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Date: Mon, 26 Aug 2024 00:46:15 +0200
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Subject: Re: [PHP-DEV] [RFC] Default expression
To: "Rowan Tommins [IMSoP]" <imsop.php@rwec.co.uk>, internals@lists.php.net
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From: bobwei9@hotmail.com (Bob Weinand)

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On 26.8.2024 00:31:57, Rowan Tommins [IMSoP] wrote:
> I'm not an expert on parsers, and never claimed to be, so it's not particularly surprising to me that I've overlooked a reason why "expr ?: default" can't be included without also including "default ?: expr", and will just have to take your word for it.
>
> It doesn't, unfortunately, persuade me that the behaviour proposed is sensible.
>
> Rowan Tommins
> [IMSoP]

Hey Rowan,

just to state this:


It is almost never sensible to arbitrarily restrict grammars.


In the sense of "allow this expression just in a context of this given 
list of expressions". Sure, in some cases the permitted grammar doesn't 
make sense (like, why would we allow arithmetic operators on the 
left-hand side of a coalesce operation "($a + $b) ?? $c"), but that's on 
the user to write a minimal bit of sensible code.


I hope you can understand that; thanks,

Bob

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    <div class="moz-cite-prefix">On 26.8.2024 00:31:57, Rowan Tommins
      [IMSoP] wrote:<span style="white-space: pre-wrap">
</span><span style="white-space: pre-wrap">
</span></div>
    <blockquote type="cite" cite="mid:B94573C6-6AA9-4A9A-8E28-D9B158EB7344@rwec.co.uk">
      <pre wrap="" class="moz-quote-pre">I'm not an expert on parsers, and never claimed to be, so it's not particularly surprising to me that I've overlooked a reason why &quot;expr ?: default&quot; can't be included without also including &quot;default ?: expr&quot;, and will just have to take your word for it.

It doesn't, unfortunately, persuade me that the behaviour proposed is sensible.

Rowan Tommins
[IMSoP]</pre>
    </blockquote>
    <p>Hey Rowan,</p>
    <p>just to state this:</p>
    <p><br>
    </p>
    <p>It is almost never sensible to arbitrarily restrict grammars.</p>
    <p><br>
    </p>
    <p>In the sense of &quot;allow this expression just in a context of this
      given list of expressions&quot;. Sure, in some cases the permitted
      grammar doesn't make sense (like, why would we allow arithmetic
      operators on the left-hand side of a coalesce operation &quot;($a + $b)
      ?? $c&quot;), but that's on the user to write a minimal bit of sensible
      code.</p>
    <p><br>
    </p>
    <p>I hope you can understand that; thanks,<br>
    </p>
    <p>Bob<br>
    </p>
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