59 lines
1.5 KiB
C++
59 lines
1.5 KiB
C++
//wrapped1.cpp -- using a function wrapper as an argument
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#include <iostream>
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#include <math.h>
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#include <functional>
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using namespace std;
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template <typename T, typename F>
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T use_f(T v, F f)
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{
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static int count = 0;
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count++;
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cout << " use_f count = " << count << ", &count = " << &count << endl;
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return f(v);
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}
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class Fp
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{
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private:
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double z_;
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public:
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Fp(double z = 1.0) : z_(z) {}
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double operator()(double p) { return z_*p; }
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};
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class Fq
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{
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private:
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double z_;
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public:
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Fq(double z = 1.0) : z_(z) {}
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double operator()(double q) { return z_+ q; }
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};
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double dub(double x) {return 2.0*x;}
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int main()
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{
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double y = 1.21;
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function<double(double)> ef1 = dub;
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function<double(double)> ef2 = sqrt;
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function<double(double)> ef3 = Fq(10.0);
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function<double(double)> ef4 = Fp(10.0);
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function<double(double)> ef5 = [](double u) {return u*u;};
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function<double(double)> ef6 = [](double u) {return u+u/2.0;};
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cout << "Function pointer dub:\n";
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cout << " " << use_f(y, ef1) << endl;
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cout << "Function pointer sqrt:\n";
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cout << " " << use_f(y, ef2) << endl;
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cout << "Function object Fp:\n";
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cout << " " << use_f(y, ef3) << endl;
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cout << "Function object Fq:\n";
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cout << " " << use_f(y, ef4) << endl;
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cout << "Lambda expression 1:\n";
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cout << " " << use_f(y, ef5) << endl;
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cout << "Lambda expression 2:\n";
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cout << " " << use_f(y,ef6) << endl;
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// cin.get();
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return 0;
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}
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