operator<</>> for __float128 are poore

[gpeterhoff]

generally

• hexfloat is not supported
• in the implementations, exceptions are used for flow control -> this procedure is/(has never been) sensible

Suggestions
a) via quadmath_snprintf/strtoflt128

• for gcc the operators can be updated
• this may also be possible for intel

1. reasonably current intel compilers also seem to provide quadmath_snprintf/strtoflt128. Is that correct? Then you can use these functions.
2. What relevance does __float128/_Quad still have for intel? This could then be removed if necessary.

b) via std/boost to_chars/from_chars

• std

1. If std::float128_t is available, these functions can be used
2. Possibly these functions are still implemented in gcc for __float128 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113260

• boost
  With boost 1.85 there is boost::charconv, but the functions are incompatible with the standard https://www.boost.org/doc/libs/1_85_0_beta1/libs/charconv/doc/html/charconv.html#to_chars_usage_notes_for_to_chars_for_floating_point_types
  Matt unfortunately refuses to implement them in a compatible way :-(
  So the NaN cases would have to be handled manually.

regards
Gero