libsigc++ 2.2.10
Public Member Functions
sigc::signal< T_return, T_arg1, T_arg2, T_arg3, T_arg4, T_arg5, T_arg6, T_arg7 >::accumulated< T_accumulator > Class Template Reference

Convenience wrapper for the numbered sigc::signal# templates. More...

#include <sigc++/signal.h>

Inheritance diagram for sigc::signal< T_return, T_arg1, T_arg2, T_arg3, T_arg4, T_arg5, T_arg6, T_arg7 >::accumulated< T_accumulator >:
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Public Member Functions

 accumulated (const accumulated& src)

Detailed Description

template<class T_return, class T_arg1 = nil, class T_arg2 = nil, class T_arg3 = nil, class T_arg4 = nil, class T_arg5 = nil, class T_arg6 = nil, class T_arg7 = nil>
template <class T_accumulator>
class sigc::signal< T_return, T_arg1, T_arg2, T_arg3, T_arg4, T_arg5, T_arg6, T_arg7 >::accumulated< T_accumulator >

Convenience wrapper for the numbered sigc::signal# templates.

Like sigc::signal but the additional template parameter T_accumulator defines the accumulator type that should be used.

An accumulator is a functor that uses a pair of special iterators to step through a list of slots and calculate a return value from the results of the slot invokations. The iterators' operator*() executes the slot. The return value is buffered, so that in an expression like

 a = (*i) * (*i); 

the slot is executed only once. The accumulator must define its return value as result_type.

Example 1:
This accumulator calculates the arithmetic mean value:
 struct arithmetic_mean_accumulator
 {
   typedef double result_type;
   template<typename T_iterator>
   result_type operator()(T_iterator first, T_iterator last) const
 {
     result_type value_ = 0;
     int n_ = 0;
     for (; first != last; ++first, ++n_)
       value_ += *first;
     return value_ / n_;
   }
 };
Example 2:
This accumulator stops signal emission when a slot returns zero:
 struct interruptable_accumulator
 {
   typedef bool result_type;
   template<typename T_iterator>
   result_type operator()(T_iterator first, T_iterator last) const
 {
     for (; first != last; ++first, ++n_)
       if (!*first) return false;
     return true;
   }
 };