On 4/30/22 05:48, Vincent Lefevre wrote:
Yes, but to be clear, POSIX says:
shall be evaluated as if by the strtod() function if the
corresponding conversion specifier is a, A, e, E, f, F, g, or G
so the number should be regarded as a double-precision number
(type double).
Yes, but POSIX does not require the C type 'double' and the C function
strtod to be implemented via IEEE-754 64-bit floating point. POSIX
allows 'double' and 'strtod' to be implemented via x86-64
extended-precision (80-bit) floating point, or by any other
floating-point type that satisfies some (weak) properties. I see no
requirement that the shell must be implemented as if by the standard c99
command with the default options.
The POSIX requirements on the implementation of 'double' and 'strtod'
are so lax that Bash 'printf' could even use IEEE-754 32-bit floating
point, if it wanted to. One could build Bash with 'gcc -mlong-double=32
-mdouble=32' assuming these options work, and the result would conform
to POSIX. (Not that I'm suggesting this!)
Concerning the compatibility, the question is: with what?
I agree that it'd be a net win for Bash to use plain 'double' here; your
discussion of the various compatibility plusses of doing that is
compelling to me.
