Re: ostream operator<< and builtin types
On Feb 7, 7:29 am, Pavel Shved <Pavel.Sh...@gmail.com> wrote:
On 6 ???, 13:48, "Erik Wikstr=F6m" <Erik-wikst...@telia.com> wrote:
Accordin to the standard it is possible for
basic_ostream::operator<<(T val), where T is a builtin arithmetic
type, to fail (and optionally throw an exception. I've been trying to
track down what would cause << to fail but have not yet been
successful, what I really want to know is whether one should bother
looking for exceptions when using code such as this to convert
arithmetic types to strings...
One should. And one sould do it even in common implementations.
Because of badbit, of course. You can't get failbit.
iostream conversions use locale abstractions to handle output complied
with national pecularities. According to standard, locale functions
may throw (much time has passed since i was trying to track it, so
you'd better research it again). And now assume that we are in the
locale of Mbongo-bongo savage tribe which has no representation of
numbers but integers from 1 to 10, or in medieval locale where 666 is
banned from being printed. The most straightforward solution here is
to throw an exception (bad_heretic, for example).
According to the standard, any function can throw anything for
any reason at all, with very few exceptions. From a quality of
implementation point of view, I would avoid implementations
which throw doubles just because it's Friday the 13th. The
standard specifies the behavior of std::num_put pretty closely,
and there's really no reason for it to throw. (A conforming
implementation cannot, for example, is required to generate
output in the specified base, and canot refused to convert 666.)
Or, to be more simple, if we're in envronment that has no IEEE-
compliant floating point aritmetical subsystem hence the
implementation doesn't know about NaNs, infinities etc and just fails
to print them.
If the environment doesn't have IEEE floating point, it can't
have infinities and NaNs to output, so the problem doesn't
arise.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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