<div class="gmail_quote"><div> </div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">I can see what&#39;s going on:  it can&#39;t tell that the &quot;a&quot; I am writing there is the same &quot;a&quot; that&#39;s in the type specification, but is there any way that I can make it identify &quot;a&quot; with the &quot;a&quot; in the specification for nextPtr?<br>

</blockquote><div><br>Lexically scoped type variables: <a href="http://www.haskell.org/ghc/docs/latest/html/users_guide/other-type-extensions.html#scoped-type-variables">http://www.haskell.org/ghc/docs/latest/html/users_guide/other-type-extensions.html#scoped-type-variables</a><br>

<br>Regards,<br>Sean <br></div></div><br>