list

Description

list is a Forward Sequence of heterogenous typed data built on top of cons. 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/sequence/container/list.hpp>
#include <boost/fusion/sequence/container/list/list_forward.hpp>

Synopsis

template <
    typename T0 = unspecified
  , typename T1 = unspecified
  , typename T2 = unspecified
    ...
  , typename TN = unspecified
>
struct list;

The variadic class interface accepts 0 to FUSION_MAX_LIST_SIZE elements, where FUSION_MAX_LIST_SIZE is a user definable predefined maximum that defaults to 10. Example:

list<int, char, double>

You may define the preprocessor constant FUSION_MAX_LIST_SIZE before including any Fusion header to change the default. Example:

#define FUSION_MAX_LIST_SIZE 20

Template parameters

Parameter	Description	Default
`T0`...`TN`	Element types	unspecified-type

Model of

Forward Sequence

Notation

L: A list type
l: An instance of list
e0...en: Heterogeneous values
s: A Forward Sequence
N: An Integral Constant

Expression Semantics

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

Expression	Semantics
`L()`	Creates a list with default constructed elements.
`L(e0, e1,... en)`	Creates a list with elements `e0`...`en`.
`L(s)`	Copy constructs a list from a Forward Sequence, `s`.
`l = s`	Assigns to a list, `l`, from a Forward Sequence, `s`.
`at<N>(l)`	The Nth element from the beginning of the sequence; see `at`.

note at<n>(l) is provided for convenience and compatibility with the original Boost.Tuple library, despite list being a Forward Sequence only (at is supposed to be a Random Access Sequence requirement). The runtime complexity of at is constant (see Recursive Inlined Functions).

Example

list<int, float> l(12, 5.5f);
std::cout << at<0>(l) << std::endl;
std::cout << at<1>(l) << std::endl;