Re: std::vector of const values
On 22 Nov, 04:52, Dave <thedaverud...@gmail.com> wrote:
Hi all,
I have run into this problem a few times and was hoping there was a
more elegant solution than what I was doing. Suppose I have the
following code:
#include <vector>
#include <iostream>
void doStuff( const std::vector< const int* >& ints )
{
for( size_t i = 0; i != ints.size(); ++i )
std::cout << *ints[ i ] << std::endl;
}
int main()
{
int i1, i2, i3;
std::vector< int* > ints;
ints.push_back( &i1 );
ints.push_back( &i2 );
ints.push_back( &i3 );
doStuff( ints );
return 0;
}
Now, if I try to compile this (with gcc 4.3.2, though I get similar
problems with MSVC++ 2003), I get the following error:
constvector.cc: In function 'int main()':
constvector.cc:19: error: invalid initialization of reference of type
'const std::vector<const int*, std::allocator<const int*> >&' from
expression of type 'std::vector<int*, std::allocator<int*> >'
constvector.cc:5: error: in passing argument 1 of 'void doStuff(const
std::vector<const int*, std::allocator<const int*> >&)'
Which is really just saying that the parameter to doStuff() is vector<
const int* > but the argument I am passing it is vector< int* >
(without the const). To get around this, I have to create a copy of
the vector with the right template param type and then pass that to my
function.
However, it seems to me that, if the compiler wanted to, it could just
treat the argument as vector< const int* > and just proceed. So does
anyone know of a way to do that? Or am I stuck with making copies. Is
there some fundamental reason why a vector of non-const values could
not be treated as a vector of const values?
consider
void doStuff( std::vector< const int* >& ints )
This would be able to add const int* to what is actually
std::vector<int*>
Of course since it is actually passed as an immutable vector that
cannot happen but I think that that is getting too sophisticated.
One way to go would be to redefine doStuff as a template method taking
2 iterators and create an iterator adapter.
IMHO it is probably a bad idea to have vector of int* anyway.
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