Compile-time error

**V8cTor** · 07-11-2015

I can't get this code to compile in Microsoft Visual Studio 2013(it compiled in code blocks).
I only need to know where the error is.
Please help

Code:

#include"stdafx.h"
#include<iostream>
using namespace std;
const long long limit = 1000001;
long long cache[limit] = { 0 };
inline long long next(long long n)
{
	if (n % 2 == 0)
		return n / 2;
	else
		return 3 * n + 1;
}
inline long long cycleLength(long long n)
{
	if (n == 1)		//base case
		return 1;
	// check if we've already cached the
	// cycle length of the current number
	if (n < limit && cache[n] != 0)	
		return cache[n];
	long long length = 1 + cycleLength(next(n));
	cache[n] = length;
	return length;
}
int main()
{
	int i, j, a, b;
	long long temp;
	while (cin >> i >> j)
	{
		long long maxLength = 0;
		if (i <= j)
			a = i, b = j;
		else
			a = j, b = i;
		for (int itr = a; itr <= b; ++itr)
		{
			temp = cycleLength(itr);
			if (maxLength < temp)
				maxLength = temp;
		}
		cout << i << ' ' << j << ' ' << maxLength << endl;
	}
}

Guest · 07-11-2015

What does the compiler say? Add a space after your include statements, for starters. Also, is the array to big for the stack maybe?

**jimblumberg** · 07-11-2015

Also, is the array to big for the stack maybe?

Since the array is in the global scope it is not created on the stack.

I can't get this code to compile in Microsoft Visual Studio 2013

Then please post the compile warning/error messages.

Jim

**V8cTor** · 07-11-2015

when i commented line 21:longlonglength = 1 + cycleLength(next(n));
all the obscure messages about include/xutility disappeared.

Here are the compile errors:

Code:

1>------ Build started: Project: 3n+1(with recursive), Configuration: Debug Win32 ------
1>  3n+1(with recursive).cpp
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(371): error C2825: '_Iter': must be a class or namespace when followed by '::'
1>          c:\users\vishal\documents\visual studio 2013\projects\challenges\3n+1(with recursive)\3n+1(with recursive)\3n+1(with recursive).cpp(21) : see reference to class template instantiation 'std::iterator_traits<__int64>' being compiled
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(371): error C2039: 'iterator_category' : is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(371): error C2146: syntax error : missing ';' before identifier 'iterator_category'
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(371): error C2602: 'std::iterator_traits<__int64>::iterator_category' is not a member of a base class of 'std::iterator_traits<__int64>'
1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(371) : see declaration of 'std::iterator_traits<__int64>::iterator_category'
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(371): error C2868: 'std::iterator_traits<__int64>::iterator_category' : illegal syntax for using-declaration; expected qualified-name
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(372): error C2825: '_Iter': must be a class or namespace when followed by '::'
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(372): error C2039: 'value_type' : is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(372): error C2146: syntax error : missing ';' before identifier 'value_type'
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(372): error C2602: 'std::iterator_traits<__int64>::value_type' is not a member of a base class of 'std::iterator_traits<__int64>'
1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(372) : see declaration of 'std::iterator_traits<__int64>::value_type'
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(372): error C2868: 'std::iterator_traits<__int64>::value_type' : illegal syntax for using-declaration; expected qualified-name
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(373): error C2825: '_Iter': must be a class or namespace when followed by '::'
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(373): error C2039: 'difference_type' : is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(373): error C2146: syntax error : missing ';' before identifier 'difference_type'
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(373): error C2602: 'std::iterator_traits<__int64>::difference_type' is not a member of a base class of 'std::iterator_traits<__int64>'
1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(373) : see declaration of 'std::iterator_traits<__int64>::difference_type'
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(373): error C2868: 'std::iterator_traits<__int64>::difference_type' : illegal syntax for using-declaration; expected qualified-name
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(375): error C2825: '_Iter': must be a class or namespace when followed by '::'
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(375): error C2039: 'pointer' : is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(375): error C2146: syntax error : missing ';' before identifier 'pointer'
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(375): error C2602: 'std::iterator_traits<__int64>::pointer' is not a member of a base class of 'std::iterator_traits<__int64>'
1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(375) : see declaration of 'std::iterator_traits<__int64>::pointer'
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(375): error C2868: 'std::iterator_traits<__int64>::pointer' : illegal syntax for using-declaration; expected qualified-name
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(376): error C2825: '_Iter': must be a class or namespace when followed by '::'
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(376): error C2039: 'reference' : is not a member of '`global namespace''
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(376): error C2146: syntax error : missing ';' before identifier 'reference'
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(376): error C2602: 'std::iterator_traits<__int64>::reference' is not a member of a base class of 'std::iterator_traits<__int64>'
1>          c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(376) : see declaration of 'std::iterator_traits<__int64>::reference'
1>c:\program files (x86)\microsoft visual studio 12.0\vc\include\xutility(376): error C2868: 'std::iterator_traits<__int64>::reference' : illegal syntax for using-declaration; expected qualified-name
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Guest · 07-11-2015

Clash with std::next? Try renaming your next function.

**jiggunjer** · 07-11-2015

I fixed it. the problem was using namespace std. move it INTO main to fix. There is an ambiguity error with xutility in visual studio.

P.s the solution was the first google hit when I entered "xutility _ITer must be namespace".

P.p.s of course a better solution is to just rename next

that way you can use your function in main() too if you need.

**Elysia** · 07-11-2015

The solution is to stop using "using namespace std".

**phantomotap** · 07-11-2015

The solution is to stop using "using namespace std".

O_o

No. The solution is to correctly use the namespace mechanism.

You can be specific in the function call.

You could use a directive in a more local scope.

You can do a lot, but you shouldn't avoid using directives.

Soma

**Elysia** · 07-11-2015

I like to avoid importing things into the global scope at all times. Can cause conflicts.

**MutantJohn** · 07-11-2015

I think you're both right (Elysia and phantom).

I hate

Code:

using namespace std;

I don't care that

Code:

std::vector<int> x;

is uglier than

Code:

vector<int> x

. I think it's much more specific and up-front what's going on with the first vector declaration.

But at the same time, phantom's right, using namespaces properly is the ideal.

**phantomotap** · 07-11-2015

I like to avoid importing things into the global scope at all times. Can cause conflicts.

O_o

The scope of the directive, or declaration if you prefer the approach, isn't causing the problem.

A shared identifier is being found which is either a better fit for the arguments used or introduces an ambiguity because no possibility represents a better fit.

The directive, the `using namespace std;` statement, within the `cycleLength` function has the same problem.

The declaration, a `using std::next;` statement, within the `cycleLength` function also has the same problem.

As I said, the solution isn't avoiding `using` statements.

If you avoid `using` statements, you'll always need to fully specify names. The approach is exactly as bad as needing to prefix library names as in the C language. Of course, you also lose Argument-dependent Name Lookup by avoiding the `using` statements.

The solution is actually learning to make the namespace mechanism work for you.

The important part of the real solution is knowing that `cycleLength` depends on a particular function and not simple any function with a compatible interface with respect to the arguments used. The `cycleLength` function specifically wants the globally declared/defined `next` function. The namespace mechanism allows you, as the developer, to accomplish exactly such specificity when and where appropriate.

You can introduce the same problem, as shown in the original post, with some simple code. I'll even go a step further by showing that the scope of the `using` statement isn't relevant when you have a problem if you don't know how to actually solve the problem.

[Edit]
I should note that putting a `using` statement at global scope in a header is a terrible practice.

A `using` statement at global scope in a header imports the name in every translation unit which includes the header.

You should limit `using` directives to a smaller scope when appearing in a header.
[/Edit]

Soma

Code:

#include <iostream>
#include <string>
namespace Scope1
{
    template
    <
        typename F
    >
    void Test
    (
        F f
    )
    {
        typename F::R s;
    }
}
void Test
(
    unsigned int f
)
{
    std::cout << "::Test" << '\n';
}
class Variant1
{
    Variant1()
    {
        using namespace Scope1;
        //Test(1); // Fail.
        ::Test(1); // Fine.
    }
};
class Variant2
{
    Variant2()
    {
        using Scope1::Test;
        //Test(2); // Fail.
        ::Test(2); // Fine.
    }
};
namespace Scope2
{
    using namespace Scope1;
    class Variant3
    {
        Variant3()
        {
            //Test(3); // Fail.
            ::Test(3); // Fine.
        }
    };
}
namespace Scope2
{
    using Scope1::Test;
    class Variant4
    {
        Variant4()
        {
            //Test(4); // Fail.
            ::Test(4); // Fine.
        }
    };
}
int main()
{
    return(0);
}

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