Thread: expression execution order

  1. #1
    Registered User
    Join Date
    Jun 2003

    expression execution order

    I'd like to call a number of functions, all which can only be called if the previous function succeeded. All functions return bool results, so just wondering what the best way to do this would be.

    I'm currently using the following method:

    if (func_a())
       if (func_b())
          if (func_c())
    but wondering if this would be better:

    if (func_a() && func_b() && func_c())
    Problem is, would they all be called regardless of whether the previous one failed, or would execution stop when one of them returned FALSE? Or worse still, is the above unspecified, and depends on compiler?
    Last edited by _Elixia_; 10-02-2003 at 03:32 PM.

  2. #2
    Been here, done that.
    Join Date
    May 2003

    Re: expression execution order

    Use your first method

    The second method may not work in all compilers (if any), the first method is easier to read, debug, and maintain.
    Definition: Politics -- Latin, from
    poly meaning many and
    tics meaning blood sucking parasites
    -- Tom Smothers

  3. #3
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    The edge of the known universe
    The evaluation order of && and || is defined, otherwise things like

    if ( p && *p != 0 )
    would randomly fail if p was a NULL pointer

    if (func_a() && func_b() && func_c())
    would stop as soon as one of the funcs returned false, and those calls to the right would NOT happen.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

  4. #4
    Registered User
    Join Date
    Jun 2003
    Ok, thanks. Much appreciated!

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