91 lines
2 KiB
C++
91 lines
2 KiB
C++
#include <iostream>
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#include <vector>
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#include <iterator>
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#define ITEMS(c) c.begin(),c.end()
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template<class T>
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class Increment
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{
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public:
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T arg;
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Increment( T a ) : arg(a) {}
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template<typename OutIt>
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T operator() ( T& value, OutIt out )
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{
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value+=arg;
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*out++ = value;
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return 1;
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}
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};
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template<class OP, typename OutIt>
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class Functor
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{
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public:
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OP & op;
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Functor( OP & o ) : op(o) {}
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// we cannot put the OutIt template here, because the functor is virtual
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virtual int operator() ( int& v, OutIt out ) = 0;
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};
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/* It is painfull to declare a Functor's derivate class with all the templates
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* because C++ can't infer templates from parameters of the constructor.
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* Thus, we rely on this helper free function, where templates can be infered.
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*
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* Instead of having to write:
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* Assign<Increment<int>, std::back_insert_iterator<std::vector<int> > > f(add_one);
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* We can just write:
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* auto f = make_Functor<Assign>( add_one, std::back_inserter(v));
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*/
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template<
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template< class, typename > class FC,
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class OP,
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typename OutIt
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>
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FC<OP,OutIt>& make_Functor( OP & op, OutIt /*out*/ )
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{
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return *(new FC<OP,OutIt>(op));
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}
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template<class OP, typename OutIt>
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class Assign : public Functor<OP, OutIt>
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{
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public:
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Assign( OP & o ) : Functor<OP, OutIt>(o) {}
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int operator() ( int& value, OutIt out )
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{
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// std::clog << value << " + " << this->op.arg << std::endl;
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return this->op(value,out);
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}
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};
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int main(void)
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{
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size_t nb = 10000;
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for( unsigned int k=0; k<nb; ++k) {
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std::vector<int> v;
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auto out = std::back_inserter(v);
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Increment<int> add_one(1);
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// we specify the output iterator here, just for type inference
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auto f = make_Functor<Assign>(add_one, out);
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int i = -1;
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size_t n = 0;
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for( unsigned int j=0; j<nb; ++j ) {
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n += f(i, out);
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}
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// std::cout << v.size() << std::endl;
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// std::copy( ITEMS(v), std::ostream_iterator<int>( std::cout, "\n") );
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}
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}
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