Re: Why is the iterator pass-by-value in the STL?
On 16 Nov., 17:59, Ruki <war...@gmail.com> wrote:
Why is the iterator pass-by-value in the STL?
I think it is more efficient and safe by passing a const
reference,isn't it?
void func(const_iterator first, const_iterator last);
void func(const_iterator const& first, const_iterator const& last);
It depends on what your function will be doing. In case you want to
iterate over the range you have to make a copy somewhere and modify
the iterator. In this case pass-by-value is preferable because the
compiler might be able to optimize away a copy in some cases. Suppose
the argument is actually a temporary object (like myvector.begin(),
rvalue). Then the compiler might be able to use it directly as a
function parameter. At least that's what I remember having read
somewhere (it was probably an article by Danny Kalev or David
Abrahams).
The rules of thumb for choosing between pass-by-value and pass-by-
const-reference are:
* If you want to modify a local copy: use pass-by-value
* If it's a "big" object you don't want to modify use a reference to
const
* If none of the above applies use pass-by-value.
Cheers!
SG
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