[DUG] In [set] efficiency

[John Bird]

I don’t know the compiler for sure on this, but surely has to be that the set option gets compiled like a case statement, which minimises the number of comparisons made.

Speaking of which, I just this week combined this with a case statement – not clearly documented but it does work.  This example is sanitising an ansi/ascii file for non-printing characters

case FileBytes[i] of
10,13:    begin
                //handle end of line
          end;
9,12,32..126:
          begin
                //handle printable characters (9=tab, 12=page break)
          end
else
          begin
                //handle everything else not printable
          end;
end;

(This was to overcome the TStringlist.loadfromfile limitation where large files or files with any binary zeros only partially load.)



From: Ross Levis 
Sent: Wednesday, June 8, 2016 4:56 PM
To: 'NZ Borland Developers Group - Delphi List' 
Subject: [DUG] In [set] efficiency

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: delphi at listserver.123.net.nz
Admin: http://delphi.org.nz/mailman/listinfo/delphi
Unsubscribe: send an email to delphi-request at listserver.123.net.nz with Subject: unsubscribe
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://listserver.123.net.nz/pipermail/delphi/attachments/20160608/5277e2fd/attachment.html