[ Boost ] BOOST_LOCAL_FUNCTION EXPERIENCE

 

c + +11 Lane supports the use of lambda function defined in a local nested functions , some of the algorithms determine the type defined as a local function can make the code clearer, while declaring and calling also makes it easier to maintain close . Unfortunately, any natural development platform company stays in vs2008, use the boost library to simulate a lambda expression is a bit clumsy and obscure .

 

occasionally seen on the forum boost1.50 version introduces BOOST_LOCAL_FUNCTION macro , the official described as follows :

 

http://www.boost.org/doc / libs/1_54_0/libs/local_function/doc/html/boost_localfunction/tutorial.html

 

  

   

    

Local Functions

   

  

 

 

Local functions are defined using macros from the header file boost / local_function.hpp . The macros must be used from within a declarative context (this is a limitation with respect to C + +11 lambda functions which can instead be declared also within expressions):

 

#include <boost/local_function.hpp> // This library header. 
 
... 
{ // Some declarative context. 
    ... 
    result-type BOOST_LOCAL_FUNCTION(parameters) { 
        body-code 
    } BOOST_LOCAL_FUNCTION_NAME(name) 
    ... 
} 

使用宏的方式来定义了一个嵌套的函数（虽然只是看起来像），但是也使得我们有另一种选择。BOOST_LOCAL_FUNCTION使用非常简单，官方示例代码如下：

 

  

 1 int main(void) {                            // Some local scope. 
 2     int sum = 0, factor = 10;               // Variables in scope to bind. 
 3  
 4     void BOOST_LOCAL_FUNCTION(const bind factor, bind& sum, int num) { 
 5         sum += factor * num; 
 6     } BOOST_LOCAL_FUNCTION_NAME(add) 
 7  
 8     add(1);                                 // Call the local function. 
 9     int nums[] = {2, 3}; 
10     std::for_each(nums, nums + 2, add);     // Pass it to an algorithm. 
11  
12     BOOST_TEST(sum == 60);                  // Assert final summation value. 
13     return boost::report_errors(); 
14 }