@i[[x;snd;upd]] == lmsg-spec-links(snd).@i[[x;snd]] & zupdate-spec-vars(upd).@i[[x;upd]] 

latex

---

clarification:

ecl-mng{i:l}
ecl-mng(es; i; ds; da; x; snd; upd)
== lmsg-spec-links(snd).ecl-mng-sends{i:l}(es; i; ds; da; x; l; snd)
== & zupdate-spec-vars(upd).ecl-mng-update{i:l}(es; i; ds; da; x; z; upd) 

latex

Definitions	P & Q, msg-spec-links(snd), @i[[x;snd]], xL.P(x), update-spec-vars(upd), @i[[x;upd]]
FDL editor aliases	ecl-mng