From 5825b6c3299ed9079438976f0245ed70933434a6 Mon Sep 17 00:00:00 2001 From: Lorenzo Caminiti Date: Mon, 20 Feb 2012 20:17:07 +0000 Subject: [PATCH] Fixed test indentation and updated docs. [SVN r77080] --- identity_type/doc/html/index.html | 119 +++++++++++++++------------- identity_type/doc/identity_type.qbk | 33 ++++---- identity_type/test/template.cpp | 10 +-- identity_type/test/tmp_assert.cpp | 8 +- identity_type/test/var.cpp | 6 +- identity_type/test/var_error.cpp | 4 +- 6 files changed, 96 insertions(+), 84 deletions(-) diff --git a/identity_type/doc/html/index.html b/identity_type/doc/html/index.html index 240c80d..cc6f4b5 100644 --- a/identity_type/doc/html/index.html +++ b/identity_type/doc/html/index.html @@ -7,13 +7,14 @@ This library allows to wrap type expressions within round parenthesis so they can be passed to macros even when they contain commas.

Motivation

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

#define VAR(type, n) type var ## n
 
-VAR( int, 1 );                  // OK.
-VAR( std::map<int, char>, 2 );  // Error.
+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. @@ -45,7 +46,7 @@ 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.
+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 @@ -56,7 +57,7 @@ 

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

This macro expands to an expression that evaluates (at compile-time) to the @@ -71,14 +72,15 @@

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 argn - with the specified type (see also template.cpp): + 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 )
+    ARG(typename BOOST_IDENTITY_TYPE((std::map<int, T>)), 1)
 ) {
     std::cout << arg1[0] << std::endl;
 }
@@ -87,20 +89,20 @@
 
std::map<int, char> a;
 a[0] = 'a';
 
-f<char>(a); // OK.
-// f(a);    // But error.
+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,
+      However, note that the template parameter char
+      must be manually 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:
+      can no longer be automatically deduced by the compiler form the function call
+      as in f(a). [2] (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 automatically deduce the function template
+      parameter as shown below:
     

 
template<typename T>
 void g(
@@ -110,14 +112,14 @@
 }
 

     

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

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. + On some compilers (e.g., GCC), using this macro on abstract types (i.e., classes + 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 @@ -132,7 +134,7 @@ template<typename T, bool b> struct abstract { static const bool value = b; - virtual void f(T const& x) = 0; + virtual void f(T const& x) = 0; // Pure virtual function. }; TMP_ASSERT( @@ -147,29 +149,32 @@

Annex: Usage

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): + can be used either when calling a user-defined macro (as shown by the examples + so far), or internally in the definition of a user-defined macro (as shown + below). When BOOST_IDENTITY_TYPE + is used in the user macro definition, 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>)) );
+// Specify only extra parenthesis `((...))`.
+TMP_ASSERT_PAREN((boost::is_const<std::map<int, char> const>));
+// Specify both the extra parenthesis `((...))` and `BOOST_IDENTITY_TYPE` macro.
+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.
+
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
+      within the user macro definition 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:
@@ -181,22 +186,21 @@
 ));

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: + parenthesis in the common cases and handle commas as special cases using 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 signature: 

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& + only 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.

Annex: Implementation

- The implementation of this library macro is equivalent to the following: [2] + The implementation of this library macro is equivalent to the following: [3] 

#include <boost/type_traits/function_traits.hpp>
 
 #define BOOST_IDENTITY_TYPE(parenthesized_type) \
@@ -204,24 +208,29 @@

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 + so it can be passed as a single macro parameter even if it contains 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). + arg1_type is extracted at compile-time + using the function_traits meta-function + therefore obtaining the original type from the parenthesized type (effectively + stripping the extra parenthesis from around the specified 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.

+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] + Using variadic macros, it would be possible to require a single set of extra + 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] + This is because the implementation of BOOST_IDENTITY_TYPE + wraps the specified type within a meta-function. +

[3] 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 index 2723d33..3ef0b12 100644 --- a/identity_type/doc/identity_type.qbk +++ b/identity_type/doc/identity_type.qbk @@ -28,7 +28,7 @@ This library allows to wrap type expressions within round parenthesis so they ca [section Motivation] -Consider the following macro which declares a variable named `var`/n/ with the specified /type/ (see also [@../../test/var_error.cpp =var_error.cpp=]): +Consider the following macro which declares a variable named `var`[^['n]] with the specified [^['type]] (see also [@../../test/var_error.cpp =var_error.cpp=]): [var_error] @@ -68,7 +68,7 @@ In fact, a total of two sets of round parenthesis must be used: The parenthesis 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). +Using variadic macros, it would be possible to require a single set of extra 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] @@ -76,15 +76,18 @@ Using variadic macros, it would be possible to use a single set of parenthesis ` [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=]): +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)`. +However, note that the template parameter `char` must be manually 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 automatically deduced by the compiler form the function call as in `f(a)`. +[footnote +This is because the implementation of [macroref BOOST_IDENTITY_TYPE] wraps the specified type within a meta-function. +] (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: +In other words, without using the [macroref BOOST_IDENTITY_TYPE] macro, C++ would normally be able to automatically deduce the function template parameter as shown below: [template_g_decl] [template_g_call] @@ -93,7 +96,7 @@ In other words, without using the [macroref BOOST_IDENTITY_TYPE] macro, C++ woul [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. +On some compilers (e.g., GCC), using this macro on abstract types (i.e., classes 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`]). @@ -106,8 +109,8 @@ In this case, if the meta-function is an abstract type, it needs to be manipulat [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=]): +The [macroref BOOST_IDENTITY_TYPE] macro can be used either when calling a user-defined macro (as shown by the examples so far), or internally in the definition of a user-defined macro (as shown below). +When [macroref BOOST_IDENTITY_TYPE] is used in the user macro definition, 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] @@ -115,7 +118,7 @@ However, note that the user will /always/ have to specify the extra parenthesis [tmp_assert_alternative_always] -In some cases, using [macroref BOOST_IDENTITY_TYPE] internally might provide the best syntax for the user. +In some cases, using [macroref BOOST_IDENTITY_TYPE] within the user macro definition 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. @@ -125,14 +128,14 @@ For example, this is the case for `BOOST_MPL_ASSERT` because the majority of tem > )); -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: +However, in other situations it might be preferable to not require the extra parenthesis in the common cases and handle commas as special cases using [macroref BOOST_IDENTITY_TYPE]. +For example, this is the case for [@http://www.boost.org/libs/local_function `BOOST_LOCAL_FUNCTION`] for which always requiring the extra parenthesis `((...))` around the types would lead to an unnatural syntax for the local function signature: 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. +Instead requiring the user to specify [macroref BOOST_IDENTITY_TYPE] only 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] @@ -149,9 +152,9 @@ This code is for explanatory purposes only. #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. +Essentially, the type is wrapped between round parenthesis `(std::map)` so it can be passed as a single macro parameter even if it contains 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). +Finally, the type of the first argument `arg1_type` is extracted at compile-time using the `function_traits` meta-function therefore obtaining the original type from the parenthesized type (effectively stripping the extra parenthesis from around the specified type). [endsect] diff --git a/identity_type/test/template.cpp b/identity_type/test/template.cpp index ec42628..dfc1097 100644 --- a/identity_type/test/template.cpp +++ b/identity_type/test/template.cpp @@ -14,7 +14,7 @@ template void f( // Prefix macro with `typename` in templates. - ARG( typename BOOST_IDENTITY_TYPE((std::map)), 1 ) + ARG(typename BOOST_IDENTITY_TYPE((std::map)), 1) ) { std::cout << arg1[0] << std::endl; } @@ -34,13 +34,13 @@ int main() { std::map a; a[0] = 'a'; - f(a); // OK. - // f(a); // But error. + f(a); // OK... + // f(a); // ... but error. //] //[template_g_call - g(a); // OK. - g(a); // Also OK. + g(a); // OK... + g(a); // ... and also OK. //] return 0; diff --git a/identity_type/test/tmp_assert.cpp b/identity_type/test/tmp_assert.cpp index f482999..b8be643 100644 --- a/identity_type/test/tmp_assert.cpp +++ b/identity_type/test/tmp_assert.cpp @@ -39,14 +39,14 @@ TMP_ASSERT( BOOST_STATIC_ASSERT(BOOST_IDENTITY_TYPE(parenthesized_metafunction)::value) // Specify only extra parenthesis `((...))`. -TMP_ASSERT_PAREN(( boost::is_const const> )); +TMP_ASSERT_PAREN((boost::is_const const>)); // Specify both the extra parenthesis `((...))` and `BOOST_IDENTITY_TYPE` macro. -TMP_ASSERT( BOOST_IDENTITY_TYPE((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. +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 index 896aa03..9ed165d 100644 --- a/identity_type/test/var.cpp +++ b/identity_type/test/var.cpp @@ -9,17 +9,17 @@ #define VAR(type, n) type var ## n -VAR( int, 1 ); // OK. +VAR(int, 1); // OK. //[var_typedef typedef std::map map_type; -VAR( map_type, 3 ); // OK. +VAR(map_type, 3); // OK. //] //[var_ok #include -VAR( BOOST_IDENTITY_TYPE((std::map)), 4 ); // OK. +VAR(BOOST_IDENTITY_TYPE((std::map)), 4); // OK. //] int main() { return 0; } diff --git a/identity_type/test/var_error.cpp b/identity_type/test/var_error.cpp index b69817d..efb9743 100644 --- a/identity_type/test/var_error.cpp +++ b/identity_type/test/var_error.cpp @@ -10,8 +10,8 @@ //[var_error #define VAR(type, n) type var ## n -VAR( int, 1 ); // OK. -VAR( std::map, 2 ); // Error. +VAR(int, 1); // OK. +VAR(std::map, 2); // Error. //] int main() { return 0; }