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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-NZ link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:12.0pt;color:#1F497D'>So it’s best to reduce the set size as much as possible. Looking at my code, I have some variables declared as Word (16-bit) with 65535 possible values but most are Byte.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;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";color:windowtext'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'> delphi-bounces@listserver.123.net.nz [mailto:delphi-bounces@listserver.123.net.nz] <b>On Behalf Of </b>Peter Ingham<br><b>Sent:</b> Wednesday, 8 June 2016 8:15 p.m.<br><b>To:</b> delphi@listserver.123.net.nz<br><b>Subject:</b> Re: [DUG] In [set] efficiency<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>(From memory & without firing up a compiler to verify) ...<br><br>Sets are implemented as bitmaps with one bit allocated to each possible value of the set type (hence the limitations on the number of possible elements in the set).<br><br>So if you have<br>type bytesset = [0..7]; // 8 possible values<br>var a: bytesset ;<br>begin<br> if a in [1,4] then<br><br>The set literal [1,4] ends up as a byte with the value $0A.<br>The test "a in [1,4]" is equivalent to "(a AND $0A) <> 0".<br><br>The generated code (for a set of this size) is an AND followed by a conditional jump. Very efficient.<br><br>It gets a little nastier when the possible values gets larger as the size of the set grows (set of AnsiChar is 32 bytes; Set of Widechar exceeds the permissible size of a set).<br><br>The precise code generated by case varies between jump tables and linear comparisons.<br><br>Regards<br> <br><br>On 8/06/2016 5:27 p.m., Steve Peacocke wrote:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal>If I remember correctly, the compiler changes both to array anyway so you come out with exactly the same compiled code. <o:p></o:p></p></div><div id=AppleMailSignature><p class=MsoNormal><o:p> </o:p></p></div><div id=AppleMailSignature><p class=MsoNormal>Perhaps someone can confirm this or tell me how wrong I am?<br><br>Steve Peacocke <o:p></o:p></p><div><p class=MsoNormal>+64 220 612-611<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div></div><div><p class=MsoNormal style='margin-bottom:12.0pt'><br>On 8/06/2016, at 4:56 PM, Ross Levis <<a href="mailto:ross@stationplaylist.com">ross@stationplaylist.com</a>> wrote:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal><span style='font-size:12.0pt;color:#1F497D'>I’m wondering which is more efficient to process...</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;color:#1F497D'> </span><o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;color:#1F497D'>if (a=1) or (a=2) then ...</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;color:#1F497D'> </span><o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;color:#1F497D'>or</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;color:#1F497D'> </span><o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;color:#1F497D'>if a in [1,2] then ...</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;color:#1F497D'> </span><o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;color:#1F497D'>If the answer is the first method, does it make a difference if more numbers are checked, eg. if a in [1..3,5] then</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;color:#1F497D'> </span><o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;color:#1F497D'>Cheers.</span><o:p></o:p></p></div></blockquote><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>_______________________________________________<br>NZ Borland Developers Group - Delphi mailing list<br>Post: <a href="mailto:delphi@listserver.123.net.nz">delphi@listserver.123.net.nz</a><br>Admin: <a href="http://delphi.org.nz/mailman/listinfo/delphi">http://delphi.org.nz/mailman/listinfo/delphi</a><br>Unsubscribe: send an email to <a href="mailto:delphi-request@listserver.123.net.nz">delphi-request@listserver.123.net.nz</a> with Subject: unsubscribe<o:p></o:p></span></p></div></blockquote><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><br><br><br><o:p></o:p></span></p><pre>_______________________________________________<o:p></o:p></pre><pre>NZ Borland Developers Group - Delphi mailing list<o:p></o:p></pre><pre>Post: <a href="mailto:delphi@listserver.123.net.nz">delphi@listserver.123.net.nz</a><o:p></o:p></pre><pre>Admin: <a href="http://delphi.org.nz/mailman/listinfo/delphi">http://delphi.org.nz/mailman/listinfo/delphi</a><o:p></o:p></pre><pre>Unsubscribe: send an email to <a href="mailto:delphi-request@listserver.123.net.nz">delphi-request@listserver.123.net.nz</a> with Subject: unsubscribe<o:p></o:p></pre></blockquote><p><o:p> </o:p></p></div></body></html>