Ok, this is somehow what I did. With QChainage plugin, no need to create
new fields and csv table. It directly creates the point geometry layer
corresponding to xat(0)/yat(0) and xat(-1)/yat(-1) with $id field, when
well setting.
I also assume that what I was trying to do directly within the line l
Thanks Enrico for your reply and for the plugin.
I was aware of RefFunctions and has already used it for relational
questions. And I agree with Jean that such functions (and others of your
plugins) might be core functions. I've moreover reported a feature request
to improve usability of all this #