A question about operator*=

[JustSomeGuy]

I have a matrix class that I want to add this method to.

basically I want to multiply a matrix by a matrix or by a constant.
However, I don't want to return a matrix (refrence) from the method
as this might be a performance issue.

If one implements the method, then I suppose one is not 'required'
to return the result. However that doesn't sound like 'good' programming
style as others may not realise I've done this.

Consider these two statements:

1) a *= 2;
2) b = a *= 2;

Statement 1 doesn't make use of the return result of the *= operator, where
as
statement 2 does.

So is statement 1 faster than statement 2?

[Roel Schroeven]

Re: A question about operator*=

JustSomeGuy wrote:[color=blue]
> I have a matrix class that I want to add this method to.
>
> basically I want to multiply a matrix by a matrix or by a constant.
> However, I don't want to return a matrix (refrence) from the method
> as this might be a performance issue.[/color]

Returning a matrix can be an expensive operation, just returning a
reference has minimal impact on the performance.[color=blue]
>
> If one implements the method, then I suppose one is not 'required'
> to return the result. However that doesn't sound like 'good' programming
> style as others may not realise I've done this.[/color]

If you're afraid confusion might result, perhaps it's a better idea not
to use operator*=, but use a normal member function?
[color=blue]
> Consider these two statements:
>
> 1) a *= 2;
> 2) b = a *= 2;
>
> Statement 1 doesn't make use of the return result of the *= operator, where
> as
> statement 2 does.
>
> So is statement 1 faster than statement 2?[/color]

Of course, since it does less: the assigmnent to b doesn't happen. It
would be fairer to compare

a *= 2; b = a;
and
b = a *= 2;

I think there won't be much difference in performance. The first one is
easier to read though, in my opinion.

--
"Codito ergo sum"
Roel Schroeven

[John Harrison]

Re: A question about operator*=


"JustSomeGu y" <nope@nottellin g.com> wrote in message
news:hYcZa.6879 94$3C2.16112623 @news3.calgary. shaw.ca...[color=blue]
> I have a matrix class that I want to add this method to.
>
> basically I want to multiply a matrix by a matrix or by a constant.
> However, I don't want to return a matrix (refrence) from the method
> as this might be a performance issue.
>[/color]

There's nothing inefficient about returning a reference. Returning a
reference from *= is normal.

john