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  4. [SOLVED] "Round" double
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[SOLVED] "Round" double

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  • B Offline
    B Offline
    beowulf
    wrote on last edited by
    #3

    It's returning "52.5", i want to return "52.4".

    Understand?

    Thanks.

    -- 0x00

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    • L Offline
      L Offline
      leon.anavi
      wrote on last edited by
      #4

      [quote author="l3e0wulf" date="1362577800"]It's returning "52.5", i want to return "52.4".

      Understand?

      Thanks.[/quote]

      I don't know a built-in method that will return you this results but you can easily write your own method. Covert the double to string and remove the unnecessary digits from its end.

      http://anavi.org/

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      • C Offline
        C Offline
        Code_ReaQtor
        wrote on last edited by
        #5

        [quote author="l3e0wulf" date="1362577800"]It's returning "52.5", i want to return "52.4".

        Understand?

        Thanks.[/quote]

        What I can say is that the principle of "Rounding" won't apply here.

        Maybe you can convert your number to QString using QString::number() then use QRegExp rx("(\d+.\d)") or something similar.

        Please visit my open-source projects at https://github.com/Code-ReaQtor.

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        • B Offline
          B Offline
          beowulf
          wrote on last edited by
          #6

          Look my problem.

          I have two double.

          One: 52.48
          Two: 52.4

          I want to know when the "Two - 52.4" number is like the "One - 52.48", and I realised the "One" is always one number different! The last number.

          When I put QString::number("52.48", 'f', 1); it's return 52.5 and in "52.4". It's return: "52.4".

          -- 0x00

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          • C Offline
            C Offline
            Code_ReaQtor
            wrote on last edited by
            #7

            [quote author="l3e0wulf" date="1362579716"]
            When I put QString::number("52.48", 'f', 1); it's return 52.5 and in "52.4". It's return: "52.4".[/quote]

            Because you need to put "2" in the third parameter. Then remove the last number at the end.
            @ QString::number("52.48", 'f', 2);@

            The third parameter is the "precision", using 3 or more will automatically append 0's, AFAIK.
            @ QString::number("52.48", 'f', 4); //it will result to "52.4800"@

            Please visit my open-source projects at https://github.com/Code-ReaQtor.

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            • B Offline
              B Offline
              BelenMuñoz
              wrote on last edited by
              #8

              I think one of the problems is that 52.48 is never like 52.4, if you round it, it's (always) 52.5, so I don't think you'll find a way to solve your problem using numeric types.
              I agree with Leon and Core_ReaQtor you can use QString to transform your number, first passing double to QString, transforming it and then passing it to double again.
              It's a little "cutre" as we say in Spain (I think it's stingy in english), but I don't have a better idea.

              Regards!!

              Me casé con un enano pa jartarme de reí.

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              • B Offline
                B Offline
                beowulf
                wrote on last edited by
                #9

                When i put QString::number("52.4", 'f', 2); i'ts return: "52.40"
                When i put QString::number("52.48", 'f', 2); i'ts return: "52.48"

                When i put QString::number("52.4", 'f', 1); i'ts return: "52.4"
                When i put QString::number("52.48", 'f', 1); i'ts return: "52.5"

                When i put QString::number("52.4", 'f', 2); i'ts return: "52.40"
                When i put QString::number("52.48", 'f', 1); i'ts return: "52.5"

                When i put QString::number("52.4", 'f', 1); i'ts return: "52.4"
                When i put QString::number("52.48", 'f', 2); i'ts return: "52.48"

                -- 0x00

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                • B Offline
                  B Offline
                  beowulf
                  wrote on last edited by
                  #10

                  BelenMuñoz:

                  bq. I agree with Leon and Core_ReaQtor you can use QString to transform your number, first passing double to QString, transforming it and then passing it to double again.

                  I'll try.

                  -- 0x00

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                  • B Offline
                    B Offline
                    beowulf
                    wrote on last edited by
                    #11

                    I used QString::mid!

                    @qDebug() << QString::number(52.48).mid(QString::number(52.48).length() - 1, QString::number(52.48).length());@

                    And it's return the last number.

                    -- 0x00

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                    • B Offline
                      B Offline
                      beowulf
                      wrote on last edited by
                      #12

                      Update

                      Maybe a little big, but that's the solution:

                      @qDebug() << QString::number(52.48).replace(QString::number(52.48).mid(QString::number(52.48).length() - 1, QString::number(52.48).length()), "");@

                      -- 0x00

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                      • B Offline
                        B Offline
                        beowulf
                        wrote on last edited by
                        #13

                        Keep don't working.

                        The problem now is: 52.48 now is 5.4 with:

                        qDebug() << QString::number(52.48).replace(QString::number(52.48).mid(QString::number(52.48).length() - 1, QString::number(52.48).length()), "");

                        -- 0x00

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                        • J Offline
                          J Offline
                          Jake007
                          wrote on last edited by
                          #14

                          Hi!

                          Why are you converting to string?

                          Multiply both numbers by the number of decimals and cast to int.
                          So
                          @auto a = (int)(52.4 * 10) // 524
                          auto b = (int)(52.48 * 10) // 524

                          if( a == b) // means that 52.4 equals 52.48
                          ...
                          @

                          Further on, you can replace * 10 with pow(10, decimalPlaces) to have decimal place comparison dynamical.

                          If you want it back written as 52.4, just divide it by 10.

                          Regards,
                          Jake


                          Code is poetry

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                          • B Offline
                            B Offline
                            beowulf
                            wrote on last edited by
                            #15

                            Wow, wow, wow, Thank you very much Jake007!

                            -- 0x00

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                            • J Offline
                              J Offline
                              Jake007
                              wrote on last edited by
                              #16

                              You're welcome :) .
                              Don't forget to mark thread as solved.
                              And next time you're dealing only with numbers, please leave strings out of it.
                              Your processor will be grateful :)

                              Regards,
                              Jake


                              Code is poetry

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