[e, e'] == filter((ev.es-ble{i:l}(es;e;ev)); append(before(e'); cons(e'; []))) 

latex

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clarification:

es-interval{i:l}
es-interval(es; e; e')
== filter((ev.es-ble{i:l}(es; e; ev)); append(es-before(es; e'); cons(e'; []))) 

latex

Definitions	[e, e'], filter(P; l), es-ble{i:l}(es;e;e'), append(as; bs), before(e)
FDL editor aliases	es-interval