Paweł Jackowski wrote:
someglyph.next = someother discretionary.pre = someglyph
is not the same. Why?
Because a discretionary's pre, post, and replace lists are a bit special: internally the discretionary does not just have a next and a prev link for each of the head nodes, but also a 'tail' link. That last one points to the last node in the list for each of the three fields. That extra link is used during hyphenation and at end-of-line situations (those parts of the code would be much more complex == slower without it). So, when in lua you assign to <disc>.pre, that assingment also has to fix up that tail link (it does so by running the C equivalent of the node.tail() function). If the list you are assigning is well-formed, this is transparent. But yours isn't yet at that point in the code, because 'b.next' still points to 'd' at the moment the 'd.pre = b' is seen; and that confuses the internal code into an assertion failure. I admit this is obscure, but the general rule is simple: never assign a list to a node field until you are sure its internal link structure is correct. (a warning to this effect will be added to the manual). Best wishes, Taco