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    <p>Mathematica's evaluator seems not flexible enough to do this easily. UpValues for pt indeed are applied before DownValues for Plus, but threading over lists due to Listability happens even before that. In this particular case, the following might work for you:</p> <pre><code>eval = Function[code,Block[{Plus = Plus, attr = DeleteCases[Attributes[Plus], Listable]}, SetAttributes[Plus, attr]; code], HoldAll] </code></pre> <p>To use it, wrap it around a piece of code where you want your rule for pt to apply, e.g.: </p> <pre><code>eval[{a0, a1} + pt[{b0, b1}]] </code></pre> <p>You can use $Pre as <code>$Pre = eval</code> to avoid typing eval every time, although generally I would not recommend this. Blocking Plus is a softer way of disabling some or all of its Attributes temporarily. The advantage w.r.t. clearing and setting attributes without Block is that you can not end up in a global state with Listable attribute permanently disabled, even if exception is thrown or the computation is Abort-ed. </p> <p>Since Listable attribute directly affects evaluation rather than pattern-matching (the latter may of course be affected indirectly if some pattern has to match the result of Plus threaded over a list), this should be ok in most cases. In theory, it may still lead to some unwanted effects in some cases, particularly where pattern-matching is involved. But in practice, it might be good enough. A cleaner but more complex solution would be to create a custom evaluator tailored to your needs.</p>
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    1. USLeonid Shifrin
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    1. CO+1 for confirming my suspicions about the evaluation order with regard to Listable. Was going to ask if you knew of the documentation for this, but when you know what to look for it is actually stated very clearly at http://reference.wolfram.com/mathematica/tutorial/Evaluation.html. Will add the link to my question and checkmark you for answering my question in the negative :) As for my solution, wrapping bare points in `pt` will be cleaner for my uses.
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