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<p class="MsoNormal">What’s the approved mechanism to install multiple versions of happy/alex etc?  Eg I tried to build ghc-9.0 and got this:<o:p></o:p></p>
<p class="Code">checking for makeinfo... no<o:p></o:p></p>
<p class="Code">checking for python3... /usr/bin/python3<o:p></o:p></p>
<p class="Code">checking for ghc-pkg matching /opt/ghc/bin/ghc... /opt/ghc/bin/ghc-pkg<o:p></o:p></p>
<p class="Code">checking for happy... /home/simonpj/.cabal/bin/happy<o:p></o:p></p>
<p class="Code">checking for version of happy... 1.20.0<o:p></o:p></p>
<p class="Code">configure: error: Happy version 1.19 is required to compile GHC.<o:p></o:p></p>
<p class="Code"><o:p> </o:p></p>
<p class="MsoNormal">I so I have to<o:p></o:p></p>
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<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo2">Install happy-1.19 without overwriting the installed happy-1.20<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo2">Tell configure to use happy-1.19<o:p></o:p></li></ol>
<p class="MsoNormal">What’s the best way to do those two things?<o:p></o:p></p>
<p class="MsoNormal">Thanks<o:p></o:p></p>
<p class="MsoNormal">Simon<o:p></o:p></p>
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