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.
From: [email protected] [mailto:[email protected]] On Behalf Of Peter Ingham Sent: Wednesday, 8 June 2016 8:15 p.m. To: [email protected] Subject: Re: [DUG] In [set] efficiency (From memory & without firing up a compiler to verify) ... 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). So if you have type bytesset = [0..7]; // 8 possible values var a: bytesset ; begin if a in [1,4] then The set literal [1,4] ends up as a byte with the value $0A. The test "a in [1,4]" is equivalent to "(a AND $0A) <> 0". The generated code (for a set of this size) is an AND followed by a conditional jump. Very efficient. 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). The precise code generated by case varies between jump tables and linear comparisons. Regards On 8/06/2016 5:27 p.m., Steve Peacocke wrote: If I remember correctly, the compiler changes both to array anyway so you come out with exactly the same compiled code. Perhaps someone can confirm this or tell me how wrong I am? Steve Peacocke +64 220 612-611 On 8/06/2016, at 4:56 PM, Ross Levis <[email protected]> wrote: I'm wondering which is more efficient to process... if (a=1) or (a=2) then ... or if a in [1,2] then ... 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 Cheers. _______________________________________________ NZ Borland Developers Group - Delphi mailing list Post: [email protected] Admin: http://delphi.org.nz/mailman/listinfo/delphi Unsubscribe: send an email to [email protected] with Subject: unsubscribe _______________________________________________ NZ Borland Developers Group - Delphi mailing list Post: [email protected] Admin: http://delphi.org.nz/mailman/listinfo/delphi Unsubscribe: send an email to [email protected] with Subject: unsubscribe
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