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I was under the impression that the main reason GHC requires .hs-boot files is that nobody has had the time or inclination to make it resolve circular dependencies automatically, and not an intentional design decision to encourage &quot;good design&quot;.<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;
color:#1F497D">Indeed.&nbsp; I’ve added some notes here
<a href="http://hackage.haskell.org/trac/ghc/ticket/1409#comment:37">http://hackage.haskell.org/trac/ghc/ticket/1409#comment:37</a><o:p></o:p></span></p>
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color:#1F497D"><o:p>&nbsp;</o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;
color:#1F497D">Simon<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;
color:#1F497D"><o:p>&nbsp;</o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:
&quot;Tahoma&quot;,&quot;sans-serif&quot;">From:</span></b><span lang="EN-US" style="font-size:10.0pt;
font-family:&quot;Tahoma&quot;,&quot;sans-serif&quot;"> haskell-cafe-bounces@haskell.org [mailto:haskell-cafe-bounces@haskell.org]
<b>On Behalf Of </b>Daniel Peebles<br>
<b>Sent:</b> 07 September 2010 06:06<br>
<b>To:</b> Mathew de Detrich<br>
<b>Cc:</b> Ivan Lazar Miljenovic; haskell<br>
<b>Subject:</b> Re: [Haskell-cafe] circular imports<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p>&nbsp;</o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">I was under the impression that the main reason GHC requires .hs-boot files is that nobody has had the time or inclination to make it resolve circular dependencies automatically, and not an intentional design
 decision to encourage &quot;good design&quot;.<o:p></o:p></p>
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<p class="MsoNormal">On Tue, Sep 7, 2010 at 6:51 AM, Mathew de Detrich &lt;<a href="mailto:deteego@gmail.com">deteego@gmail.com</a>&gt; wrote:<o:p></o:p></p>
<p class="MsoNormal">I had the same issue zonks ago, and I resorted to using the hs-boot file method as well (which worked fine)<o:p></o:p></p>
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<p class="MsoNormal">Which I guess brings me to my second point, is this something that GHC should do automatically when it sees circular&nbsp;dependencies? When I asked about it earlier on #haskell, I was told that its better that way because it discourages making
 bad design through circular&nbsp;dependencies&nbsp;(yet in my case and I assume the other cases as well, not using the hs-boot method would have made the design much worse). Are there any cases in particular where people would be encouraged to make interface design
 with circular&nbsp;dependencies&nbsp;(and that design be deemed as horrible) as opposed to what seems to be more realistic case where circular&nbsp;dependencies&nbsp;rarely crop up, and when they do they actually make the design better?<o:p></o:p></p>
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<p class="MsoNormal">On Tue, Sep 7, 2010 at 1:48 PM, Ivan Lazar Miljenovic &lt;<a href="mailto:ivan.miljenovic@gmail.com" target="_blank">ivan.miljenovic@gmail.com</a>&gt; wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">On 7 September 2010 03:44, Edward Z. Yang &lt;<a href="mailto:ezyang@mit.edu" target="_blank">ezyang@mit.edu</a>&gt; wrote:<br>
&gt; Excerpts from Evan Laforge's message of Mon Sep 06 13:30:43 -0400 2010:<br>
&gt;&gt; I feel like the circular imports problem is worse in haskell than<br>
&gt;&gt; other languages. &nbsp;Maybe because there is a tendency to centralize all<br>
&gt;&gt; state, since you need to define it along with your state monad. &nbsp;But<br>
&gt;&gt; the state monad module must be one of the lower level ones, since all<br>
&gt;&gt; modules that use it must import it. &nbsp;However, the tendency for bits of<br>
&gt;&gt; typed data to migrate into the state means it's easy for it to<br>
&gt;&gt; eventually want to import one of its importers. &nbsp;And the state monad<br>
&gt;&gt; module gets larger and larger (the largest modules in my system are<br>
&gt;&gt; those that define state monads: 1186 lines, 706 lines, 1156<br>
&gt;&gt; lines---the rest tend to be 100--300 lines).<br>
&gt;<br>
&gt; I have used hs-boot files to this effect. &nbsp;I separated data and functionality,<br>
&gt; and typeclasses, which must be in the same module as data or are considered<br>
&gt; orphaned, get definitions via a circular import.<o:p></o:p></p>
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<p class="MsoNormal">I'm just getting to the point where I have a similar problem. &nbsp;I was<br>
thinking about splitting instances off from the classes (and telling<br>
GHC to not worry about orphaned instances for the instance-only<br>
modules) but then realised that some instance declarations would be<br>
circular as well, so I have to either use hs-boot files, define<br>
everything in one big module and then re-export them in ways that make<br>
sense or define all instances in one big module (at least for those<br>
types which have circular deps among instances) and re-export<br>
accordingly.<o:p></o:p></p>
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--<br>
Ivan Lazar Miljenovic<br>
<a href="mailto:Ivan.Miljenovic@gmail.com" target="_blank">Ivan.Miljenovic@gmail.com</a><br>
<a href="http://IvanMiljenovic.wordpress.com" target="_blank">IvanMiljenovic.wordpress.com</a><br>
_______________________________________________<o:p></o:p></p>
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<p class="MsoNormal">Haskell-Cafe mailing list<br>
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