combining boolean conditions with parenthesis

This is a discussion on combining boolean conditions with parenthesis within the C Programming forums, part of the General Programming Boards category; Hello, I was wondering whether the expected parenthesis hierarchy is respected when combining boolean conditions in a do-while loop. To ...

  1. #1
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    combining boolean conditions with parenthesis

    Hello,

    I was wondering whether the expected parenthesis hierarchy is respected when combining boolean conditions in a do-while loop.

    To be concrete, consider this:
    Code:
    do
    {
    ...
    }
    while ( A && ( B || C || D ) )
    Then, the loop terminates when either A is false or (B||C||D) is false, and for this last one to be false, then B and C and D have to be false.

    Am I right? If so, this works in both C and C++?

    Thanks for your help,

    mc61




    Thanks for your help,

    mc61

  2. #2
    Kernel hacker
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    Jul 2007
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    Farncombe, Surrey, England
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    It terminates if either A is false on it's own or B, C and D are all false.

    Note that A is tested first, and if it's FALSE, no other test has to be performed, and you can rely on this in the compiler (for example you can do
    Code:
    if (p != NULL && *p != 7)  ...
    and you can be sure that *p is never being accessed if p is NULL.

    And yes, it's the same in C and C++.

    --
    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.

  3. #3
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    Thanks matsp!

    mc61

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