sizeof string array in for loop?

ALLERSLIT

Hey, sorry if the threadtitle is a bit in-informative but I didn't know what to call it. Ok now to my problem, I am playing around with arrays and stuff see here ->

#include <iostream>
#include <string>

using namespace std;

int main()
{
string a[] = { "one", "two", "three" };

for (int i = 0;i <3;i++)
{
    cout << a\[i\] << endl;
}
cin.get();

}

Now my problem is the "i < 3" let's say I wouldn't want to change that everytime i add another string to my array. How would I do that? Greetings!

Chris Losinger

there is a ARRAYSIZE macro you can use : ARRAYSIZE(a). #define ARRAYSIZE(a) sizeof(a)/sizeof(a[0]) i don't recommend it. but it should work.

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ALLERSLIT

Thanks!

Sauro Viti

If you are using Visual C++ you can use the macro _countof(x) which returns the size of the specified array. In your case you have to write i < _countof(a)

ALLERSLIT

I actually am using VC++, thanks for your answer!

Sauro Viti

You are welcome! :thumbsup:

Aescleal

What's wrong with asking the compiler how big the array is - it knows, it bunged the thing on the stack for you:

template <typename T, std::size_t N>
std::size_t sizeof_array( T (&)[N] )
{
return N;
}

Most decent compilers (VC++2003, 2005, 2008 and 2010, gcc 3.3 onwards) will inline that to a constant. You can extend it a bit...

template <typename T, std::size_t N>
T *beginning_of_array( T (&a)[N] )
{
return a;
}

template <typename T, std::size_t N>
T *end_of_array( T (&a)[N] )
{
return &a[ N ];
}

which means you can get away from using indexes entirely and start using algorithms to do the sort of thing you're doing in your example:

int main()
{
std::string a[] = { "One", "Two", "Three" };

std::copy( beginning\_of\_array( a ), end\_of\_array( a ), std::ostream\_iterator<std::string>( std::cout, "\\n" ) );

}

From there you're not far away from using overloaded functions to come up with a generic way of handling different aggregates of things. Cheers, Ash