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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt">I also like the proposal; however, I think it only makes sense if the set of unbound variables with the same name is treated as referring to the same identifier.&nbsp;This was, after all, the main reason for named
 holes.&nbsp;Roman expected this, and I think everybody who uses the feature will expect it.<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt">It would be endlessly confusing to have identifiers that look the same but aren't.<o:p></o:p></p>
<p class="MsoNormal"><o:p>&nbsp;</o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D">I agree that occurrences of an unbound variable with the same name can be thought of as being the same identifier -- but I do not agree that means that each
 occurrence need have the same type. Consider<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
<p class="MsoNormal" style="text-indent:36.0pt"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D">f x = (undefined &amp;&amp; True, ord undefined)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D">There are two occurrences of &#8216;undefined&#8217;, but one has type Bool, and the other has type Char.&nbsp; is that endlessly confusing?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D">I think that each hole *<b>must</b>* be independent, and effectively must have type (forall a.a), just like undefined.&nbsp; Otherwise you get into real difficulties
 about how polymorphism is affected because we don&#8217;t know how far out the sharing happens. &nbsp;I don&#8217;t think type sharing is a good reason for named holes -- indeed I think that trying to specify what sharing might mean would be plain confusing.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D">Instead, I&#8217;m proposing this simple design<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
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<![if !supportLists]><span style="font-size:11.0pt;font-family:Symbol;color:#1F497D"><span style="mso-list:Ignore">&middot;<span style="font:7.0pt &quot;Times New Roman&quot;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D">If there is no binding for &#8220;x&#8221;, &#8220;_x&#8221; or &#8220;foo_x&#8221; then they are unbound variables<o:p></o:p></span></p>
<p class="MsoListParagraph" style="margin-left:39.6pt"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
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<![if !supportLists]><span style="font-size:11.0pt;font-family:Symbol;color:#1F497D"><span style="mso-list:Ignore">&middot;<span style="font:7.0pt &quot;Times New Roman&quot;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D">With a suitable flag, any unbound variable is treated as a hole, with each occurrence having a separate type.
<b>That is, it&#8217;s just as if there was a top level binding for the variable saying foo_x :: forall a. a; foo_x = error &#8220;foo_x is undefined&#8221;, except that the compiler reports the type of each occurrence of a hole</b>.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
<p class="MsoListParagraph" style="margin-left:39.6pt;text-indent:-18.0pt;mso-list:l0 level1 lfo1">
<![if !supportLists]><span style="font-size:11.0pt;font-family:Symbol;color:#1F497D"><span style="mso-list:Ignore">&middot;<span style="font:7.0pt &quot;Times New Roman&quot;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D">Our current holes &#8220;_&#8221; are just a degenerate case of the above.<br>
<br>
<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:3.6pt"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D">Simple, uniform, explainable.<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:3.6pt"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D"><br>
Simon<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Verdana&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
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