System alias prev_n
can only appear in basic templates.
Previous edge prev_e
:
![](https://ultipa-images.oss-cn-beijing.aliyuncs.com/draw/draw_c1f7eca57bab439a81ab0bf42aad5f45.jpg?v='1645932626113')
- Consider the edge or node represented by a single-edge/node template shown in (a) and (b), their
prev_e
refers to their preceding edge; - Consider the edges or nodes represented by a multiple-edge template shown in (c) and (d), their
prev_e
refers to their respective preceding edge.
The red arrow in the image on the right above points to an edge that doesn't exist, conditional judgements
==
,!=
,>
,>=
,<
,<=
related to that "edge" will returntrue
by default, while result of other conditional judgements is unpredictable.