Boost C++ Libraries

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cons

Description

cons is a simple Forward Sequence. It is a lisp style recursive list structure where car is the head and cdr is the tail: usually another cons structure or nil: the empty list. Fusion's list is built on top of this more primitive data structure. It is more efficient than vector when the target sequence is constructed piecemeal (a data at a time). The runtime cost of access to each element is peculiarly constant (see Recursive Inlined Functions).

Header
#include <boost/fusion/container/list/cons.hpp>
#include <boost/fusion/include/cons.hpp>
Synopsis
template <typename Car, typename Cdr = nil>
struct cons;
Template parameters

Parameter

Description

Default

Car

Head type

Cdr

Tail type

nil

Model of

Notation

nil

An empty cons

C

A cons type

l, l2

Instances of cons

car

An arbitrary data

cdr

Another cons list

s

A Forward Sequence

N

An MPL Integral Constant

Expression Semantics

Semantics of an expression is defined only where it differs from, or is not defined in Forward Sequence.

Expression

Semantics

nil()

Creates an empty list.

C()

Creates a cons with default constructed elements.

C(car)

Creates a cons with car head and default constructed tail.

C(car, cdr)

Creates a cons with car head and cdr tail.

C(s)

Copy constructs a cons from a Forward Sequence, s.

l = s

Assigns to a cons, l, from a Forward Sequence, s.

at<N>(l)

The Nth element from the beginning of the sequence; see at.

Example
cons<int, cons<float> > l(12, cons<float>(5.5f));
std::cout << at_c<0>(l) << std::endl;
std::cout << at_c<1>(l) << std::endl;

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