Added explanation and example for undefined associativity in reduce #5086
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| The associativity of the reduction is implementation-dependent. This means | ||
| that you can't use non associative operations like ``-`` because it is | ||
| undefined whether ``reduce(-,[1,2,3])`` should be evaluated as ``(1-2)-3`` | ||
| or ``1-(2-3)``. This is because errors tend to accumulate, and it is often |
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Also: implementations might use parallel evaluation, a data structure might be traversed fastest one way or the other, etc. You might also cross-reference to foldl and foldr here.
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I don't believe that we have foldl or foldr yet.
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Consider it a note for the future then.
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Pulling this now, but could probably use a polish step. |
pao
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Dec 10, 2013
Added explanation and example for undefined associativity in reduce
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Some issues has been raised about how
reduceworks, and whatundefined associativitymeans. This change improves the documentation in my opinion, but there is always a question about style.