...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Returns the first element in the sequence.
template <typename Sequence> typenameresult_of::front
<Sequence>::type front(Sequence& seq); template <typename Sequence> typenameresult_of::front
<Sequence const>::type front(Sequence const& seq);
Parameter 
Requirement 
Description 


Model of Forward Sequence 
The sequence we wish to investigate. 
front(seq);
Return type: Returns a reference to
the first element in the sequence seq
if seq
is mutable and
e =
o
, where e
is the first element in the sequence, is a valid expression. Else, returns
a type convertible to the first element in the sequence.
Precondition: empty
(seq) == false
Semantics: Returns the first element in the sequence.
#include <boost/fusion/sequence/intrinsic/front.hpp> #include <boost/fusion/include/front.hpp>
vector
<int, int, int> v(1, 2, 3);
assert(front(v) == 1);