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Postings from May 2005
John Macdonald wrote: > Is there a built-in operator that doesn't have a meaningful > identity value? I first thought of exponentiation, but it has > an identity value of 1 - you just have to realize that since > it is a right associative operator, the identity has to be > applied from the right. Well the identity of % is +inf (also right side only). The identities for ~| and ~^ are infinitely long bitstrings of 0's, while that for ~& is a similarly long bitstring of 1's. The chained comparison ops are weird as depending of which why you define the associativity (and thus which side's value you return when true) you get either a left side only or right side only Identity. E.g. if X<Y is left associative and returns Y when true then it has a left side identity of -inf, etc. But as I'm not sure if the chained ops are actually going to be defined defined in terms of the associativity of the binary op (the way false results propagates through messes things up), so that argument may not work. -- mark@biggar.org mark.a.biggar@comcast.netThread Previous | Thread Next