Is -1 a magic number? An anti-pattern? A code smell? Quotes and guidelines from authorities

Posted by polygenelubricants on Stack Overflow See other posts from Stack Overflow or by polygenelubricants
Published on 2010-06-13T11:03:50Z Indexed on 2010/06/13 11:12 UTC
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java

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best-practices

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magic-numbers

I've seen -1 used in various APIs, most commonly when searching into a "collection" with zero-based indices, usually to indicate the "not found" index. This "works" because -1 is never a legal index to begin with. It seems that any negative number should work, but I think -1 is almost always used, as some sort of (unwritten?) convention.

I would like to limit the scope to Java at least for now. My questions are:

What are the official words from Sun regarding using -1 as a "special" return value like this?
What quotes are there regarding this issue, from e.g. James Gosling, Josh Bloch, or even other authoritative figures outside of Java?
What were some of the notable discussions regarding this issue in the past?

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