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<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US">August<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US">In Oberon-07 it is defined as follows:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US">The type T of the case expression (case variable) may also be a record or pointer type. Then the<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US">case labels
<b>must be extensions of T</b>, and in the statements Si labelled by Ti, the case variable is<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US">considered as of type Ti.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">PROCEDURE Draw (s: Shape)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">BEGIN<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"> CASE s OF<br>
Rectangle: ... |<br>
Circle: ... |<br>
Shape: ... </span><span lang="EN-US" style="font-size:11.0pt;font-family:Wingdings"></span><span lang="EN-US" style="font-size:11.0pt"> this is not allowed as “Shape” is not an extension of “Shape”<br>
END<br>
</span><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US">END Draw;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US">Jörg<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="font-size:12.0pt;color:black">Von:
</span></b><span style="font-size:12.0pt;color:black">Oberon <oberon-bounces@lists.inf.ethz.ch> im Auftrag von August Karlstrom <fusionfile@gmail.com><br>
<b>Datum: </b>Montag, 28. August 2023 um 12:53<br>
<b>An: </b>oberon@lists.inf.ethz.ch <oberon@lists.inf.ethz.ch><br>
<b>Betreff: </b>[Oberon] Case statements containing base type labels<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Given the declarations<br>
<br>
Shape = RECORD x, y: REAL END<br>
Rectangle = RECORD (Shape) w, h: REAL END<br>
Circle = RECORD (Shape) r: REAL END<br>
<br>
does a case statement containing labels for all three types have well <br>
defined behavior?<br>
<br>
CASE s OF<br>
Rectangle: ... |<br>
Circle: ... |<br>
Shape: ...<br>
END<br>
<br>
In this case a rectangle and a circle respectively is also a shape so <br>
it's not clear what label is selected and the order of the labels should <br>
not matter.<br>
<br>
<br>
Regards,<br>
August<br>
--<br>
Oberon@lists.inf.ethz.ch mailing list for ETH Oberon and related systems<br>
<a href="https://lists.inf.ethz.ch/mailman/listinfo/oberon">https://lists.inf.ethz.ch/mailman/listinfo/oberon</a><o:p></o:p></span></p>
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