short(double d, char format_code,
assert(digits_end != NULL && digits_end >= digits);
digits_len = digits_end - digits;
if (no_negative_zero && sign == 1 &&
(digits_len == 0 || (digits_len == 1 && digits[0] == '0'))) {
sign = 0;
}
if (digits_len && !Py_ISDIGIT(digits[0])) {
/* Infinities and nans here; adapt Gay's output,
so convert Infinity to inf and NaN to nan, and
@ -1301,6 +1318,7 @@ char * PyOS_double_to_string(double val,
flags & Py_DTSF_SIGN,
flags & Py_DTSF_ADD_DOT_0,
flags & Py_DTSF_ALT,
flags & Py_DTSF_NO_NEG_0,
float_strings, type);
}
#endif // _PY_SHORT_FLOAT_REPR == 1