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Predicate intercept/3
Availability::- use_module(library(intercept)).(can be autoloaded)
Sourceintercept(:Goal, ?Ball, :Handler)
Run Goal as call/1. If somewhere during the execution of Goal send_signal/1 is called with a Signal that unifies with Ball, run Handler and continue the execution.

This predicate is related to catch/3, but rather than aborting the execution of Goal and running Handler it continues the execution of Goal. This construct is also related to delimited continuations (see reset/3 and shift/1). It only covers one (common) use case for delimited continuations, but does so with a simpler interface, at lower overhead and without suffering from poor interaction with the cut.

Note that Ball and Handler are copied before calling the (copy) of Handler to avoid instantiation of Ball and/or Handler which can make a subsequent signal fail.

See also
intercept/4, reset/3, catch/4, broadcast_request/1.
Compatibility
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Dan said (2020-01-17T06:11:32):0 upvotes 0 0 downvotes
Picture of user Dan.

From the discussion forum: (https://swi-prolog.discourse.group/t/pushed-library-intercept/1691)

For example, assume we parse a (large) file using a grammar (see phrase_from_file/3) that has some sort of record structure. What should we do with the recognised records? We can return them in a list, but if the input is large this is a huge overhead if the records are to be asserted or written to a file. Using this interface we can use

document --> record(Record), !, { send_signal(record(Record)) }, document. document --> []. Given the above, we can assert all records into the database using the following query:

...,
intercept(phrase_from_file(File, document),
          record(Record),
          assertz(Record)).

Or, we can collect all records in a list using intercept_all/4:

...,
intercept_all(Record,
              phrase_from_file(File, document), record(Record),
              Records).

Comments are more than welcome. The interface may change based on further discussion.