toupper(); or ||

This is a discussion on toupper(); or || within the C Programming forums, part of the General Programming Boards category; I was helping my brother with a program and he ended up having the program terminate by a do while ...

  1. #1
    Registered User linuxdude's Avatar
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    Mar 2003

    toupper(); or ||

    I was helping my brother with a program and he ended up having the program terminate by a do while loop. the while was
    while(YesNo=='Y' || YesNo=='y');
    I was thinking he would do what I do:
    I think my way is preferred, right?Also which one is better or faster

  2. #2
    C++ Witch laserlight's Avatar
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    Oct 2003
    Using the || should be faster, since you save on a function call for such a simple comparison.

  3. #3
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    Feb 2003
    I don't know what's "preferred" (& does it really matter what's preferred?) but his way will result in a smaller program (your way, you have to #include<ctype.h> and all the code that comes with it gets compiled into your program).

    Also, his way must be faster. If the value of YesNo is 'Y', his way finishes with a single test -- it doesn't even look past the ||. If YesNo is not 'Y', he finishes after the second test.

    Your way, in the best case, toupper() has to test to see if YesNo is an uppercase letter (I guess that takes 2 tests), then return to the main program to test if it's a 'Y'. So, it looks like there's at least 2 extra steps if it already contains 'Y' to begin with. If it's not an uppercase letter, it has to test again to see if it's a lowercase letter, then return whatever the uppercase equivalent is to the main program to be tested against 'Y'. Also, unless toupper() is implemented as a macro (I don't know whether it is or not), there is presumably some more time wasted calling the function.

  4. #4
    and the hat of int overfl Salem's Avatar
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    Aug 2001
    The edge of the known universe
    Go for what is most readable for you.

    The performance / space tradeoff's of such a simple piece of code are not worth worrying about.

    Find something really worth worrying about, like replacing a crummy bubblesort with a quicksort - that's where you'll get your real performance boosts.
    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.

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