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Logic

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  • F Fabio V Silva

    I just got an answer[^] downvoted in Q&A because I used & instead of && in this line:

    if(UsernameTextBox.Text == "Manager" & PasswordTextBox.Text == "Maintenance")

    I'm still waiting for a response to my "Why?"

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    Timothy Byrd
    wrote on last edited by
    #45

    So if I have this straight, in your example:

    if(UsernameTextBox.Text == "Manager" & PasswordTextBox.Text == "Maintenance")

    because both arguments are boolean, the '&' is effectively acting just like a '&&' except for being trivially less efficient because it is always doing both of the string compares. I know in this case you were merely quoting previous post using '&', but even if the non-short-circuit behaviour would be useful sometime, I'd avoid it because it just looks wrong to me. We're in a mixed C++/C# environment here, and I have to be on the lookout for misused '&'s in the code as it is. Allowing for false positives is not in the cards here. That said, I think you got a raw deal.

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    • F Fabio V Silva

      I just got an answer[^] downvoted in Q&A because I used & instead of && in this line:

      if(UsernameTextBox.Text == "Manager" & PasswordTextBox.Text == "Maintenance")

      I'm still waiting for a response to my "Why?"

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      R Offline
      Rob Grainger
      wrote on last edited by
      #46

      And quite rightly so. While for booleans, & can work as a logical operator, in all other cases it is bitwise. For consistency, use a single operatopr to represent logical operators throughout, the C# designers (C really) chose && for this purpose. It may work, but its obfuscated, and should be rejected or corrected by any reasonable code review, regardless of any appeals you make to technical documentation.

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      • R Rob Grainger

        And quite rightly so. While for booleans, & can work as a logical operator, in all other cases it is bitwise. For consistency, use a single operatopr to represent logical operators throughout, the C# designers (C really) chose && for this purpose. It may work, but its obfuscated, and should be rejected or corrected by any reasonable code review, regardless of any appeals you make to technical documentation.

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        Timothy Byrd
        wrote on last edited by
        #47

        Rob, I think the problem is that you are assuming human beings are rational/reasonable. Where I am currently, I have to fill out a form and get authorization to fix a simple memory leak. The code base is several million lines of C++, suffering from 20 years of technical debt. Since I already have a reputation for being "too critical about code quality" which causes my input to get knocked down a level or two, I have to bite my tongue a lot. It's a grand learning experience, but I'll be glad when I figure out what the lesson is!

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        • T Timothy Byrd

          Rob, I think the problem is that you are assuming human beings are rational/reasonable. Where I am currently, I have to fill out a form and get authorization to fix a simple memory leak. The code base is several million lines of C++, suffering from 20 years of technical debt. Since I already have a reputation for being "too critical about code quality" which causes my input to get knocked down a level or two, I have to bite my tongue a lot. It's a grand learning experience, but I'll be glad when I figure out what the lesson is!

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          F Offline
          Firo Atrum Ventus
          wrote on last edited by
          #48

          The lesson : Never start a fight in the Hall of Shame :laugh:

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          • F Fabio V Silva

            You're wrong, they don't always short circuit. See here[^] and here[^]. If you're working as C# developer I think you should RTFM.

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            H Offline
            hairy_hats
            wrote on last edited by
            #49

            Fabio V Silva wrote:

            If you're working as C# developer I think you should RTFM.

            No need to be impolite.

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            • F Fabio V Silva

              Again, you're wrong, they are both logical operators in that case but one is short-circuited and the other is not! You have the same think in VB with the And, AndAlso, Or, OrElse operators, they are all handy in different situations.

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              Lost User
              wrote on last edited by
              #50

              'AND' in VB is not equivalent to '&' in C#, but equivalent '&&'. this is applicable for OR also... Only difference is 'AND' is not short circuited where '&&' is short circuited. To achieve short circuited and VB require explicit usage of 'AND ALSO'

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              • L Lost User

                'AND' in VB is not equivalent to '&' in C#, but equivalent '&&'. this is applicable for OR also... Only difference is 'AND' is not short circuited where '&&' is short circuited. To achieve short circuited and VB require explicit usage of 'AND ALSO'

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                agolddog
                wrote on last edited by
                #51

                But nobody here can understand why I continue to suggest we move from VB to C#. Of course we want the default behavior to be as inefficient as possible!

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                • F Fabio V Silva

                  Again, you're wrong, they are both logical operators in that case but one is short-circuited and the other is not! You have the same think in VB with the And, AndAlso, Or, OrElse operators, they are all handy in different situations.

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                  dchrno
                  wrote on last edited by
                  #52

                  In your example it's a waste of CPU cycles not to short circuit using &&. The exception is if you have somehow overloaded the & operator, or have logic in your Text property that needs to be evaluated every time.

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                  • L Lost User

                    It is your mistake that you are using & like a logical operator. It is NOT supposed to be used as a logical operator, we have && for that purpose.

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                    Jason Christian
                    wrote on last edited by
                    #53

                    http://msdn.microsoft.com/en-us/library/aa691306%28v=vs.71%29.aspx[^] This (from Microsoft) includes & and | in the logical operators. And semantics aside, they can and sometimes should be used as such in C# - for those cases where you want a logical operator without short-circuiting (i.e. one of the operands is a method call with side-effects - which would be a whole nother type of questionable practice, but the language allows it and it has is uses). So in that sense the OP is correct, & and && do the same thing except && short-circuits. Of course, they don't do exactly the same thing, because & can also be used on non-boolean types as a bitwise operator. So (4 & 5) is meaningful, whereas 4 && 5 is not.

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                    • B BobJanova

                      Indeed. & and | on ints (or uints) is very useful.

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                      L Offline
                      Lost User
                      wrote on last edited by
                      #54

                      Absolutely, because && and || wouldn't work with ints (and uints).

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                      • F Fabio V Silva

                        I just got an answer[^] downvoted in Q&A because I used & instead of && in this line:

                        if(UsernameTextBox.Text == "Manager" & PasswordTextBox.Text == "Maintenance")

                        I'm still waiting for a response to my "Why?"

                        J Offline
                        J Offline
                        James Lonero
                        wrote on last edited by
                        #55

                        The "answer" person's assumptions doesn't seem to match with what you have in your message. Using & is different than using && and the results could be different, depending on what you are comparing. Since both return either true of false, there will not be a difference in the result. (The only difference is how the result is achieved.) In C and C++, you can "AND items that are not boolean as: int i, j; i = 1; j = 2; if (i and j) --> result is false (bitwise AND: 1 & 2 yields 0 or false). if (i and j) --> result is true (logical AND: 1 && 2 yields non-zero or true). Hope this helps.

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                        • F Fabio V Silva

                          You're wrong, they don't always short circuit. See here[^] and here[^]. If you're working as C# developer I think you should RTFM.

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                          Mel Padden
                          wrote on last edited by
                          #56

                          Fabio V Silva wrote:

                          If you're working as C# developer I think you should RTFM.

                          You, sir, are a disgrace. Not only are you inaccurate in your assertions, you display the two traits I detest most about *some* people who work in this profession - a lack of respect for those around you, and a blinkered solipsism bordering on egomania. Wise the f**k up son. Nobody's impressed.

                          Smokie, this is not 'Nam. This is bowling. There are rules. www.geticeberg.com http://melpadden.wordpress.com

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