Re: strtoul etc.

[Nathan Myers <ncm@cantrip.org>]

Ulrich wrote: 
> Nathan Myers <ncm@cantrip.org> writes:
> 
> > Using the strtoul() family for conversion is just wrong.
> 
> It's not.  It's memory efficient and fast.  Note that the base
> parameter is not 0.

Yes, strtoul is about the fastest way to do what its spec says.
However, that spec is not appropriate for what iostream needs.

> If you implemented strtoll etc *fast* you'd know how much work it is.

I know it is a lot of work.  That's not the point.

> > While filling the buffer to pass to strtoul, you have already
> > done all of its work except for the most trivial part -- a
> > multiply-and-add.
> 
> See.  You don't even see the real problem.

The problem is that using strtoul() means the iostream function 
must do most of the same work as is done by strtoul in order to 
construct input suitable for strtoul.

There is nothing wrong with using strtoul in C code which happens 
to have what strtoul is intended to convert.  Iostream is not such 
code, and the amount of work it must to to *correctly* convert to 
strtoul's requirements is as large as, or larger than, the amount 
of work strtoul does; furthermore, it must duplicate much of what 
strtoul does and then discard the results.  This is necessarily 
(a lot) slower than integrating the operations into iostream.

Nathan Myers
ncm@cantrip.org