C++11 book notation
C++11 book notation
Could someone explain to me this notation from Stroustrup's book?
template<typename Cont, typename Pred>
std::vector<Value_type<Cont>*>
find_all(Cont& c, Pred p)
std::vector<Value_type<Cont>*> res;
for(auto& x :c)
if(p(x)) res.push_back(&x);
return res;
How should I understand value_type here? This is not a keyword from C++ and not Cont::value_type, then what?
value_type
Cont::value_type
The example is form C11 Bjarne Starstroup book.
Chapter 32.2 Algorithms snippet 4th.
Value_type
It is probably something like
template <typename T> using Value_type<T> = typename T::value_type;– NathanOliver
Aug 28 '18 at 19:44
template <typename T> using Value_type<T> = typename T::value_type;
Please also mention the title of the book, version, and page number. Stroustrup has three published books about C++, one of which is on its fourth edition.
– jaggedSpire
Aug 29 '18 at 13:52
@jaggedSpire I have this book and the snippet on page 672 doesn't match the one in question. And most probably it's not this book, as there is no mention of
Value_type in the index (of course, there is value_type).– BartoszKP
Aug 29 '18 at 20:48
Value_type
value_type
And in the book is clearly Value_type not value_type!
– Tomasz Kaleta
Sep 4 '18 at 7:25
1 Answer
1
See 28.2.4 of the book.
template<typename T>
using Value_type = typename std::iterator_trait<T>::value_type;
And now we are talking. Thanks. First non-evasive answer :)
– Tomasz Kaleta
Sep 4 '18 at 9:19
Shame 4 the rest.
– Tomasz Kaleta
Sep 4 '18 at 9:20
By the way std::iterator_traits :P
– Tomasz Kaleta
Sep 4 '18 at 9:30
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Value_typemust be defined somewhere before this code in the book– NathanOliver
Aug 28 '18 at 19:40