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  4. problems on using the if and else statement and updating the data.
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problems on using the if and else statement and updating the data.

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c++ qtupdateif and else
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  • sierdzioS sierdzio

    Do you actually want to ask some question here? What is your problem?

    Do you mean to ask how to check multiple values at once in an if statement?

    ui-> (AddOn1 + AddOn2 + AddOn3) -> isChecked()

    Here is something which should work:

    if (ui->AddOn1->isChecked() && ui->AddOn2->isChecked() && ui->AddOn3->isChecked())
    

    But for sake of readability and maintenance (and, to some degree, performance), I'd suggest to get state first, and check later:

    const bool isAddOn1 = ui->AddOn1->isChecked();
    const bool isAddOn2 = ui->AddOn2->isChecked();
    const bool isAddOn3 = ui->AddOn3->isChecked();
    if (isAddOn1 && isAddOn2 && isAddOn3)
    // ...
    

    All modernt compilers also understand and as a synonym to && so you can do:

    if (isAddOn1 and isAddOn2 and isAddOn3)
    
    JonBJ Offline
    JonBJ Offline
    JonB
    wrote on last edited by JonB
    #8

    @sierdzio said in problems on using the if and else statement and updating the data.:

    All modernt compilers also understand and as a synonym to && so you can do:

    I am speechless! Apart from the fact that I have never heard of this (old time C/C++ programmer, now returned to new C++). And apart from the fact that introducing and as a language keyword would potentially break one million old C/C++ programs which could have used and as a variable?

    You are obviously more expert than I, but do you want to recommend this to a newbie? I have never noticed and used in a C++ program, if OP is to produce standard code, and recognize others' code, would you not recommend sticking with &&?

    J.HilkJ 1 Reply Last reply
    0
    • JonBJ JonB

      @sierdzio said in problems on using the if and else statement and updating the data.:

      All modernt compilers also understand and as a synonym to && so you can do:

      I am speechless! Apart from the fact that I have never heard of this (old time C/C++ programmer, now returned to new C++). And apart from the fact that introducing and as a language keyword would potentially break one million old C/C++ programs which could have used and as a variable?

      You are obviously more expert than I, but do you want to recommend this to a newbie? I have never noticed and used in a C++ program, if OP is to produce standard code, and recognize others' code, would you not recommend sticking with &&?

      J.HilkJ Offline
      J.HilkJ Offline
      J.Hilk
      Moderators
      wrote on last edited by
      #9

      @JonB apparently part of the standard since c++98
      https://en.cppreference.com/w/cpp/keyword/and


      Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


      Q: What's that?
      A: It's blue light.
      Q: What does it do?
      A: It turns blue.

      JonBJ 1 Reply Last reply
      2
      • J.HilkJ J.Hilk

        @JonB apparently part of the standard since c++98
        https://en.cppreference.com/w/cpp/keyword/and

        JonBJ Offline
        JonBJ Offline
        JonB
        wrote on last edited by JonB
        #10

        @J-Hilk , @sierdzio
        Absolutely shocking! I see from https://en.cppreference.com/w/cpp/language/operator_alternative that there are actually 11 new reserved words for operators. Including not, and even the string compl, which I might have used as variables and would break upgrading to C++ '98.

        Thinking aloud, I believe all C operators were symbols and not words, part of the charm (for right or for wrong) of the language.

        With all due respect to @sierdzio's comment, which I accept & respect, I have still never seen a piece of C++ code using any of these.... [And hence would caution a beginner against adopting these.]

        [C++ looks like it's trying to be a Python-wannabe ;-) ]

        jsulmJ 1 Reply Last reply
        1
        • JonBJ JonB

          @J-Hilk , @sierdzio
          Absolutely shocking! I see from https://en.cppreference.com/w/cpp/language/operator_alternative that there are actually 11 new reserved words for operators. Including not, and even the string compl, which I might have used as variables and would break upgrading to C++ '98.

          Thinking aloud, I believe all C operators were symbols and not words, part of the charm (for right or for wrong) of the language.

          With all due respect to @sierdzio's comment, which I accept & respect, I have still never seen a piece of C++ code using any of these.... [And hence would caution a beginner against adopting these.]

          [C++ looks like it's trying to be a Python-wannabe ;-) ]

          jsulmJ Offline
          jsulmJ Offline
          jsulm
          Lifetime Qt Champion
          wrote on last edited by
          #11

          @JonB said in problems on using the if and else statement and updating the data.:

          I have still never seen a piece of C++ code using any of these

          Me neither :-)

          https://forum.qt.io/topic/113070/qt-code-of-conduct

          1 Reply Last reply
          2
          • sierdzioS Offline
            sierdzioS Offline
            sierdzio
            Moderators
            wrote on last edited by
            #12

            I have seen it but very, very rarely.

            And hence would caution a beginner against adopting these

            I'm split on this :D One one hand, && is clearly, vastly, totally the established and well-known convention practically everywhere. So using it is definitely a good idea.

            But on the other hand, and is more readable and convenient. So it is also a good idea.

            (Z(:^

            JonBJ 1 Reply Last reply
            1
            • sierdzioS sierdzio

              I have seen it but very, very rarely.

              And hence would caution a beginner against adopting these

              I'm split on this :D One one hand, && is clearly, vastly, totally the established and well-known convention practically everywhere. So using it is definitely a good idea.

              But on the other hand, and is more readable and convenient. So it is also a good idea.

              JonBJ Offline
              JonBJ Offline
              JonB
              wrote on last edited by JonB
              #13

              @sierdzio said in problems on using the if and else statement and updating the data.:

              But on the other hand, and is more readable and convenient.

              In Pascal or Python, yes. When scanning C/C++ I expect to see all operators as symbols (and not some but not others) Next C++ will be offering begin/end for {/}! [Some people used to do all this words-for-symbols via C #defines.] I give up on the modern world, it's all going to pot... ;-)

              J.HilkJ 1 Reply Last reply
              1
              • JonBJ JonB

                @sierdzio said in problems on using the if and else statement and updating the data.:

                But on the other hand, and is more readable and convenient.

                In Pascal or Python, yes. When scanning C/C++ I expect to see all operators as symbols (and not some but not others) Next C++ will be offering begin/end for {/}! [Some people used to do all this words-for-symbols via C #defines.] I give up on the modern world, it's all going to pot... ;-)

                J.HilkJ Offline
                J.HilkJ Offline
                J.Hilk
                Moderators
                wrote on last edited by
                #14

                @JonB said in problems on using the if and else statement and updating the data.:

                Next C++ will be offering begin/end for {/}!

                you can use

                {	??<
                }	??>
                [	??(
                ]	??)
                #	??=
                \	??/
                ^	??'
                |	??!
                ~	??-
                

                but that was removed in c++17, :)


                Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                Q: What's that?
                A: It's blue light.
                Q: What does it do?
                A: It turns blue.

                JonBJ 1 Reply Last reply
                1
                • J.HilkJ J.Hilk

                  @JonB said in problems on using the if and else statement and updating the data.:

                  Next C++ will be offering begin/end for {/}!

                  you can use

                  {	??<
                  }	??>
                  [	??(
                  ]	??)
                  #	??=
                  \	??/
                  ^	??'
                  |	??!
                  ~	??-
                  

                  but that was removed in c++17, :)

                  JonBJ Offline
                  JonBJ Offline
                  JonB
                  wrote on last edited by JonB
                  #15

                  @J-Hilk

                  but that was removed in c++17, :)

                  Even better --- you start using new language constructs and then they remove them so that your code gets broken!

                  FWIW, I note from https://en.cppreference.com/w/cpp/language/operator_alternative

                  There are alternative spellings for several operators and other tokens that use non-ISO646 characters.

                  So the motivation never was "clarity", it's to do with people having funny keyboards....

                  1 Reply Last reply
                  1
                  • SGaistS Offline
                    SGaistS Offline
                    SGaist
                    Lifetime Qt Champion
                    wrote on last edited by
                    #16

                    @JonB said in problems on using the if and else statement and updating the data.:

                    funny keyboards

                    The hardware is innocent ;-P

                    Interested in AI ? www.idiap.ch
                    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                    1 Reply Last reply
                    0
                    • Kent-DorfmanK Offline
                      Kent-DorfmanK Offline
                      Kent-Dorfman
                      wrote on last edited by
                      #17

                      whats next, espousing the virtues of trigraphs?

                      1 Reply Last reply
                      0
                      • 1 Offline
                        1 Offline
                        1Manui1
                        wrote on last edited by
                        #18

                        How did you do it now?

                        1 Reply Last reply
                        0

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