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  1. #include <iostream>
  2.  
  3. template<typename T, typename F>
  4. size_t do_something_impl(const T& a, F& f)
  5. {
  6.    T internal_value(a);
  7.    const T& c_iv = internal_value;
  8.    // do some complicated things
  9.    // loop {
  10.    //   loop {
  11.        f(c_iv);
  12.        // do some more things
  13.    //   }
  14.    // }
  15.    return 42;
  16. }
  17.  
  18. template<typename T, typename F>
  19. size_t do_something(const T& a, F& f)
  20. {
  21.    return do_something_impl<T,F>(a, f);
  22. }
  23.  
  24. template<typename T, typename F>
  25. size_t do_something(const T& a, const F& f)
  26. {
  27.    return do_something_impl<T,const F>(a, f);
  28. }
  29.  
  30. struct ConstCallable
  31. {
  32. 	template<typename T> void operator()(const T&) const {}
  33. };
  34.  
  35. struct NotConstCallable
  36. {
  37. 	int i;
  38. 	template<typename T> void operator()(const T&) { ++i; }
  39. };
  40.  
  41. int main()
  42. {
  43. 	const ConstCallable f;
  44. 	NotConstCallable g;
  45. 	double n = 3.14159;
  46. 	do_something(n, f);
  47. 	do_something(n, ConstCallable());
  48. 	do_something(n, g);
  49. 	return 0;
  50. }
Success #stdin #stdout 0s 3292KB
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stdout 
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https://ideone.com/owj6oB
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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