4. Match Specifications in Erlang
4 Match Specifications in Erlang
A "match specification" (match_spec) is an Erlang term describing a small "program" that tries to match something. It can be used to either control tracing with erlang:trace_pattern/3 or to search for objects in an ETS table with for example ets:select/2. The match specification in many ways works like a small function in Erlang, but is interpreted/compiled by the Erlang runtime system to something much more efficient than calling an Erlang function. The match specification is also very limited compared to the expressiveness of real Erlang functions.
The most notable difference between a match specification and an Erlang fun is the syntax. Match specifications are Erlang terms, not Erlang code. Also, a match specification has a strange concept of exceptions:
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An exception (suc
