#1,200 – Logical Operators vs. Conditional Logical Operators

You can use either the logical operators (|, &) or the conditional logical operators (||, &&) when comparing two boolean values (or expressions).

            bool isFromMN = true;
            bool likesConfrontation = false;

            bool bResult = likesConfrontation & isFromMN;  // false
            bResult = likesConfrontation && isFromMN;      // false
            bResult = likesConfrontation | isFromMN;       // true
            bResult = likesConfrontation || isFromMN;       // true

The difference between these operators, when used with boolean values, is that the conditional logical operators can short-circuit evaluation, avoiding evaluation of the right side of the expression if possible.

            int val = 0;

            // Short-circuits (right side not evaluated)
            bResult = isFromMN || ((5 / val) == 1);     // true 

            // Throws exception (does not short-circuit)
            bResult = isFromMN | ((5 / val) == 1);
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About Sean
Software developer in the Twin Cities area, passionate about .NET technologies. Equally passionate about my own personal projects related to family history and preservation of family stories and photos.

4 Responses to #1,200 – Logical Operators vs. Conditional Logical Operators

  1. Pingback: Dew Drop – October 9, 2014 (#1873) | Morning Dew

  2. James Curran says:

    I’ve always been amazed by the number of professional programmers I’ve met who don’t understand short-circuit evaluation, despite the fact that it’s identical in C#, C++, Java Javascript and C, and thus has been that way for over 30 years (as part of the C language specification in K&R 1st Ed)

    And what I found truly stunning is many writers (thankfully, not you), assuming it’s just a quirk of a particular compiler and advocating not depending on it!

  3. Rinto Anto says:

    Short-circuiting often help me to avoid executing CPU intensive code when evaluating a logical expression which contains Lambda/Linq.

    bool flag = false;
    if( flag && )
    {

    }

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