Guido> Andrew appears to say that if you object against '' in 'abc' not Guido> raising an exception, you should also object against the other one; Guido> but his real point is the corollary: since you don't object against Guido> giving 'ab' in 'abc' new meaning, you shouldn't object against a new Guido> meaning for '' in 'abc' either -- at least not based on the argument Guido> of breaking code. Whenever we say that a change doesn't break code, Guido> we almost always imply "except code that depends on a particular thing Guido> raising an exception". Exactly. Guido> Tim is arguing that '' in 'abc' is not a useful question to ask. The Guido> usefulness of the exception is not that it's a feature on which Guido> correct programs depend, but that it's an early warning that your Guido> program is broken. Losing that early warning sign would mean more Guido> time wasted debugging. Yes. Guido> OTOH I'm worried that some code doing some mathematical proof using Guido> substring relationships would find it irritating to have to work Guido> around the irregularity. But I admit that this is a purely Guido> theoretical fear for now. Also yes. On the other hand, I have a practical fear: There are lots of different ways of asking whether a string s contains a substring s1. If those ways behave in diverse manners when s1 is empty, I am going to have to remember which way to obtain which behavior. I would really like to avoid having to do that. -- Andrew Koenig, ark@research.att.com, http://www.research.att.com/info/ark
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