Don't compare zero exponentials in strings as equal #6749
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I noticed that the edge case "0e1" == "-0e1" also changed from true to false. |
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@chschneider Nice catch! I'm also not sure on that one. If we go by the original motivation of hash comparisons, then we should special-case the negative case... |
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As someone who's had to work around this (after struggling for a while to figure out what was going on), I welcome this change. 😄 What's the status of this patch? |
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Mailing-list discussion (https://externals.io/message/113346) wasn't particularly enthusiastic about making this change, so I'm going to close this. |
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Infamously,
md5('240610708') == md5('QNKCDZO')returns true in PHP. The reason is that' 0e462097431906509019562988736854' == '0e830400451993494058024219903391'interprets the two hashes as floating point numbers in exponential notation, and any numbers of the form0eNNNNevaluate to zero. Thus the strings are considered equal. This is usually not desirable.This patch changes the string comparison rules to treat strings that contain an exponential of the form
0eNNNNdifferently: If both sides of the comparison are a zero-exponential, then the strings will be compared lexicographically instead (which means they are only equal if they're exactly equal). If at least one side is not a zero-exponential, then the usual rules apply. We already have a similar special case for integral numbers overflowing the integer space.