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comparison liboctave/lo-traits.h @ 8726:0f6683a8150a

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some comments for lo-traits.h
author John W. Eaton <jwe@octave.org>
date Thu, 12 Feb 2009 03:03:59 -0500
parents d5af326a3ede
children e793865ede63
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8725:d5af326a3ede 8726:0f6683a8150a
21 */ 21 */
22 22
23 #if !defined (octave_liboctave_traits_h) 23 #if !defined (octave_liboctave_traits_h)
24 #define octave_liboctave_traits_h 1 24 #define octave_liboctave_traits_h 1
25 25
26 // Ideas for these classes taken from C++ Templates, The Complete
27 // Guide by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley
28 // (2003).
29
30 // Select a type based on the value of a constant expression.
31
26 template <bool cond, typename T1, typename T2> 32 template <bool cond, typename T1, typename T2>
27 class if_then_else; 33 class if_then_else;
28 34
29 template<typename T1, typename T2> 35 template<typename T1, typename T2>
30 class if_then_else<true, T1, T2> 36 class if_then_else<true, T1, T2>
39 { 45 {
40 public: 46 public:
41 47
42 typedef T2 result; 48 typedef T2 result;
43 }; 49 };
50
51 // Determine whether a template paramter is a class type.
44 52
45 template<typename T1> 53 template<typename T1>
46 class is_class_type 54 class is_class_type
47 { 55 {
48 private: 56 private:
60 68
61 enum { yes = sizeof (is_class_type_test<T1> (0)) == 1 }; 69 enum { yes = sizeof (is_class_type_test<T1> (0)) == 1 };
62 enum { no = ! yes }; 70 enum { no = ! yes };
63 }; 71 };
64 72
73 // Define typename ref_param<T>::type as T const& if T is a class
74 // type. Otherwise, define it to be T.
75
65 template<typename T> 76 template<typename T>
66 class ref_param 77 class ref_param
67 { 78 {
68 public: 79 public:
69 80