components

Description

A components element encodes a starting point for each link component in a knot/link diagram. Recall that, in Regina, all knot/link diagrams are oriented.

The total number of components must be specified by the size attribute. The individual components are numbered 0, 1, 2, and so on.

The character data of this XML element should be a whitespace-separated list of tokens, each representing a starting point for traversing an individual component of the link diagram. There should be size tokens in total, representing starting points for components 0, 1, 2, ... in order.

If a component has no crossings (i.e., it is a zero-crossing unknot component), then the corresponding token should be the six-character literal string (null). Otherwise the token should be in one of the two forms ^k, representing the upper strand of crossing number k, or _k, representing the lower strand of crossing number k. Here the symbols ^ and _ are literal characters, whereas k should be replaced by a crossing number. Recall that Regina numbers crossings beginning at 0.

Attributes

Example

The following XML snippet represents the Whitehead link.

<crossings size="5">
- - + + -
</crossings>
<connections>
_1 ^1
_2 ^4
_4 ^3
_0 ^2
_3 ^0
</connections>
<components size="2">
^0 _0
</components>