diff --git a/identity_type/doc/Jamfile.v2 b/identity_type/doc/Jamfile.v2 new file mode 100644 index 0000000..29ea0a9 --- /dev/null +++ b/identity_type/doc/Jamfile.v2 @@ -0,0 +1,31 @@ + +# Copyright (C) 2009-2012 Lorenzo Caminiti +# Distributed under the Boost Software License, Version 1.0 +# (see accompanying file LICENSE_1_0.txt or a copy at +# http://www.boost.org/LICENSE_1_0.txt) +# Home at http://www.boost.org/libs/utility/identity_type + +import quickbook ; +using boostbook ; + +doxygen reference : ../../../../boost/utility/identity_type.hpp + : "Reference" + PREDEFINED="DOXYGEN" + QUIET=YES + WARN_IF_UNDOCUMENTED=NO + HIDE_UNDOC_MEMBERS=YES + HIDE_UNDOC_CLASSES=YES + ALIASES=" Params=\"Parameters: \" Param{2}=\"\" EndParams=\"
\\1\\2
\" Returns=\"Returns:\" Note=\"Note:\" Warning=\"Warning:\" See=\"See:\" RefSect{1}=\"\\xmlonly\\1\\endxmlonly\" RefSectId{2}=\"\\xmlonly\\2\\endxmlonly\" RefClass{1}=\"\\xmlonly\\1\\endxmlonly\" RefFunc{1}=\"\\xmlonly\\1\\endxmlonly\" RefMacro{1}=\"\\xmlonly\\1\\endxmlonly\" " + ; + +# This target must be called "index" so to generate "index.html" file. +xml index : identity_type.qbk : reference ; + +boostbook doc : index + : html + onehtml + toc.section.depth=0 + html.stylesheet=../../../../../doc/src/boostbook.css + boost.root=../../../../.. + ; + diff --git a/identity_type/doc/html/index.html b/identity_type/doc/html/index.html new file mode 100644 index 0000000..c0dc1ee --- /dev/null +++ b/identity_type/doc/html/index.html @@ -0,0 +1,228 @@ +Boost.Utility/IdentityType 1.0.0

Boost.Utility/IdentityType 1.0.0

Lorenzo Caminiti

Copyright © 2009-2012 Lorenzo + Caminiti

+ Distributed under the Boost Software License, Version 1.0 (see accompanying + file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt) +

Table of Contents

Motivation
Solution
Templates
Abstract Types
Annex: Usage
Annex: + Implementation
Reference

+ This library allows to wrap type expressions within round parenthesis so they + can be passed to macros even when they contain commas. +

+ Consider the following macro which declares a variable named varn with the specified + type (see also var_err.cpp): +

+

#define VAR(type, n) type var ## n
+
+VAR( int, 1 );                  // OK.
+VAR( std::map<int, char>, 2 );  // Error.
+

+

+ The first macro invocation works correctly declaring a variable named var1 of type int. + However, the second macro invocation fails generating a preprocessor error + similar to the following: + 

error: macro "VAR" passed 3 arguments, but takes just 2
+

+ That is because the std::map type passed as the first macro parameter + contains a comma , not wrapped + by round parenthesis (). The preprocessor + interprets that unwrapped comma as a separation between macro parameters concluding + that a total of three (and not two) parameters are passed to the macro in the + following order: +

  1. + std::map<int +
  2. + char> +
  3. + 2 +

+ Note that, differently from the compiler, the preprocessor only recognizes + round parameters (). Angular + <> or squared [] parenthesis are not used by the preprocessor + when parsing the macro parameters. +

+ In some cases, it might be possible to workaround this issue by avoiding to + pass the type expression to the macro all together. For example, in some cases + a typedef can be used to specify + the type expression with the commas outside the macro (see also var.cpp): +

+

typedef std::map<int, char> map_type;
+VAR( map_type, 3 ); // OK.
+

+

+ When this is not possible or desired (e.g., see the function template f in the section below), the library header + boost/utility/identity_type.hpp + defines a macro BOOST_IDENTITY_TYPE + which can be used to workaround the issue while keeping the type expression + as one of the macro parameters (see also var.cpp). +

+

#include <boost/utility/identity_type.hpp>
+
+VAR( BOOST_IDENTITY_TYPE((std::map<int, char>)), 4 ); // OK.
+

+

+ This macro expands to an expression that evaluates (at compile-time) to the + specified type. The specified type is never split into multiple macro parameters + because it is always wrapped by a set of extra round parenthesis (). In fact, a total of two sets of round parenthesis + must be used: The parenthesis to invoke the macro BOOST_IDENTITY_TYPE(...) plus the inner parenthesis to wrap the + type passed to the macro BOOST_IDENTITY_TYPE((...)). +

+ This macro works on any C++03 + compiler (because it does not use variadic + macros). [1] +

+ This macro must be prefixed by typename + when used within templates. For example, let's program a macro that declares + a function parameter named argn + with the specified type (see also template.cpp): +

+

#define ARG(type, n) type arg ## n
+
+template<typename T>
+void f( // Prefix macro with `typename` in templates.
+    ARG( typename BOOST_IDENTITY_TYPE((std::map<int, T>)), 1 )
+) {
+    std::cout << arg1[0] << std::endl;
+}
+

+

+

std::map<int, char> a;
+a[0] = 'a';
+
+f<char>(a); // OK.
+// f(a);    // But error.
+

+

+ However, note that the template parameter type char + must be explicitly specified when invoking the function f<char>(a). In fact, + when the BOOST_IDENTITY_TYPE + macro is used to wrap a function template parameter, the template parameter + can no longer be implicitly determined by the compiler form the function call + as in f(a). (This + limitation does not apply to class templates because class template parameters + must always be explicitly specified.) In other words, without using the BOOST_IDENTITY_TYPE macro, C++ would + normally be able to implicitly deduce the function template parameter as shown + below: +

+

template<typename T>
+void g(
+    std::map<int, T> arg1
+) {
+    std::cout << arg1[0] << std::endl;
+}
+

+

+

g<char>(a); // OK.
+g(a);       // Also OK.
+

+

+ On some compilers (e.g., GCC), using this macro on abstract types (i.e., a + class with one or more pure virtual functions) generates a compiler error. + This can be worked around by manipulating the type adding and removing a reference + to it. +

+ Let's program a macro that performs a static assertion on a Template + Meta-Programming (TMP) meta-function (similarly to Boost.MPL BOOST_MPL_ASSERT). The BOOST_IDENTITY_TYPE macro can be used + to pass a meta-function with multiple template parameters to the assert macro + (so to handle the commas separating the template parameters). In this case, + if the meta-function is an abstract type, it needs to be manipulated adding + and removing a reference to it (see also tmp_assert.cpp): +

+

#define TMP_ASSERT(metafunction) \
+    BOOST_STATIC_ASSERT(metafunction::value)
+
+template<typename T, bool b>
+struct abstract {
+    static const bool value = b;
+    virtual void f(T const& x) = 0;
+};
+
+TMP_ASSERT(
+    boost::remove_reference<            // Add and remove
+        BOOST_IDENTITY_TYPE((           // reference for
+            boost::add_reference<       // abstract type.
+                abstract<int, true>
+            >::type
+        ))
+    >::type
+);
+

+

+ The BOOST_IDENTITY_TYPE macro + can be used either in the call of the user-defined macro (as shown by the examples + so far), or internally to the definition of the user macro. When BOOST_IDENTITY_TYPE is used internally, + the call of the user macro will only have to specify the extra parenthesis + (see also tmp_assert.cpp): +

+

#define TMP_ASSERT_PAREN(parenthesized_metafunction) \
+    /* use `BOOST_IDENTITY_TYPE` in macro definition instead of invocation */ \
+    BOOST_STATIC_ASSERT(BOOST_IDENTITY_TYPE(parenthesized_metafunction)::value)
+
+TMP_ASSERT_PAREN(( boost::is_const<std::map<int, char> const> ));
+TMP_ASSERT( BOOST_IDENTITY_TYPE((boost::is_const<std::map<int, char> const>)) );
+

+

+ However, note that the user will always have to specify + the extra parenthesis even when the macro parameters contain no comma: +

+

TMP_ASSERT_PAREN(( boost::is_const<int const> )); // Always extra `()`.
+TMP_ASSERT( boost::is_const<int const> ); // No extra `()` and no macro.
+

+

+ In some cases, using BOOST_IDENTITY_TYPE + internally might provide the best syntax for the user. For example, this is + the case for BOOST_MPL_ASSERT + because the majority of template meta-programming expressions contain unwrapped + commas so it is less confusing for the user to always specify the extra parenthesis + ((...)) instead of using BOOST_IDENTITY_TYPE: + 

BOOST_MPL_ASSERT(( // Natural syntax.
+    boost::mpl::and_<
+          boost::is_const<T>
+        , boost::is_reference<T>
+    >
+));
+

+ However, in other situations it might be preferable to not require the extra + parenthesis in common cases and handle commas as special cases using the BOOST_IDENTITY_TYPE. For example, this + is the case for BOOST_LOCAL_FUNCTION + for which always requiring the extra parenthesis ((...)) + around the types would lead to an unnatural syntax for the local function parameter + types: + 

int BOOST_LOCAL_FUNCTION( ((int&)) x, ((int&)) y ) { // Unnatural syntax.
+    return x + y;
+} BOOST_LOCAL_FUNCTION_NAME(add)
+

+ Instead requiring the user to specify BOOST_IDENTITY_TYPE + when needed allows for the more natural syntax BOOST_LOCAL_FUNCTION(int& + x, int& y) in the common cases when the parameter types + contain no comma. +

+ The implementation of this library macro is equivalent to the following: [2] + 

#include <boost/type_traits/function_traits.hpp>
+
+#define BOOST_IDENTITY_TYPE(parenthesized_type) \
+    boost::function_traits<void parenthesized_type>::arg1_type
+

+ Essentially, the type is wrapped between round parenthesis (std::map<int, + char>) + so it can be passed as a macro parameter even if it contain commas. Then the + parenthesized type is transformed into the type of a function returning void and with the specified type as the type + of the first and only argument void + (std::map<int, char>). Finally, the type of the first argument + arg1_type is extracted therefore + obtaining the original type from the parenthesized type (effectively stripping + the parenthesis from around the type). +

Reference

Wrap type expressions with round parenthesis so they can be passed to macros even if they contain commas. 

+
+BOOST_IDENTITY_TYPE(parenthesized_type)

Macro BOOST_IDENTITY_TYPE

BOOST_IDENTITY_TYPE — This macro allows to wrap the specified type expression within extra round parenthesis so the type can be passed as a single macro parameter even if it contains commas (not already wrapped within round parenthesis).

Synopsis

// In header: <boost/utility/identity_type.hpp>
+
+BOOST_IDENTITY_TYPE(parenthesized_type)

Description

Parameters:

parenthesized_typeThe type expression to be passed as macro parameter wrapped by a single set of round parenthesis (...). This type expression can contain an arbitrary number of commas.

+

This macro works on any C++03 compiler (it does not require variadic macros).

This macro must be prefixed by typename when used within templates. However, the compiler will not be able to automatically determine function template parameters when they are wrapped with this macro (these parameters need to be explicitly specified when calling the function template).

On some compilers (like GCC), using this macro on an abstract types requires to add and remove a reference to the type.


[1] + Using variadic macros, it would be possible to use a single set of parenthesis + BOOST_IDENTITY_TYPE(type) instead of two BOOST_IDENTITY_TYPE((type)) + but variadic macros are not part of C++03 (even if nowadays they are supported + by most modern compilers and they are also part of C++11). +

[2] + There is absolutely no guarantee that the macro is actually implemented using + the code listed in this documentation. This code is for explanatory purposes + only. +

diff --git a/identity_type/doc/identity_type.qbk b/identity_type/doc/identity_type.qbk new file mode 100644 index 0000000..d5107a3 --- /dev/null +++ b/identity_type/doc/identity_type.qbk @@ -0,0 +1,159 @@ + +[/ Copyright (C) 2009-2012 Lorenzo Caminiti ] +[/ Distributed under the Boost Software License, Version 1.0 ] +[/ (see accompanying file LICENSE_1_0.txt or a copy at ] +[/ http://www.boost.org/LICENSE_1_0.txt) ] +[/ Home at http://www.boost.org/libs/utility/identity_type ] + +[library Boost.Utility/IdentityType + [quickbook 1.5] + [version 1.0.0] + [copyright 2009-2012 Lorenzo Caminiti] + [purpose wraps types with round parenthesis] + [license + Distributed under the Boost Software License, Version 1.0 + (see accompanying file LICENSE_1_0.txt or a copy at + [@http://www.boost.org/LICENSE_1_0.txt]) + ] + [authors [Caminiti lorcaminiti@gmail.com, Lorenzo]] + [category Utilities] +] + +This library allows to wrap type expressions within round parenthesis so they can be passed to macros even when they contain commas. + +[import ../test/var_err.cpp] +[import ../test/var.cpp] +[import ../test/template.cpp] +[import ../test/tmp_assert.cpp] + +[section Motivation] + +Consider the following macro which declares a variable named `var`/n/ with the specified /type/ (see also [@../../test/var_err.cpp =var_err.cpp=]): + +[var_err] + +The first macro invocation works correctly declaring a variable named `var1` of type `int`. +However, the second macro invocation fails generating a preprocessor error similar to the following: + +[pre + error: macro "VAR" passed 3 arguments, but takes just 2 +] + +That is because the `std::map` type passed as the first macro parameter contains a comma `,` not wrapped by round parenthesis `()`. +The preprocessor interprets that unwrapped comma as a separation between macro parameters concluding that a total of three (and not two) parameters are passed to the macro in the following order: + +# `std::map` +# `2` + +Note that, differently from the compiler, the preprocessor only recognizes round parameters `()`. +Angular `<>` or squared `[]` parenthesis are not used by the preprocessor when parsing the macro parameters. + +[endsect] + +[section Solution] + +In some cases, it might be possible to workaround this issue by avoiding to pass the type expression to the macro all together. +For example, in some cases a `typedef` can be used to specify the type expression with the commas outside the macro (see also [@../../test/var.cpp =var.cpp=]): + +[var_typedef] + +When this is not possible or desired (e.g., see the function template `f` in the section below), the library header [headerref boost/utility/identity_type.hpp] defines a macro [macroref BOOST_IDENTITY_TYPE] which can be used to workaround the issue while keeping the type expression as one of the macro parameters (see also [@../../test/var.cpp =var.cpp=]). + +[var_ok] + +This macro expands to an expression that evaluates (at compile-time) to the specified type. +The specified type is never split into multiple macro parameters because it is always wrapped by a set of extra round parenthesis `()`. +In fact, a total of two sets of round parenthesis must be used: The parenthesis to invoke the macro `BOOST_IDENTITY_TYPE(...)` plus the inner parenthesis to wrap the type passed to the macro `BOOST_IDENTITY_TYPE((...))`. + +This macro works on any [@http://www.open-std.org/JTC1/SC22/WG21/docs/standards C++03] compiler (because it does not use [@http://en.wikipedia.org/wiki/Variadic_macro variadic macros]). +[footnote +Using variadic macros, it would be possible to use a single set of parenthesis `BOOST_IDENTITY_TYPE(`/type/`)` instead of two `BOOST_IDENTITY_TYPE((`/type/`))` but variadic macros are not part of C++03 (even if nowadays they are supported by most modern compilers and they are also part of C++11). +] + +[endsect] + +[section Templates] + +This macro must be prefixed by `typename` when used within templates. +For example, let's program a macro that declares a function parameter named `arg`/n/ with the specified /type/ (see also [@../../test/template.cpp =template.cpp=]): + +[template_f_decl] +[template_f_call] + +However, note that the template parameter type `char` must be explicitly specified when invoking the function `f(a)`. +In fact, when the [macroref BOOST_IDENTITY_TYPE] macro is used to wrap a function template parameter, the template parameter can no longer be implicitly determined by the compiler form the function call as in `f(a)`. +(This limitation does not apply to class templates because class template parameters must always be explicitly specified.) +In other words, without using the [macroref BOOST_IDENTITY_TYPE] macro, C++ would normally be able to implicitly deduce the function template parameter as shown below: + +[template_g_decl] +[template_g_call] + +[endsect] + +[section Abstract Types] + +On some compilers (e.g., GCC), using this macro on abstract types (i.e., a class with one or more pure virtual functions) generates a compiler error. +This can be worked around by manipulating the type adding and removing a reference to it. + +Let's program a macro that performs a static assertion on a [@http://en.wikipedia.org/wiki/Template_metaprogramming Template Meta-Programming] (TMP) meta-function (similarly to Boost.MPL [@http://www.boost.org/doc/libs/1_36_0/libs/mpl/doc/refmanual/assert.html `BOOST_MPL_ASSERT`]). +The [macroref BOOST_IDENTITY_TYPE] macro can be used to pass a meta-function with multiple template parameters to the assert macro (so to handle the commas separating the template parameters). +In this case, if the meta-function is an abstract type, it needs to be manipulated adding and removing a reference to it (see also [@../../test/tmp_assert.cpp =tmp_assert.cpp=]): + +[tmp_assert_abstract] + +[endsect] + +[section Annex: Usage] + +The [macroref BOOST_IDENTITY_TYPE] macro can be used either in the call of the user-defined macro (as shown by the examples so far), or internally to the definition of the user macro. +When [macroref BOOST_IDENTITY_TYPE] is used internally, the call of the user macro will only have to specify the extra parenthesis (see also [@../../test/tmp_assert.cpp =tmp_assert.cpp=]): + +[tmp_assert_alternative] + +However, note that the user will /always/ have to specify the extra parenthesis even when the macro parameters contain no comma: + +[tmp_assert_alternative_always] + +In some cases, using [macroref BOOST_IDENTITY_TYPE] internally might provide the best syntax for the user. +For example, this is the case for `BOOST_MPL_ASSERT` because the majority of template meta-programming expressions contain unwrapped commas so it is less confusing for the user to always specify the extra parenthesis `((...))` instead of using [macroref BOOST_IDENTITY_TYPE]: + + BOOST_MPL_ASSERT(( // Natural syntax. + boost::mpl::and_< + boost::is_const + , boost::is_reference + > + )); + +However, in other situations it might be preferable to not require the extra parenthesis in common cases and handle commas as special cases using the [macroref BOOST_IDENTITY_TYPE]. +For example, this is the case for `BOOST_LOCAL_FUNCTION` for which always requiring the extra parenthesis `((...))` around the types would lead to an unnatural syntax for the local function parameter types: + + int BOOST_LOCAL_FUNCTION( ((int&)) x, ((int&)) y ) { // Unnatural syntax. + return x + y; + } BOOST_LOCAL_FUNCTION_NAME(add) + +Instead requiring the user to specify [macroref BOOST_IDENTITY_TYPE] when needed allows for the more natural syntax `BOOST_LOCAL_FUNCTION(int& x, int& y)` in the common cases when the parameter types contain no comma. + +[endsect] + +[section Annex: Implementation] + +The implementation of this library macro is equivalent to the following: +[footnote +There is absolutely no guarantee that the macro is actually implemented using the code listed in this documentation. +This code is for explanatory purposes only. +] + + #include + + #define BOOST_IDENTITY_TYPE(parenthesized_type) \ + boost::function_traits::arg1_type + +Essentially, the type is wrapped between round parenthesis `(std::map)` so it can be passed as a macro parameter even if it contain commas. +Then the parenthesized type is transformed into the type of a function returning `void` and with the specified type as the type of the first and only argument `void (std::map)`. +Finally, the type of the first argument `arg1_type` is extracted therefore obtaining the original type from the parenthesized type (effectively stripping the parenthesis from around the type). + +[endsect] + +[xinclude reference.xml] + diff --git a/identity_type/index.html b/identity_type/index.html new file mode 100644 index 0000000..00b3362 --- /dev/null +++ b/identity_type/index.html @@ -0,0 +1,15 @@ + + + + + + + Automatic redirection failed, click this + link  
+

© Copyright Lorenzo Caminiti, 2009-2012

+

Distributed under the Boost Software License, Version 1.0 (see + accompanying file + LICENSE_1_0.txt or a copy at + www.boost.org/LICENSE_1_0.txt)

+ + diff --git a/identity_type/test/Jamfile.v2 b/identity_type/test/Jamfile.v2 new file mode 100644 index 0000000..2f0bdac --- /dev/null +++ b/identity_type/test/Jamfile.v2 @@ -0,0 +1,14 @@ + +# Copyright (C) 2009-2012 Lorenzo Caminiti +# Distributed under the Boost Software License, Version 1.0 +# (see accompanying file LICENSE_1_0.txt or a copy at +# http://www.boost.org/LICENSE_1_0.txt) +# Home at http://www.boost.org/libs/utility/identity_type + +import testing ; + +compile-fail var_err.cpp ; +run var.cpp ; +run template.cpp ; +run tmp_assert.cpp ; + diff --git a/identity_type/test/template.cpp b/identity_type/test/template.cpp new file mode 100644 index 0000000..ec42628 --- /dev/null +++ b/identity_type/test/template.cpp @@ -0,0 +1,48 @@ + +// Copyright (C) 2009-2012 Lorenzo Caminiti +// Distributed under the Boost Software License, Version 1.0 +// (see accompanying file LICENSE_1_0.txt or a copy at +// http://www.boost.org/LICENSE_1_0.txt) +// Home at http://www.boost.org/libs/utility/identity_type + +#include +#include +#include + +//[template_f_decl +#define ARG(type, n) type arg ## n + +template +void f( // Prefix macro with `typename` in templates. + ARG( typename BOOST_IDENTITY_TYPE((std::map)), 1 ) +) { + std::cout << arg1[0] << std::endl; +} +//] + +//[template_g_decl +template +void g( + std::map arg1 +) { + std::cout << arg1[0] << std::endl; +} +//] + +int main() { + //[template_f_call + std::map a; + a[0] = 'a'; + + f(a); // OK. + // f(a); // But error. + //] + + //[template_g_call + g(a); // OK. + g(a); // Also OK. + //] + + return 0; +} + diff --git a/identity_type/test/tmp_assert.cpp b/identity_type/test/tmp_assert.cpp new file mode 100644 index 0000000..17755cb --- /dev/null +++ b/identity_type/test/tmp_assert.cpp @@ -0,0 +1,51 @@ + +// Copyright (C) 2009-2012 Lorenzo Caminiti +// Distributed under the Boost Software License, Version 1.0 +// (see accompanying file LICENSE_1_0.txt or a copy at +// http://www.boost.org/LICENSE_1_0.txt) +// Home at http://www.boost.org/libs/utility/identity_type + +#include +#include +#include +#include +#include +#include + +//[tmp_assert_abstract +#define TMP_ASSERT(metafunction) \ + BOOST_STATIC_ASSERT(metafunction::value) + +template +struct abstract { + static const bool value = b; + virtual void f(T const& x) = 0; +}; + +TMP_ASSERT( + boost::remove_reference< // Add and remove + BOOST_IDENTITY_TYPE(( // reference for + boost::add_reference< // abstract type. + abstract + >::type + )) + >::type +); +//] + +//[tmp_assert_alternative +#define TMP_ASSERT_PAREN(parenthesized_metafunction) \ + /* use `BOOST_IDENTITY_TYPE` in macro definition instead of invocation */ \ + BOOST_STATIC_ASSERT(BOOST_IDENTITY_TYPE(parenthesized_metafunction)::value) + +TMP_ASSERT_PAREN(( boost::is_const const> )); +TMP_ASSERT( BOOST_IDENTITY_TYPE((boost::is_const const>)) ); +//] + +//[tmp_assert_alternative_always +TMP_ASSERT_PAREN(( boost::is_const )); // Always extra `()`. +TMP_ASSERT( boost::is_const ); // No extra `()` and no macro. +//] + +int main() { return 0; } + diff --git a/identity_type/test/var.cpp b/identity_type/test/var.cpp new file mode 100644 index 0000000..896aa03 --- /dev/null +++ b/identity_type/test/var.cpp @@ -0,0 +1,26 @@ + +// Copyright (C) 2009-2012 Lorenzo Caminiti +// Distributed under the Boost Software License, Version 1.0 +// (see accompanying file LICENSE_1_0.txt or a copy at +// http://www.boost.org/LICENSE_1_0.txt) +// Home at http://www.boost.org/libs/utility/identity_type + +#include + +#define VAR(type, n) type var ## n + +VAR( int, 1 ); // OK. + +//[var_typedef +typedef std::map map_type; +VAR( map_type, 3 ); // OK. +//] + +//[var_ok +#include + +VAR( BOOST_IDENTITY_TYPE((std::map)), 4 ); // OK. +//] + +int main() { return 0; } + diff --git a/identity_type/test/var_err.cpp b/identity_type/test/var_err.cpp new file mode 100644 index 0000000..7ba0c52 --- /dev/null +++ b/identity_type/test/var_err.cpp @@ -0,0 +1,18 @@ + +// Copyright (C) 2009-2012 Lorenzo Caminiti +// Distributed under the Boost Software License, Version 1.0 +// (see accompanying file LICENSE_1_0.txt or a copy at +// http://www.boost.org/LICENSE_1_0.txt) +// Home at http://www.boost.org/libs/utility/identity_type + +#include + +//[var_err +#define VAR(type, n) type var ## n + +VAR( int, 1 ); // OK. +VAR( std::map, 2 ); // Error. +//] + +int main() { return 0; } +