[mythtv] C++ style

[Paul Woodward]

> On Wednesday 11 February 2004 13:25, steve at nexusuk.org wrote:
> > On Wed, 11 Feb 2004, John P. Poet wrote:
> > > For example, he says to always use pre-decrement/increment instead
> > > of post-decrement/increment -- when possible.  The "pre" versions
> > > can be converted into more efficient assembly language code, than
> > > the "post" versions.  The only time you should use the "post"
> > > version, is when you really need the increment/decrement to happend
> > > after the *current* value of the variable has been used in the
> > > expression.
> >
> > I would hope the optimizer on the compiler would optimize correctly,
> > afterall, it's not hard for the optimizer to spot that you're not
> > assigning the value to anything (in which case it doesn't matter if
> > you do post or pre, so the optimizer can pick the fastest).
> 
> That's only half true.  pre/post inc/decrement is also significant in
> non-assignment expressions, like "if" conditions.  In fact, the only
> time I can think of where it doesn't matter is if it's in it's own
> statement by itself, with no assignment, like:
> 
> 	foo++;
> is equivalent to
> 	++foo;
> or
> 	for (int i = someval; i < someotherval; i++)
> is equivalent to
> 	for (int i = someval; i < someotherval; ++i)
> 
> but
> 	if (somevar == ++i)
> is definitely different than
> 	if (somevar == i++)
> 

I don't think even Microsoft could come up with up with a compiler that generates such poor code that it takes a significant time to INC a register on an nGhz chip!