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What Does Pattern Matching Mean? Pattern matching in computer science is the checking and locating of specific sequences of data of some pattern among raw data or a sequence of tokens. Unlike pattern recognition, the match has to be exact in the case of pattern matching.
The pattern is a general description of the format of the string. It can consist of text or the special characters X, A, and N preceded by an integer used as a repeating factor. X stands for any characters, A stands for any alphabetic characters, and N stands for any numeric characters.
LIKE clause is used to perform the pattern matching task in SQL. A WHERE clause is generally preceded by a LIKE clause in an SQL query.
I really like this trick. I do not know of any existing way to do this, and I don't foresee any problem with it -- which doesn't mean much, though. I can't think of any way to create a Not.
As for adding it to the standard library... perhaps. But I think it's a bit hard. On the other hand, how about talking Scalaz people into including it? It looks much more like their own bailiwick.
A possible problem with this is the bloated translation that the pattern matcher generates.
Here is the translation of the sample program, generated with scalac -print. Even -optimise fails to simplify the if (true) "_" else throw new MatchError() expressions.
Large pattern matches already generate more bytecode than is legal for a single method, and use of this combinator may amplify that problem.
If && was built into the language, perhaps the translation could be smarter. Alternatively, small improvements to -optimise could help.
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