2014-04-26 10:52:28 -04:00
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Zero-One-Infinity Rule
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2014-04-26 11:54:15 -04:00
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prov. Allow none of foo , one of foo , or any number of foo. A rule of thumb
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for software design, which instructs one to not place random limits on the
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number of instances of a given entity (such as: windows in a window system,
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letters in an OS's filenames, etc.). Specifically, one should either
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disallow the entity entirely, allow exactly one instance (an exception ), or
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allow as many as the user wants address space and memory permitting. The
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logic behind this rule is that there are often situations where it makes
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clear sense to allow one of something instead of none. However, if one
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decides to go further and allow N (for N 1), then why not N+1? And if N+1,
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then why not N+2, and so on? Once above 1, there's no excuse not to allow
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any N; hence, infinity. Many hackers recall in this connection Isaac
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Asimov's SF novel The Gods Themselves in which a character announces that
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the number 2 is impossible if you're going to believe in more than one
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universe, you might as well believe in an infinite number of them.
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