A.13 library(dcg/high_order): High order grammar operations
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Availability::- use_module(library(dcg/high_order)).
Source[nondet]sequence(:Element, :Sep, ?List)//
Match or generate a sequence of Element where each pair of elements is separated by Sep. When parsing, a matched Sep commits. The final element is not committed. More formally, it matches the following sequence: 
(Element, (Sep,Element)*)?

See also sequence//5.