quick question regarding the '==' sign.

This is a discussion on quick question regarding the '==' sign. within the C++ Programming forums, part of the General Programming Boards category; can you have a situation like Code: int a = 3; int b = 3; int c = 3; if ...

  1. #1
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    quick question regarding the '==' sign.

    can you have a situation like

    Code:
    int a = 3;
    int b = 3;
    int c = 3;
    
    if (a == b == c){
          cout<< "yes";
    }
    or does it have to be

    Code:
    if (a == b && a == c){
          cout<< "yes";
    }

  2. #2
    C++ Witch laserlight's Avatar
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    It can be the former (but you may get a result which you did not expect), but it should be the latter.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  3. #3
    Kernel hacker
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    The second one will do what you want. The first one does:
    Code:
    a == (b == c)
    Which can be re-written as:
    Code:
    temp = (b == c);  // Makes a value of 0 or 1. (parenthesis not strictly necessary)
    a == temp;
    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  4. #4
    Jack of many languages Dino's Avatar
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    So, to clarify (for myself),
    Code:
    a==b==c ;
    results in false, even through a==b is true and b==c is true. Correct?

    Todd

  5. #5
    C++ Witch laserlight's Avatar
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    results in false, even through a==b is true and b==c is true. Correct?
    Correct, except for special cases, e.g., a = b = c = 1.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

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