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1 // DR 339
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2 //
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3 // Test of the use of free functions with SFINAE
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4 void foo(int) { }
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5 template<typename T> void foo(T*) { }
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6
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7 typedef char yes_type;
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8 struct no_type { char data[2]; };
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9
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10 template<typename T> T create_a();
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11
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12 template<bool, typename T = void> struct enable_if { typedef T type; };
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13 template<typename T> struct enable_if<false, T> { };
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14
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15 template<typename T>
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16 typename enable_if<(sizeof(foo(create_a<T const&>()), 1) > 0),
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17 yes_type>::type
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18 check_has_foo(const volatile T&);
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19
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20 no_type check_has_foo(...);
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21
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22 template<typename T>
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23 struct has_foo
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24 {
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25 static const bool value =
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26 (sizeof(check_has_foo(create_a<T const&>())) == sizeof(yes_type));
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27 };
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28
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29 struct X { };
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30
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31 int a1[has_foo<int>::value? 1 : -1];
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32 int a2[has_foo<long>::value? 1 : -1];
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33 int a3[has_foo<int*>::value? 1 : -1];
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34 int a4[has_foo<X>::value? -1 : 1];
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35 int a5[has_foo<int X::*>::value? -1 : 1];
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