🚀 go-pugleaf

   I noticed that that it impossible to write Function object class 
(DWP 20.3) that can be used for example as Arithmetic operation object 
and Predicate object in the same time, because both require operator() 
that can not be overloaded! So why do not have instead of one anonymous 
operator() a set of function obect methods like 
unary_operation, binary_operation, predicate, comparison 
and each function from algorithm.h will call correspondent method. 
For example, find_if will call predicate method of function object and 
transform will call unary_operation or binary_operation 
instead of operator().

In this case one can write:

class F {
   ...
   bool predicate(int); // instead of bool operator()(int);
   int unary_operation(int); // instead of int operator()(int);
   int binary_operation(int, int); // instead of int operator()(int, int);
   bool comparison(int, int); // instead of bool operator()(int, int);
};

and somewhere use F:

vector<int> v1, v2;
F f;

...
std::find_if(v1.begin(), v1.end(), f); 
 // f.predicate(int) will  be called
std::transform(v1.begin(), v1.end(), v2.begin(), v1.begin(), f);
 // f.binary_operation(int, int) will be called
std::equal(v1.begin(), v1.end(), v2.begin(), f);
 // f.comparison(int, int) will be called

--
With best regards,
Igor Boukanov (igor.boukanov@fi.uib.no).


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