<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><br></div><div>The author tried to say it doesn't return. </div><div><br></div><div>In a Racket-like context, the author could have specified </div><div><br></div><div> ;; render-blog-page : request -> ∅</div><div><br></div><div>Since there are no elements in the emptyset, this specification says the same thing mathematically, using Racket's `types as sets' standard form of loose reasoning. I doubt it would have been more easily understood. </div><div><br></div><div>An MLer could have said α again because it is impossible to return something of this type if the function's domain isn't specified as such. Would this help? </div><div><br></div><div>-- Matthias</div><div><br></div><div><br></div><div><br></div><br><div><div>On Jun 13, 2011, at 5:13 PM, Rodolfo Carvalho wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">Hi,<div><br></div><div>I'm reading the <a href="http://docs.racket-lang.org/continue/">User Guide: Continue</a> and I'm puzzled with some contracts that reads:</div><div><br></div><blockquote class="gmail_quote" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex; "> <span class="Apple-style-span" style="font-family: serif; font-size: medium; "><table cellspacing="0" class="RktBlk"><tbody><tr><td style="padding-left: 0px; padding-right: 0px; vertical-align: baseline; "> <span class="RktCmt" style="font-family: monospace; color: rgb(194, 116, 31); ">;</span><span class="RktCmt" style="font-family: monospace; color: rgb(194, 116, 31); "> </span><span class="RktCmt" style="font-family: monospace; color: rgb(194, 116, 31); ">render-blog-page: request -> doesn</span><span class="RktCmt" style="font-family: monospace; color: rgb(194, 116, 31); ">'</span><span class="RktCmt" style="font-family: monospace; color: rgb(194, 116, 31); ">t</span></td> </tr><tr><td style="padding-left: 0px; padding-right: 0px; vertical-align: baseline; "><span class="RktCmt" style="font-family: monospace; color: rgb(194, 116, 31); ">;</span><span class="RktCmt" style="font-family: monospace; color: rgb(194, 116, 31); "> </span><span class="RktCmt" style="font-family: monospace; color: rgb(194, 116, 31); ">Produces an doesn</span><span class="RktCmt" style="font-family: monospace; color: rgb(194, 116, 31); ">'</span><span class="RktCmt" style="font-family: monospace; color: rgb(194, 116, 31); ">t page of the content of the</span></td> </tr><tr><td style="padding-left: 0px; padding-right: 0px; vertical-align: baseline; "><span class="RktCmt" style="font-family: monospace; color: rgb(194, 116, 31); ">;</span><span class="RktCmt" style="font-family: monospace; color: rgb(194, 116, 31); "> </span><span class="RktCmt" style="font-family: monospace; color: rgb(194, 116, 31); ">BLOG.</span></td> </tr></tbody></table></span></blockquote><div><br></div><div><br></div><div>Is it correct? What does it mean that it "produces an doesn't"?</div><div><br></div><div>[]'s</div><div><br clear="all">Rodolfo Carvalho<br> </div> _________________________________________________<br>  For list-related administrative tasks:<br>  <a href="http://lists.racket-lang.org/listinfo/users">http://lists.racket-lang.org/listinfo/users</a></blockquote></div><br></body></html>