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Michael Karas
06/01/12 14:30
Read: 645 times
Beaverton Or
USA


 
#187601 - Very Important
Responding to: Andy Peters's previous message
Andy Peters said:
Justin Fontes said:
Per said:
An expression with multiple || will (and must) end evaluation on first true.
An expression with multiple && will (and must) end evaluation on first false.


Completely true. This is called Short-circuit evaluation and details can be found here:

http://en.wikipedia.org/wiki/Shor...evaluation

Pretty good for being able to point to this out, Per.


Excellent, thanks for the clear explanation.

-a


Yes, and this behavior of the C language can and sometimes is used to advantage in certain types of expressions. When you are studying code from someone else or doing design review type work lack of knowledge about how the language handles multi term expressions can be a killer.

Michael Karas

List of 33 messages in thread
TopicAuthorDate
Where can one learn Intermediate C techniques for 8051      David Good      05/22/12 17:42      
   on the right track        Maarten Brock      05/23/12 06:11      
      one more thing      Erik Malund      05/23/12 07:15      
         Not uncommon bid bad coding standards to comply with      Per Westermark      05/23/12 08:14      
         Not afraid of globals, but...      David Good      05/23/12 10:07      
   More keil optimizer interesting tidbits      David Good      05/24/12 16:24      
      optimization      Maarten Brock      05/25/12 05:35      
      nothing gained, nothing lost      Erik Malund      05/25/12 07:53      
         I don't      Per Westermark      05/25/12 07:58      
            you can do both      Erik Malund      05/25/12 09:44      
               That is not helping the compiler      Justin Fontes      05/25/12 16:31      
                  exact same      Maarten Brock      05/26/12 03:36      
                     Technically, they are not the same      Justin Fontes      05/26/12 11:17      
                        Hmmm...      Andy Neil      05/26/12 23:46      
                        C don't do full evaluation of logical expressions      Per Westermark      05/28/12 06:33      
                           In discrete mathematics proving one is not a proof      Justin Fontes      05/28/12 14:02      
                              Lazy evaluation demanded        Per Westermark      05/28/12 14:51      
                                 I have learned something new because of this      Justin Fontes      05/28/12 17:54      
                                    me too      Andy Peters      06/01/12 11:43      
                                       Very Important      Michael Karas      06/01/12 14:30      
                              Breaks.      Michael Karas      05/28/12 17:57      
                                 Compile the code      Justin Fontes      05/28/12 18:28      
                                    To be more exact      Justin Fontes      05/28/12 19:11      
                                       Stop It!!        Michael Karas      05/28/12 22:01      
                                          That is exactly what I intended      Justin Fontes      05/29/12 10:16      
                                             Switch Break.      Michael Karas      05/29/12 22:04      
               obfusciating code to help the compiler is a VERY bad idea      Andy Neil      05/27/12 07:13      
                  the source of this      Erik Malund      05/27/12 07:17      
   Where can one learn Intermediate C techniques for 8051      Andy Neil      05/26/12 23:56      
   Getting the least out of your compiler        Andy Neil      05/27/12 07:25      
      Maybe IAR should follow their own advice?      Christoph Franck      05/30/12 02:05      
         provided the case ...      Maarten Brock      05/30/12 06:29      
            Compilers not knowing the target chip.      Christoph Franck      05/31/12 03:19      

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