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Boolean in C

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  • sierdzioS Offline
    sierdzioS Offline
    sierdzio
    Moderators
    wrote on last edited by
    #7

    Good point :D Corrected

    (Z(:^

    1 Reply Last reply
    0
    • SaintBrosephS SaintBroseph

      Yes Yes! I actually wanted an example of a C boolean using typedef keyword.

      DarkChocolateMuffinzD Offline
      DarkChocolateMuffinzD Offline
      DarkChocolateMuffinz
      wrote on last edited by JKSH
      #8

      @SaintBroseph Here's an example (code) of C boolean using typedef

      #include <stdio.h>
      
      // creating custom data type bool
      typedef enum {false, true} bool_enum;
      int main() {
          bool_enum x=false; // declaration and initialization  
          if(x==true)  // conditional statements    
              printf("The value of x is true");  
          else  
              printf("The value of x is false");
        
          return 0;  
          // Output: The value of x is false
      }
      

      Source: [EDIT: Link removed --JKSH]

      1 Reply Last reply
      1
      • Ketan__Patel__0011K Offline
        Ketan__Patel__0011K Offline
        Ketan__Patel__0011
        wrote on last edited by Ketan__Patel__0011
        #9
        typedef bool boolean;
        int main()
        {
             boolean A = false;
             if (A == false) printf("MESSAGE")
             else  printf("MESSAGE")
        
             return 0;
        }
        

        if your problem is solved then please close the thread

        1 Reply Last reply
        0
        • Kent-DorfmanK Offline
          Kent-DorfmanK Offline
          Kent-Dorfman
          wrote on last edited by
          #10

          comparing a boolean to true or false is redundant. Conditional expressions return a boolean (in C, 0 or not 0) so X or !X is adequate.

          Also, bool is a C99 thing via <stdbool.h>. Much C legacy still exists where there is no real boolean type but instead zero or not zero logic.

          kshegunovK 1 Reply Last reply
          2
          • Kent-DorfmanK Kent-Dorfman

            comparing a boolean to true or false is redundant. Conditional expressions return a boolean (in C, 0 or not 0) so X or !X is adequate.

            Also, bool is a C99 thing via <stdbool.h>. Much C legacy still exists where there is no real boolean type but instead zero or not zero logic.

            kshegunovK Offline
            kshegunovK Offline
            kshegunov
            Moderators
            wrote on last edited by
            #11

            @Kent-Dorfman said in Boolean in C:

            comparing a boolean to true or false is redundant.

            Not to mention wrong, generally speaking. 1 evaluates to true but so does -1, so comparing against true is simply the way to break it. Enums implicitly decay to the underlying type so checking against condition and !condition is the correct way to do it, even if a typedef is used.

            Read and abide by the Qt Code of Conduct

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

              I find it much easier to understand if something is false when I see if (something == false) than when I see if (!something). Especially in longer expressions it is very easy to miss a single character like ! and read the code wrong.

              (Z(:^

              JonBJ J.HilkJ 2 Replies Last reply
              2
              • sierdzioS sierdzio

                I find it much easier to understand if something is false when I see if (something == false) than when I see if (!something). Especially in longer expressions it is very easy to miss a single character like ! and read the code wrong.

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

                @sierdzio
                I see a personal-choice-disagreement debate looming... ;-)

                I do agree it is "unfortunate" that C chose just that little ! for "not". But personally I never write == false or != false, because I would never "say" that in RL....

                1 Reply Last reply
                0
                • sierdzioS sierdzio

                  I find it much easier to understand if something is false when I see if (something == false) than when I see if (!something). Especially in longer expressions it is very easy to miss a single character like ! and read the code wrong.

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

                  @sierdzio , @JonB

                  are you guys aware, that not is a valid keyword in c++ ?

                  https://en.cppreference.com/w/cpp/keyword/not


                  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 sierdzioS Kent-DorfmanK 3 Replies Last reply
                  1
                  • J.HilkJ J.Hilk

                    @sierdzio , @JonB

                    are you guys aware, that not is a valid keyword in c++ ?

                    https://en.cppreference.com/w/cpp/keyword/not

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

                    @J-Hilk
                    Yup. And it's devil's-spawn! ;-) [Same for and & or. If I wanted to program in Python or Pascal I would have picked that.] I would never use that, as "nobody" (most people) else uses it or knows about it, so I would regard it as an anti-pattern!

                    1 Reply Last reply
                    0
                    • J.HilkJ J.Hilk

                      @sierdzio , @JonB

                      are you guys aware, that not is a valid keyword in c++ ?

                      https://en.cppreference.com/w/cpp/keyword/not

                      sierdzioS Offline
                      sierdzioS Offline
                      sierdzio
                      Moderators
                      wrote on last edited by
                      #16

                      @J-Hilk said in Boolean in C:

                      @sierdzio , @JonB

                      are you guys aware, that not is a valid keyword in c++ ?

                      https://en.cppreference.com/w/cpp/keyword/not

                      Yes but not in all compilers :-( MSVC does not recognize it.

                      (Z(:^

                      JonBJ J.HilkJ 2 Replies Last reply
                      1
                      • sierdzioS sierdzio

                        @J-Hilk said in Boolean in C:

                        @sierdzio , @JonB

                        are you guys aware, that not is a valid keyword in c++ ?

                        https://en.cppreference.com/w/cpp/keyword/not

                        Yes but not in all compilers :-( MSVC does not recognize it.

                        JonBJ Offline
                        JonBJ Offline
                        JonB
                        wrote on last edited by
                        #17

                        @sierdzio
                        Good, but are you sure? Since it is valid since C99, I would have thought that MSVC would accept those?

                        sierdzioS 1 Reply Last reply
                        0
                        • JonBJ JonB

                          @sierdzio
                          Good, but are you sure? Since it is valid since C99, I would have thought that MSVC would accept those?

                          sierdzioS Offline
                          sierdzioS Offline
                          sierdzio
                          Moderators
                          wrote on last edited by
                          #18

                          @JonB said in Boolean in C:

                          @sierdzio
                          Good, but are you sure? Since it is valid since C99, I would have thought that MSVC would accept those?

                          Last time I tried was last year. Clang, GCC all are 100% fine with it, MSVC was throwing errors.

                          I now see it's supposed to be defined in some iso646.h header, I never included it, perhaps that's the reason.

                          (Z(:^

                          JonBJ 1 Reply Last reply
                          1
                          • sierdzioS sierdzio

                            @J-Hilk said in Boolean in C:

                            @sierdzio , @JonB

                            are you guys aware, that not is a valid keyword in c++ ?

                            https://en.cppreference.com/w/cpp/keyword/not

                            Yes but not in all compilers :-( MSVC does not recognize it.

                            J.HilkJ Offline
                            J.HilkJ Offline
                            J.Hilk
                            Moderators
                            wrote on last edited by
                            #19

                            @sierdzio said in Boolean in C:

                            Yes but not in all compilers :-( MSVC does not recognize it.

                            VS been nonconforming! 😱 Color me surprised 😉


                            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.

                            1 Reply Last reply
                            1
                            • sierdzioS sierdzio

                              @JonB said in Boolean in C:

                              @sierdzio
                              Good, but are you sure? Since it is valid since C99, I would have thought that MSVC would accept those?

                              Last time I tried was last year. Clang, GCC all are 100% fine with it, MSVC was throwing errors.

                              I now see it's supposed to be defined in some iso646.h header, I never included it, perhaps that's the reason.

                              JonBJ Offline
                              JonBJ Offline
                              JonB
                              wrote on last edited by
                              #20

                              @sierdzio
                              If one has to include a header file for them, makes me wonder if they are not "part of the language", just should be available if you include the header. Are they just #defines in that file??

                              sierdzioS 1 Reply Last reply
                              1
                              • JonBJ JonB

                                @sierdzio
                                If one has to include a header file for them, makes me wonder if they are not "part of the language", just should be available if you include the header. Are they just #defines in that file??

                                sierdzioS Offline
                                sierdzioS Offline
                                sierdzio
                                Moderators
                                wrote on last edited by
                                #21

                                @JonB said in Boolean in C:

                                @sierdzio
                                If one has to include a header file for them, makes me wonder if they are not "part of the language", just should be available if you include the header. Are they just #defines in that file??

                                yup :D

                                #define and    &&
                                #define and_eq &=
                                #define bitand &
                                #define bitor  |
                                #define compl  ~
                                #define not    !
                                #define not_eq !=
                                #define or     ||
                                #define or_eq  |=
                                #define xor    ^
                                #define xor_eq ^=
                                

                                They are not actual C++ language reserved keywords.

                                (Z(:^

                                JonBJ 1 Reply Last reply
                                1
                                • sierdzioS sierdzio

                                  @JonB said in Boolean in C:

                                  @sierdzio
                                  If one has to include a header file for them, makes me wonder if they are not "part of the language", just should be available if you include the header. Are they just #defines in that file??

                                  yup :D

                                  #define and    &&
                                  #define and_eq &=
                                  #define bitand &
                                  #define bitor  |
                                  #define compl  ~
                                  #define not    !
                                  #define not_eq !=
                                  #define or     ||
                                  #define or_eq  |=
                                  #define xor    ^
                                  #define xor_eq ^=
                                  

                                  They are not actual C++ language reserved keywords.

                                  JonBJ Offline
                                  JonBJ Offline
                                  JonB
                                  wrote on last edited by
                                  #22

                                  @sierdzio
                                  Hmmmm.... So does gcc have these in some header file, or does their C++ actually have them as reserved? It does have an iso646.h file, with the #defines, yet you said they worked for you in gcc without you explicitly including that? Does it include it automatically or from something else?

                                  J.HilkJ 1 Reply Last reply
                                  1
                                  • JonBJ JonB

                                    @sierdzio
                                    Hmmmm.... So does gcc have these in some header file, or does their C++ actually have them as reserved? It does have an iso646.h file, with the #defines, yet you said they worked for you in gcc without you explicitly including that? Does it include it automatically or from something else?

                                    J.HilkJ Offline
                                    J.HilkJ Offline
                                    J.Hilk
                                    Moderators
                                    wrote on last edited by
                                    #23

                                    @JonB said in Boolean in C:

                                    worked for you in gcc without you explicitly including that? Does it include it automatically or from something else

                                    This header was originally in the C standard library as <iso646.h>.
                                    Compatibility header, in C defines alternative operator representations which are keywords in C++.
                                    This means that in a conforming implementation, including this header has no effect.
                                    

                                    gcc has mostly a conforming implementation, at least in this regard


                                    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 said in Boolean in C:

                                      worked for you in gcc without you explicitly including that? Does it include it automatically or from something else

                                      This header was originally in the C standard library as <iso646.h>.
                                      Compatibility header, in C defines alternative operator representations which are keywords in C++.
                                      This means that in a conforming implementation, including this header has no effect.
                                      

                                      gcc has mostly a conforming implementation, at least in this regard

                                      JonBJ Offline
                                      JonBJ Offline
                                      JonB
                                      wrote on last edited by
                                      #24

                                      @J-Hilk said in Boolean in C:

                                      This header was originally in the C standard library as <iso646.h>.

                                      So what file is this in, which you say is included automatically?

                                      jsulmJ J.HilkJ 2 Replies Last reply
                                      0
                                      • JonBJ JonB

                                        @J-Hilk said in Boolean in C:

                                        This header was originally in the C standard library as <iso646.h>.

                                        So what file is this in, which you say is included automatically?

                                        jsulmJ Offline
                                        jsulmJ Offline
                                        jsulm
                                        Lifetime Qt Champion
                                        wrote on last edited by
                                        #25

                                        @JonB said in Boolean in C:

                                        which you say is included automatically?

                                        My understanding is that it is NOT included automatically in conforming C++ implementations because those understand these words as keywords and don't need this header file (which is only there for compatibility reasons).

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

                                        JonBJ 1 Reply Last reply
                                        2
                                        • JonBJ JonB

                                          @J-Hilk said in Boolean in C:

                                          This header was originally in the C standard library as <iso646.h>.

                                          So what file is this in, which you say is included automatically?

                                          J.HilkJ Offline
                                          J.HilkJ Offline
                                          J.Hilk
                                          Moderators
                                          wrote on last edited by
                                          #26

                                          @JonB I'm talking about the iso646.h @sierdzio mentioned

                                          https://en.cppreference.com/w/cpp/header/ciso646

                                          Probably the reason why MSVC doesn't have those as keywords but requires this header is, IIRC, that it doesn't have/use a dedicated c compiler for c headers and it would break legacy stuff if those were used as keywords


                                          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.

                                          1 Reply Last reply
                                          1

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