On Sep 5, 2010, at 7:40 AM, Mark S. Miller wrote: > http://wiki.ecmascript.org/doku.php?id=strawman:egal > > I have previously taken the position on this list that we should not add a > third equality construct to JavaScript. However, it is relevant to several > other strawmen that are likely to advance -- hasCode, Maps and Sets. Also, > its absence repeatedly bites me. I often accidentally code === when I mean > Object.eq because it's so hard to remember when ==='s brokenness matters. > Nevertheless, I am still ambivalent about adding it as standard equipment. > Opinions?
I think it's nearly mandatory, as the equivalence relation paired with Object.hashcode. A hash function is only meaningful in the context of an equivalence relation. Other possibilities: - Make Object.hashcode pair with === or == instead of Object.eq: formally impossible, because neither is actually an equivalence relation. Less formally, possible at the cost of making it impossible to use NaN as a hash key, or distinguish 0 from -0 as hash keys. - Make Object.hashcode correspond to an equivalence relation that is described but not provided as a predefined function - now actually using hashcode becomes needlessly complicated and error prone. It might even be desirable to name Object.hashcode something that makes the relationship to eq clear - Object.eqHash? On the other hand, it seems somewhat unlikely that other hash/equivalence pairs will be introduced to the standard, so maybe it doesn't matter. Regards, Maciej
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