Simple question about scope

This is a discussion on Simple question about scope within the C Programming forums, part of the General Programming Boards category; Hi all, I need to declare a variable that is only used in a do-while loop, and my question is ...

  1. #1
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    Simple question about scope

    Hi all,

    I need to declare a variable that is only used in a do-while loop, and my question is where to best declare and initialise it. I have been reading that it is best to declare variables at the inner most scope, and therefore in the case of do loops it will be like this:
    Code:
        do {
    
            double t = 0; /* variable declared and initialised inside the loop */
    
            statements;
    
        } while (expression);
    Because this is a loop, does this mean that "t" will be declared and initialised at every cycle?, or will it be declared and initialised only at the first cycle of the do loop?

    Obviously I could use this:
    Code:
        double t = 0; /* variable declared and initialised outside the loop */
    
        do {
    
            statements;
    
        } while (expression);
    but I am just wondering about declaring/initialising variables inside loops.


    Thanks,
    Spiros

  2. #2
    ... kermit's Avatar
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    Well, how about writing out some code and seeing what happens? In short, yes, i would be re-initialised to 0 every time through the loop, if it is inside of the loop body.

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    thanks for your reply, I think it was late at night when I posted this and was too tired to think straight... I guess sometimes it happens!

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    If you declare a variable inside of a loop, the compiler should throw an error, though it may only do it if the loop is going to go more than once. Sometimes you will need to initialize a variable to 0 several times throughout a loop. I have only done this a handful of times in the past.

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    Quote Originally Posted by madmax2006 View Post
    If you declare a variable inside of a loop, the compiler should throw an error, though it may only do it if the loop is going to go more than once. Sometimes you will need to initialize a variable to 0 several times throughout a loop. I have only done this a handful of times in the past.
    Everything in your post is false.
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  6. #6
    Algorithm Dissector iMalc's Avatar
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    Quote Originally Posted by bithub View Post
    Everything in your post is false.
    Well, maybe not everything. I'd believe that last sentence:
    Quote Originally Posted by madmax2006 View Post
    I have only done this a handful of times in the past.
    But yeah, none of the rest.

    Declare and initialise it inside the loop if it is only needed within the loop, and its value is not intended to be the same on every iteration, and it isn't needing to appear inside the while part (which comes just after the closing brace). Otherwise, declare and initialise it outside/before the loop.
    Last edited by iMalc; 09-14-2010 at 01:06 PM.
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