bool variables

This is a discussion on bool variables within the C++ Programming forums, part of the General Programming Boards category; I have a vector of bool vals; V1 = [0,1,0,1] V2 = [1,0,0,1] V3 = [1,1,1,1] V4 = [0,0,0,1] V1*V2 ...

  1. #1
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    bool variables

    I have a vector of bool vals;
    V1 = [0,1,0,1]
    V2 = [1,0,0,1]
    V3 = [1,1,1,1]
    V4 = [0,0,0,1]

    V1*V2 = [0,0,0,0]
    V1*V3 = [0,1,0,1]
    V1*V4 = [0,0,0,1]


    what is fastest way to perform the following operation in C++

    if V1*V2 = V1 then true else false?
    if V1*V3 = V1 then true else false?
    if V1*V4 = V1 then true else false?

    is there a way to do it with addition/subtraction instead of multiplication?

    when I do subtraction the -1 val become a true.

  2. #2
    C++ Witch laserlight's Avatar
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    Multiplication can be done by &&. I do not know about faster or slower, but it makes more sense than multiplication where boolean values are concerned. (What does true multiplied by true mean?)
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  3. #3
    C++まいる!Cをこわせ!
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    Do you really have to do this without multiplication? Have you actually seen that it is a bottleneck?
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    Generally, for boolean values, you use AND(&&) for multiplication, and XOR(!=) for addition, assuming the boolean is seen as integers modulo 2.
    It is too clear and so it is hard to see.
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    Quote Originally Posted by Elysia View Post
    Do you really have to do this without multiplication? Have you actually seen that it is a bottleneck?
    I don't even know how to do bottleneck testing, was just wondering if someone had some insight. how can i do that?

  6. #6
    C++まいる!Cをこわせ!
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    If you run your program, does it take long time to execute?
    If yes, then you can use a profiler to find out where most of the time is spent. If the time is spent on your multiplication, then you can optimize it. Otherwise it's called premature optimization and that's never a good thing.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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