MSVC 10 range based for loop

Question

Currently in a large c++ project we are working on we have a bunch of the new style for loops like the following:

for (auto& value : values)

Up till now we have been compiling exclusively with gcc 4.6. Recently some of the codebase is being ported to windows and some of the developers want to compile in msvc++ 10 but it seems as though the new for loop syntax is not fully supported yet.

It would be highly desirable to not have to re-write all the places where this syntax occurs.

What is the best way to work around this problem?

Update: It looks as though this issue is resolved in MSVC11.

There's no way you're going to avoid some rewriting. VC++10 simply doesn't support it. And the only reason VC++11 will is because of the tireless efforts of the compiler writers, taking weekend time out to slip it into the build. — Nicol Bolas
– Nicol Bolas, Commented Feb 10, 2012 at 4:20
@NicolBolas: wow, I didn't know VC++ dev team was so devoted to their work. It's even more the pity that they are not further backed by Microsoft :x (as in: getting more devs) — Matthieu M.
– Matthieu M., Commented Feb 10, 2012 at 7:10

Mankarse · Accepted Answer · 2012-02-10 02:21:49Z

7

You could use Boost.Foreach:

//Using Xeo's example:
BOOST_FOREACH (auto& e, values) {
    std::cout << e << " ";
}

answered Feb 10, 2012 at 2:21

Mankarse

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2 Comments

Xeo Over a year ago

Note that you can actually use auto here. :)

Mankarse Over a year ago

@Xeo: Of course... I was sitting in C++03 land for a bit there (;

Xeo · Accepted Answer · 2012-02-10 02:17:09Z

3

One way would be to replace them with std::for_each and lambdas, where possible. GCC 4.6 and MSVC10 both support lambda expressions.

// before:
for(auto& e : values){
  std::cout << e << " ";
}

// after:
std::for_each(values.begin(), values.end(),
    [](a_type& e){
      std::cout << e << " ";
    });

The only caveat is that you need to actually type the element name (a_type here), and that you can't use control flow structures (break, continue, return).

Another way would be, when you need those control flow structures, to use old-style for-loops. Nothing wrong with them, especially with auto to infer the iterator type.

Yet another way might be to use the Visual Studio 11 beta when it's out, it supports range-based for loops IIRC. :)

answered Feb 10, 2012 at 2:17

Xeo

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17 Comments

shuttle87 Over a year ago

Interesting idea, but the lack of control structures is definitely an annoyance.

ildjarn Over a year ago

"Yet another way might be to use the Visual Studio 11 beta when it's out, it supports range-based for loops IIRC." Nope, not according to this blog post.

Xeo Over a year ago

@ildjarn: Yes, according to STL himself at his GoingNative 2012 panel. :) (Starting at somewhere around 38 minutes.)

ildjarn Over a year ago

Hmm, I haven't watched that yet. Are you sure he wasn't referring to VC++'s proprietary for each, in construct? Because the current VC++11 docs don't reflect support for proper C++11 range-based for yet. EDIT: Just watched it (1:39 in), you're totally correct -- (good) news to me. :-D

Greg Satir Over a year ago

@ildjarn The blog post has been updated to say that range-based for loops will be in VC11 Beta.

|

Yochai Timmer · Accepted Answer · 2014-03-27 09:46:05Z

2

You don't have to use boost.
Here's a simple macro for backwards compatibility with vs2010:

// 1600 is VS2010
#if _MSC_VER == 1600
    #define FOR_EACH(var , range) for each(var in range)
#else
    #define FOR_EACH(var , range) for (var : range)
#endif

Use it like this:

FOR_EACH(auto& e, values) {
    std::cout << e << " ";
}

answered Mar 27, 2014 at 9:46

Yochai Timmer

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Comments

Ari · Accepted Answer · 2014-05-26 03:05:42Z

0

You can use for each itself

for each (auto value in values) {
std::cout << value << endl;
}

answered May 26, 2014 at 3:05

Ari

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