library question max(val, 255)

This is a discussion on library question max(val, 255) within the C++ Programming forums, part of the General Programming Boards category; I've got this code 'snippet' that is giving me problems. Isn't max(val, 255) part of the <iostream> library? I get ...

  1. #1
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    library question max(val, 255)

    I've got this code 'snippet' that is giving me problems. Isn't max(val, 255) part of the <iostream> library? I get an error when I use it like this:

    Code:
    val=max(min(val,0),255);
    Says that 'max' : undeclared identifier ... and
    'min' : undeclared identifier

    I've been looking at libraries to see if there is another I am supposed to include, but I haven't found anything helpful.

    tms

  2. #2
    C++ Witch laserlight's Avatar
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    Isn't max(val, 255) part of the <iostream> library?
    No, std::max and std::min are from <algorithm>
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    OK, so I just added #include <algorithm> and I am still getting this error message....

  4. #4
    C++ Witch laserlight's Avatar
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    Show the smallest and simplest program that demonstrates the error.

    EDIT:
    By the way, I think std::max(std::min(val, 0), 255) will always return 255.
    Last edited by laserlight; 09-09-2007 at 10:30 AM.
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  5. #5
    Technical Lead QuantumPete's Avatar
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    Not a hundred percent sure here, but shouldn't you use std::max instead of just max? Or have you included the std namespace?

    QuantumPete
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    There is an error with VC++ 6.0 and maybe some other compilers and versions where max and min are #define'd symbols. That means they override any max and min function from <algorithm>. There is something you can define in your program so that it will work. It might be
    Code:
    #define NO_MIN_MAX
    above your includes, but I'm not sure on the details. If that doesn't work then your compiler and version would be helpful to know.

    Also, using std::max and std::min, even if you have a using namespace std in your code, can prevent name conflicts with other usages of max and min (that aren't #define symbols).

  7. #7
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    Quote Originally Posted by laserlight View Post
    EDIT:
    By the way, I think std::max(std::min(val, 0), 255) will always return 255.
    Will it do so if val is of type signed char?
    There are 10 types of people in this world, those who cringed when reading the beginning of this sentence and those who salivated to how superior they are for understanding something as simple as binary.

  8. #8
    C++ Witch laserlight's Avatar
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    Will it do so if val is of type signed char?
    It may not even compile due to mismatch of template parameter and arguments. My assumption is that val is of type int, but it may not be, which is why tms43 should have posted an example program.
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