<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><!--[if !mso]><style>v\:* {behavior:url(#default#VML);}
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</o:shapelayout></xml><![endif]--></head><body lang=EN-GB link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Your first line is entirely natural.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The alternative doesn’t look right at all.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I am not aware of a more concise alternative to this general construction (assuming there are multiple case alternative, and that the work can’t be done with library functions).<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Chris<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> haskell-cafe-bounces@haskell.org [mailto:haskell-cafe-bounces@haskell.org] <b>On Behalf Of </b>tsuraan<br><b>Sent:</b> 14 March 2011 15:49<br><b>To:</b> haskell-cafe@haskell.org<br><b>Subject:</b> [Haskell-cafe] Question on a common pattern<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p><span style='font-size:10.0pt'>In my code, I'm doing this quite a lot:<br><br>x <- someIO<br>case x of<br> Opt1 -> ...<br><br>Having a line for extracting the value from the IO (or STM) and then<br>acting on the value seems unnatural. Is there a more concise way to<br>do this? This code:<br><br>case someIO of<br> Opt1 -> ...<br><br>Doesn't work, but is there something like that, that is valid?<br><br>_______________________________________________<br>Haskell-Cafe mailing list<br><a href="mailto:Haskell-Cafe@haskell.org">Haskell-Cafe@haskell.org</a><br><a href="http://www.haskell.org/mailman/listinfo/haskell-cafe">http://www.haskell.org/mailman/listinfo/haskell-cafe</a></span> <o:p></o:p></p><div class=MsoNormal align=center style='text-align:center'><hr size=1 width="100%" noshade style='color:#A0A0A0' align=center></div><p class=avgcert>No virus found in this message.<br>Checked by AVG - <a href="http://www.avg.com">www.avg.com</a><br>Version: 10.0.1204 / Virus Database: 1498/3506 - Release Date: 03/14/11<o:p></o:p></p></div></body></html>