Hi Matthew, On Tue, Jan 02, 2024 at 10:50:51PM -0500, Matthew House wrote: > On Tue, Jan 2, 2024 at 8:49 PM Alejandro Colomar <alx@xxxxxxxxxx> wrote: > > The value of that macro is defined to be 2; it can't have any other > > value. > > > > ISO C defines it in > > <http://port70.net/~nsz/c/c11/n1570.html#5.2.4.2.2p11>. > > > > POSIX defines it in > > <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/float.h.html>. > > > > Maybe the definition of frexp() by ISO C and POSIX should be changed to > > define it in terms of FLT_RADIX instead of 2. > > > > Have a lovely day, > > Alex > > Every version of ISO C says (emphasis mine): > > The values given in the following list shall be replaced by constant > expressions with implementation-defined values that are *greater or > equal* in magnitude (absolute value) to those shown, with the same sign: > > -- radix of exponent representation, b > > FLT_RADIX 2 > > And POSIX defines it similarly. So FLT_RADIX can be greater than 2 (unless > the implementation defines __STDC_IEC_559__), it just can't be any less. > Indeed, the subsequent EXAMPLE 1 in ISO C sets FLT_RADIX to 16. Oops, my bad. > > Thus, since frexp(3) is defined to return a power of 2, interpreting it as > a power of FLT_RADIX is incorrect in the general case. Hmm, then it's a bug in the manual page. The function is curiously defined in terms of 2 regardless of what FLT_RADIX is. I'll fix it tomorrow, unless anyone wants to send a patch for it before that. Thank you both! Alex > > Thank you, > Matthew House > -- <https://www.alejandro-colomar.es/> Looking for a remote C programming job at the moment.
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