Ah! Very good points, thank you for the explanation.<br clear="all"><br>_Nick_<br><br>
<br><br><div class="gmail_quote">On Thu, Aug 5, 2010 at 2:13 PM, Daniel Gackle <span dir="ltr"><<a href="mailto:danielgackle@gmail.com">danielgackle@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class="im">< <span style="font-family:arial, sans-serif;font-size:13px;border-collapse:collapse">why not just use an object as the only parameter ></span><div><font face="arial, sans-serif"><span style="border-collapse:collapse"><br>
</span></font></div></div><div><font face="arial, sans-serif"><span style="border-collapse:collapse">That was the first way we did it, and we changed it for a good reason,</span></font></div>
<div><font face="arial, sans-serif"><span style="border-collapse:collapse">but my recollection of why is fuzzy. Does anybody remember?</span></font></div><div><font face="arial, sans-serif"><span style="border-collapse:collapse">The archives of this list may be helpful here.</span></font></div>
<div><font face="arial, sans-serif"><span style="border-collapse:collapse"><br></span></font></div><div><font face="arial, sans-serif"><span style="border-collapse:collapse">I believe the reason may have been that it places an undue burden</span></font></div>
<div><font face="arial, sans-serif"><span style="border-collapse:collapse">on the caller. If I want to write something like this...</span></font></div><div><font face="arial, sans-serif"><span style="border-collapse:collapse"><br>
</span></font></div><div><font face="arial, sans-serif"><span style="border-collapse:collapse"> (member item arr :key foo :test bar)</span></font></div><div><font face="arial, sans-serif"><span style="border-collapse:collapse"><br>
</span></font></div><div><font face="arial, sans-serif"><span style="border-collapse:collapse">... who is going to figure out that the last 4 arguments are really two</span></font></div>
<div><font face="arial, sans-serif"><span style="border-collapse:collapse">keyword params and bundle them into </span></font><span style="font-family:arial, sans-serif;border-collapse:collapse">{ key : foo, test : bar }?</span></div>
<div><font face="arial, sans-serif"><span style="border-collapse:collapse"><br></span></font></div><div><font face="arial, sans-serif"><span style="border-collapse:collapse">You could make the caller do it:</span></font></div>
<div><font face="arial, sans-serif"><span style="border-collapse:collapse"><br></span></font></div><div><font face="arial, sans-serif"><span style="border-collapse:collapse"> (member item arr (create :key foo :test bar))</span></font></div>
<div><font face="arial, sans-serif"><span style="border-collapse:collapse"><br></span></font></div><div><font face="arial, sans-serif"><span style="border-collapse:collapse">... but then you lose interoperability with CL, and arguably dilute the</span></font></div>
<div><font face="arial, sans-serif"><span style="border-collapse:collapse">feature to the point where you might as well not have it, since it's</span></font></div><div>
<font face="arial, sans-serif"><span style="border-collapse:collapse">easy enough to define a function that takes a js object as its last</span></font></div><div><font face="arial, sans-serif"><span style="border-collapse:collapse">parameter and picks out the keys.</span></font></div>
<div><span style="font-family:arial, sans-serif;border-collapse:collapse"><br></span></div><div><span style="font-family:arial, sans-serif;border-collapse:collapse">On the other hand, you could make PS do it by decreeing</span><span style="font-family:arial, sans-serif;border-collapse:collapse"> that</span></div>
<div><span style="font-family:arial, sans-serif;border-collapse:collapse">keywords in an arglist *always* identify keyword </span><span style="font-family:arial, sans-serif;border-collapse:collapse">params, but </span></div>
<div><span style="font-family:arial, sans-serif;border-collapse:collapse">that breaks this:</span></div><div><span style="font-family:arial, sans-serif;border-collapse:collapse"><br>
</span></div><div><span style="font-family:arial, sans-serif;border-collapse:collapse"> (member :blah arr :key foo :test bar)</span></div><div><span style="font-family:arial, sans-serif;border-collapse:collapse"><br>
</span></div><div><span style="font-family:arial, sans-serif;border-collapse:collapse">... which now generates member({blah : arr, key : foo, test : bar})</span></div><div><span style="font-family:arial, sans-serif;border-collapse:collapse">instead of the desired member("blah", arr, {k</span><span style="font-family:arial, sans-serif;border-collapse:collapse">ey : foo, test : bar}).</span></div>
<div><span style="font-family:arial, sans-serif;border-collapse:collapse">In other words, this option m</span><span style="font-family:arial, sans-serif;border-collapse:collapse">akes the semantics of keywords </span></div>
<div><span style="font-family:arial, sans-serif;border-collapse:collapse">inconsistent in PS.</span></div><div><span style="font-family:arial, sans-serif;border-collapse:collapse"><br>
</span></div><div><span style="font-family:arial, sans-serif;border-collapse:collapse">Another option is to make the PS compiler consider the signature</span></div><div><span style="font-family:arial, sans-serif;border-collapse:collapse">of the function being called before it generates the code for the call.</span></div>
<div><span style="font-family:arial, sans-serif;border-collapse:collapse">That complicates the compiler and IIRC is hard to get working in</span></div><div><span style="font-family:arial, sans-serif;border-collapse:collapse">the general case (Vladimir can comment here).</span></div>
<div><span style="font-family:arial, sans-serif;border-collapse:collapse"><br></span></div><div><span style="font-family:arial, sans-serif;border-collapse:collapse">So my recollection is that we settled on the existing method as the</span></div>
<div><span style="font-family:arial, sans-serif;border-collapse:collapse">one that places no burden on either the caller or the callee (at the source</span></div><div><span style="font-family:arial, sans-serif;border-collapse:collapse">level... obviously the JS that's generated for the callee is what does</span></div>
<div><span style="font-family:arial, sans-serif;border-collapse:collapse">all the extra work), preserves the semantics of keywords, is closest</span></div><div><span style="font-family:arial, sans-serif;border-collapse:collapse">to how CL does keyword args, and keeps the compiler simple.</span></div>
<div><div></div><div class="h5">
<div><span style="font-family:arial, sans-serif;border-collapse:collapse"><br></span></div><div><font face="arial, sans-serif"><span style="border-collapse:collapse"><br>
</span></font></div><div><font face="arial, sans-serif"><span style="border-collapse:collapse"><br></span></font></div><div><br><div class="gmail_quote">On Thu, Aug 5, 2010 at 2:47 PM, Nick Fitzgerald <span dir="ltr"><<a href="mailto:fitzgen@gmail.com" target="_blank">fitzgen@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Ok, I just realized that I completely misread your original post. I thought you were proposing the removal of defaulting to null rather than leaving the value undefined.<div>
<br></div><div>Have you done any profiling to see if there is a reasonable difference between</div>
<div><br></div><div><div><div>"function foo() {</div><div> var a;</div><div> // ... pick out and assign keyword args ...</div><div> if (a === undefined) {</div><div> a = null;</div><div> };</div>
<div> return bar(a);</div>
<div>};"</div><div><br></div></div><div>and </div><div><div><br></div><div><div>"function foo() {</div><div> var a = null;</div><div> // ... pick out and assign keyword args ...</div><div> return bar(a);</div>
<div>
};"</div></div><div><br></div></div>?</div><div><br></div><div>I just ran this very naive test in Chromium:</div><div><br></div><div><font face="'courier new', monospace">var then = +new Date;</font></div>
<div><font face="'courier new', monospace">var i = 20000;</font></div><div><font face="'courier new', monospace">while (i--) {</font></div><div><font face="'courier new', monospace"> (function () {</font></div>
<div><font face="'courier new', monospace"> var a;</font></div><div><div><font face="'courier new', monospace"> if (a === undefined) a = null;</font></div>
</div><div><font face="'courier new', monospace"> }())</font></div><div><font face="'courier new', monospace">};</font></div><div><font face="'courier new', monospace">console.log(+new Date - then);</font></div>
<div><font face="'courier new', monospace"><br><font face="arial">Which logs 70 ms.</font></font></div><div><font face="'courier new', monospace"><br>
var then = +new Date;</font></div><div><font face="'courier new', monospace">var i = 20000;</font></div><div><font face="'courier new', monospace">while (i--) {</font></div>
<div><font face="'courier new', monospace"> (function () {</font></div><div><font face="'courier new', monospace"> var a = null;</font></div><div><font face="'courier new', monospace"> }())</font></div>
<div><font face="'courier new', monospace">};</font></div><div><font face="'courier new', monospace">console.log(+new Date - then);<br><br></font><div><br>
</div><div>This one logs 71 ms.</div><div><br></div><div>This has to have come up before, but why not just use an object as the only parameter and use it's keys as the keyword arguments? I just ran the same test for that, and when the keyword was missing I got 82 ms, but when it was available, I got 56.</div>
<div><br></div><div>I think using objects would make the generated code much more readable, which trumps speed in this case IMO given that the difference is so small and the high number of iterations being performed.</div>
<div><br></div><font color="#888888">_Nick_</font><div><div></div><div><br><br>
<br><br><div class="gmail_quote">On Thu, Aug 5, 2010 at 1:24 PM, Daniel Gackle <span dir="ltr"><<a href="mailto:danielgackle@gmail.com" target="_blank">danielgackle@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Good point. I kept the null assignment for consistency with how PS does &optional<div>arguments. But this begs the question: why do we care about &optional</div><div>and &key arguments being set to null, as opposed to just leaving them undefined?</div>
<div>I'm trying to remember the reason... anybody?</div><div><br></div><div>Our experience has been that PS code works best if one treats null and undefined </div><div>as interchangeable. But that may be an artifact of running some of the same code</div>
<div>in CL as well, where there is no such distinction.</div><div><div></div><div><div><br></div><div><br><div class="gmail_quote">On Thu, Aug 5, 2010 at 1:51 PM, Nick Fitzgerald <span dir="ltr"><<a href="mailto:fitzgen@gmail.com" target="_blank">fitzgen@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">+1 from me but that doesn't mean too much.<div><br></div><div>No need to explicitly set them as `null`, because JS already has (the more semantic in this case) `undefined`.<br clear="all">
<br>_Nick_<br><br>
<br><br><div class="gmail_quote"><div><div></div><div>On Wed, Aug 4, 2010 at 12:30 PM, Daniel Gackle <span dir="ltr"><<a href="mailto:danielgackle@gmail.com" target="_blank">danielgackle@gmail.com</a>></span> wrote:<br>
</div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div></div><div>
The code that's generated for a keyword argument goes like this:<div><div><br></div><div><div>(ps (defun foo (&key a) (bar a))) => </div><div><br></div><div>(abbreviated for clarity):</div><div><br></div><div>
"function foo() {</div>
<div> var a;</div><div> // ... pick out and assign keyword args ...</div><div> if (a === undefined) {</div><div> a = null;</div><div> };</div><div> return bar(a);</div><div>};"</div></div></div>
<div>
<br></div><div>It seems to me that this could be made tighter as follows:</div><div><br></div><div><div>"function foo() {</div><div> var a = null;</div><div> // ... pick out and assign keyword args ...</div><div>
return bar(a);</div><div>};"</div></div><div><br></div><div>The only difference I can think of is when someone explicitly passes undefined</div><div>as a value for the argument, but that's an oxymoronic thing to do.</div>
<div><br></div><div>Can anyone think of a reason not to make this change? I like PS's keyword</div><div>arguments a lot, but the generated JS is bloated enough to make me wince.</div>
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