<div dir="ltr">Ah, yes. The set? predicate no longer distinguishes a representation. There are several predicates for the original set type, now called "hash sets": set-eq?, set-eqv?, set-equal?, set-mutable?, set-immtuable?, and set-weak?. I didn't add the basic "hash-set?", but perhaps I should. It's a weird name, since "hash-set" and "hash-set!" are already existing, unrelated functions.<br>
</div><div class="gmail_extra"><br clear="all"><div>Carl Eastlund</div>
<br><br><div class="gmail_quote">On Wed, Aug 21, 2013 at 7:08 PM, J. Ian Johnson <span dir="ltr"><<a href="mailto:ianj@ccs.neu.edu" target="_blank">ianj@ccs.neu.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Okay, I can abide. However, that doesn't really get at my frustration. I'm using the set constructor, that appears to now be an immutable-custom-set with make-immutable-hash as its make-table. So what I'm looking for is not set?, but set-immutable?, as it's a distinct (family of) struct types that won't clash with the primitive data that I'm otherwise using.<br>
<span class="HOEnZb"><font color="#888888">-Ian<br>
</font></span><div class="HOEnZb"><div class="h5">----- Original Message -----<br>
From: "Carl Eastlund" <<a href="mailto:cce@ccs.neu.edu">cce@ccs.neu.edu</a>><br>
To: "J. Ian Johnson" <<a href="mailto:ianj@ccs.neu.edu">ianj@ccs.neu.edu</a>><br>
Cc: "dev" <<a href="mailto:dev@racket-lang.org">dev@racket-lang.org</a>><br>
Sent: Wednesday, August 21, 2013 6:58:56 PM GMT -05:00 US/Canada Eastern<br>
Subject: Re: [racket-dev] Lists aren't sets, but have set-like operations<br>
<br>
<br>
Ian, sets are now a generic datatype, like dictionaries. Association lists are dictionaries, and lists are now sets. They're also streams and sequences. They're not just "set-like".<br>
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<br>
<br>
Carl Eastlund<br>
<br>
<br>
On Wed, Aug 21, 2013 at 6:56 PM, J. Ian Johnson < <a href="mailto:ianj@ccs.neu.edu">ianj@ccs.neu.edu</a> > wrote:<br>
<br>
<br>
I just wasted about 2 hours tracking down a bug that ended up being due to (set? '()) now evaluating to #t. I have no problems with set-union, intersection, etc. being defined for lists, but to treat lists as sets always is perverse to me. The contracts for set operations should use set-like? for (or/c set? list?) and keep the two constructions separate.<br>
<br>
This conflation is almost as bad as treating empty list as false.<br>
<br>
-Ian<br>
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